© Andre Dib/WWF
Freshwater Species of the week

Freshwater ecosystems are home to an incredible diversity of species. Rivers, lakes, swamps, peatlands and all the other freshwater wetlands harbour more than 10% of the world's species. Each week, we will profile one of the most extraordinary.

© Christian Fischer


#195 White-faced darter

Native to the wetlands and peat bogs of northern from Europe to Northeast Asia, the white-faced darter, Leucorrhinia dubia, is a species of dragonfly that gets its name from their creamy white coloured faces. White-faced darters are active from April to September - a time known as their “flight period” where thousands can be seen flying. Their intricate markings makes them an iconic species among dragonfly enthusiasts - males have vivid orange and red markings while females have pale yellow markings. They breed in acidic waters laying their eggs in vegetation, commonly in sphagnum moss to save them from fish predation. White-faced darter nymphs have been shown to grow larger spines on their back when fish are present to avoid predation. Dragonfly species found in colder regions are particularly vulnerable to climate change. Climate change induced prolonged droughts threaten this species. The loss and degradation of peat bogs has led to the decline of white faced darters across its range but reintroduction programs are underway. They have been successfully introduced into areas where their habitats have been restored.

© Totti


#194 pink salmon

Pink Salmon, Oncorhynchus gorbuscha, are the smallest and most abundant species of Pacific Salmon. Pink salmon are found from the Sacramento River in California to the Mackenzie River in Canada and from the Lena River in Siberia to Korea and Honshu in Japan. They are also referred to as humpback salmon because males develop a pronounced humped back during their spawning migration. They are anadromous fish, meaning they migrate from freshwater to oceans when they hatch and back to freshwater to spawn. Males and females develop a vivid pink colouration during this time. Once upstream, females use their tails to dig a nest in the gravel of the streambed where they deposit their eggs. Males fertilise the eggs as they fall into the nest in the gravel. Small fish, birds and mammals feed on pink salmon in both freshwater and in the ocean. Bears feed on adult pink salmon when they are making their way up rivers to spawn. Pink salmon have immense ecological importance, providing sustenance for an array of different species and nutrients to the ecosystem when their bodies decay. In November, droughts across North America killed thousands of Pacific Salmon. They were trying to migrate upstream to their spawning grounds but could not make it due to unprecedented low water levels. Low water levels in streams and rivers combined with higher water temperatures can kill juvenile salmon and make it difficult for adults to swim upriver to their spawning grounds. Pink salmon are threatened by barriers to migration, habitat loss and climate change is compounding these existing pressures. 



#193 alligator snapping turtle

Endemic to rivers in the U.S. that drain out into the Gulf of Mexico, the Alligator Snapping Turtle, Macrochelys temminckii, is the largest freshwater turtle species in the world, weighing up to 90kg! They grow algae on their backs which helps them camouflage in muddy river beds. They hunt by staying motionless in the water and reveal an appendage on their tongue that looks like a worm to attract prey. Once the predator approached, they clamp down on them with their strong jaws and hooked beaks. They can stay underwater for 40-50 minutes before needing air. They prefer deeper beds of large rivers, canals and lakes. Alligator snapping turtles get their names from the ridges on their shells giving them a primitive dinosaur appearance. They are listed as Vulnerable by the IUCN Red List of Threatened Species. Alligator snapping turtles are threatened by habitat alteration, a growing international market for its meat, pollution and pesticides.



#192 Chinese fire belly newt

The Chinese fire belly newt, Cynops orientalis, is found in the lower reaches of the Yangtze River in the pools, ponds and paddy fields of Southern China. It has a bright red and orange belly signals predators to stay away, rightfully so as they release a toxin from their skin that can paralyse and even kill predators that try to consume them. During the day, they hide in the water between vegetation and rocks occasionally coming up to the surface to breathe. They can be found up to 2,000m above sea level, hibernating during colder months. During mating season, they can develop a blue sheen to their tail to attract a mate. Fire belly newts flick their tails to attract a mate. Between the months of March and July, they lay and hide their eggs in the water between aquatic vegetation. The larvae develop in the water and complete metamorphosis within a year.  They eat aquatic worms and insect larvae. Chinese fire belly newts are collected for local consumption and the international pet trade. Populations are suspected to be declining due to habitat degradation. Like many other freshwater species, more research to understand the population health of Chinese fire belly newts is needed.



#191 Imbabura Tree Frog

Native to the Pacific Lowlands of western Colombia and northwestern Ecuador, the Imbabura tree frog, Boana picturata, resides in vegetation close to streams. They are nocturnal, feeding at night in forests next to streams and waterfalls. They have extremely large eyes with a yellow iris which they blink very fast when eating enabling them to swallow faster. Their eyes put pressure on their mouth which pushes food into their throat. Like all tree frog species, they have toe pads to help them climb - making them excellent climbers! Their feet emit a wet mucus that allows them to cling to surfaces. They lay their eggs attached to vegetation in shallow, still water. Major threats to these species include agricultural development, human encroachment and pollution. Deforestation and pesticides also threaten the Imbabura tree frog. Luckily, its range overlaps with at least two protected areas in Ecuador. More research is needed on this species.



#190 Redtail catfish

Native to the Amazon, Orinoco and Essequibo river basins, the redtail catfish, Phractocephalus hemioliopterus, get their name from their orange-red dorsal and caudal fins but it has several different names throughout South America. In Guayna, it is known as the banana catfish, in Brazil as pirarara and in Venezuela as cajaro. The redtail catfish is one of the three giant catfish species in the Amazon next to the piraiba and the jau. They are bottom-dwellers that inhabit large rivers, lakes and streams, remaining motionless during the day and feeding at night on crustaceans and fallen fruit. Living fossils, their genus dates back to 13.5 million years old! Red tailed catfish are known for their long whiskers which have chemical reception cells used to sense smell. They can grow up to 56 kg big and live to 15 years old! They communicate with a clicking sound to ward off any potential danger such as river dolphins. Catfish make up the majority of river dolphins’ diet. However, mercury intake from catfish species threatens the health of river dolphins. It is important that we safeguard this species to in turn safeguard river dolphin populations.



#189 Common Apple Snail

The common apple snail, also known as the mystery snail, Pomacea bridgesii, is a freshwater snail native to Paraguay, Brazil and Bolivia and is found throughout the entire Amazon river system. They are one of the largest species of freshwater snail and are often found in lakes and rivers where oxygen levels are low. They are able to regenerate their eyes completely after amputation. Born with both gills and lungs, common apple snails frequently go to the surface to breathe using their syphon - a small tube used to breathe air. Unlike most snails, common apple snails are not hermaphrodites, meaning they have two genders. They lay 200-600 pink eggs above the water line. Once hatched, they are a tiny little speck that grows to the size of a pea in just a week! They are active during the night, searching for food which includes dead or rotting plants in the mud. Commons apple snails are popular in the aquarium pet trade and are threatened by urbanisation, habitat degradation and hydrological alterations. Further research is needed to evaluate the abundance of this species. 



#188 River Dolphins

River dolphins are extraordinary. They are the apex predators of some of the world’s largest river systems and are important indicators of the health of rivers. Where river dolphin populations are thriving, it is likely the whole freshwater system is flourishing. But all six species of river dolphins are threatened with extinction. A seventh river dolphin species, the Chinese river dolphin or baiji, was declared extinct in 2007, reminding us of how precarious these dolphins’ survival can be. River fragmentation due to water infrastructure divides populations; dolphins become entangled and killed in fishing gear; and water pollution affects the animals’ health. That is why on October 24th, we are bringing together the river dolphin range states to sign a historic Global Declaration for River Dolphins - spearheaded by WWF. The Declaration will help to accelerate action to save the world’s six remaining species of river dolphin - and enhance the health of their great rivers, benefiting the people and nature that depend on them. We need to safeguard these iconic animals that benefit both people and nature that depend on their rivers.



#187 Vampire Crab

The vampire crab, Geosesarma dennerleb, is a small crab species found in Java, Indonesia burrowing in muddy creek valleys in areas with dense vegetation. They are predominantly purple with a patch of yellow/cream colour on their back and bright yellow eyes. A nocturnal species, they feed on insects and plant matter during the night. These tiny crabs only grow up to 5cm big when adults. Some believe they are called vampire crabs due to their purple colour and yellow eyes that represent dracula. Males are slightly larger than females. The female will carry 20-80 fertilised eggs under her abdomen for a month until they hatch in freshwater. Females stay with them for several weeks until they are large enough to venture out on their own.  Once their body grows too big for their exoskeleton, like other crustaceans, the vampire crab will shed its exoskeleton and develop a new one. This happens around once a month. Since they are incredibly vulnerable while their exoskeleton is gone, they will go into hiding until they develop a new one. Their biggest threat is unsustainable harvesting as their attractive looks make them  popular in the aquarium pet trade.



#186 Climbing Galaxias

Native to south-eastern parts of Australia and all of New Zealand, the Climbing Galaxias, Galaxias brevipinnis, is known for its amazing ability to climb steep surfaces such as waterfalls and wet rocks using their downward facing pectoral and pelvic fins to “wriggle” upwards like lizards- making it one of the furthest inland penetrating fish species in New Zealand. A nocturnal species, Climbing Galaxias feed at night on aquatic invertebrates such as mayflies and small crustaceans. They lay eggs towards the surface close to vegetation and once hatched, the larvae are swept downstream into marine environments where they spend four to six months before returning back into estuarine and freshwater habitats. Threats to this species include artificial barriers to migration. Although climbing galaxias are known for their fantastic climbing skills, they struggle to navigate large and smooth man made barriers such as dams. In addition, habitat destruction, pollution of waterways, changes in catchment land use and the impacts of invasive non-native species are a risk to climbing galaxias. The natural distribution of this species is fragmented throughout its range most likely due to habitat fragmentation. There are currently no species specific conservation actions for this species. 



#185 Clown Featherback

Native to the Mekong and Chao Phraya river basins, the clown featherback, Chitala ornata, is a freshwater knifefish species found in lakes, swamps and the backwaters of rivers in Cambodia, Laos, Vietnam and Thailand. Clown featherbacks have five to ten black spots circled with white and have scale-less knife like bodies. They are nocturnal, hunting smaller fishes, crustaceans and insects at night. They darken their skin to communicate. They can breathe air through their modified swim bladders, meaning they are able to survive in low oxygen environments. Clown featherbacks have two nasal tentacles located above their mouth with sensory cells used to detect water movement and chemical signals within their environment used for navigation, to locate prey and detect predators. Females lay up to 10,000 eggs on floating vegetation and the males guard them until they hatch. Clown featherbacks can live up to ten years in the wild. They are commonly seen in dishes in Thailand and are the main fish used in the production of fish balls and patties. A commercially important aquaculture species, 500t/year of clown featherbacks are produced in the Mekong region. They are also heavily researched for the production of collagen which could increase the demand to use their skins in highly sought after beauty products. Overfishing and habitat degradation threatens this species.



#184 Greater Flamingo

The largest living species of flamingo, the Greater Flamingo, Phoenicopterus roseus, reside in mudflats and shallow coastal lagoons from West Africa, throughout the Mediterranean to Southwest and South Asia in addition to sub-Saharan Africa. They nest and roost on sand banks, mudflats, islands or boggy, open shores. They eat crustaceans, molluscs, insects, small fish, aquatic plants and algae. Greater flamingos get their unique colour specifically from the brine shrimp and algae. They are gray-brown until the age of two. Their necks have 19 bones which give them a lot of flexibility - they eat upside down scooping their beaks into the water. A highly social species, they nest in large colonies. They are monogamous - only laying one egg per breeding season. Juveniles migrate in response to water level changes. Flamingos are a hardy species that can survive in extreme temperatures (from -30C to 48C) and can be found in both fresh and saltwater. They have a gland that filters out saltwater and they usually rinse in freshwater afterwards. To attract a female, males perform a complicated dance swinging out their wings in one direction and one leg in another direction. Once they have mated, they are partners for life. Males and females both produce crop milk - taking turns feeding their offspring. Water pollution and habitat loss threatens this species. Lowering water levels negatively affects their food sources. It is important that we continue to protect wetlands used by this species.



#183 Water Buffalo

Wild water buffalos a.k.a. Asian buffalos, Bubalus arnee, are very dependent on the availability of water. Their preferred habitats are low lying grasslands and small sandy islands with braided river systems. A herbivorous species, their diet consists mainly of grass. Remnant populations of Wild Water Buffalo are thought to occur at single sites in Southern Nepal, Southern Bhutan, Western Thailand, Eastern Cambodia, Northern Myanmar, and at several sites in India. It is thought that the only true wild water buffalos exist in Sri Lanka. Water buffalos cool themselves in the water to regulate their body temperature because they don’t have sweat glands. They also go in the water to avoid being bitten by insects. They can be seen taking mud from the bottom of the river bed and throwing it on themselves. They have splayed hooves that allow them to move in the mud without sinking too deeply. Water buffalos have a gestation period of 10-11 months - meaning they are pregnant longer than humans! Now due to domestication, domesticated water buffalo can be found on every continent except Antarctica. In some parts of Brazil, police use water buffalo as transportation. The total population of wild water buffalo is less than 4,000 and they are listed as Endangered by the IUCN Red List of Threatened Species. They are believed to be extinct in Bangladesh, Peninsular Malaysia and the islands of Borneo, Sumatra and Java. Wild water buffalos are threatened by hunting, disease from livestock, genetic introgression from domestic buffaloes and habitat loss and degradation. 



#182 Spotted Handfish

Once widespread across Tasmania, the Spotted Handfish, Brachionichthys hirsutus, is now only found in the estuary of the Derwent River - making it an incredibly rare species. These slow moving fish have highly adapted pectoral fins which appear like hands, allowing them to walk along the floor. They rarely swim, using their anal and pectoral fins to propel upwards when they do. Found in shallow sandy and shell bottoms, Spotted Handfish reside in estuaries with low wave intensity. Spotted handfish are ambush predatory; like anglerfish species they have a lure above their mouth that attracts their prey: amphipods, shrimps and worms. It is thought that his lure is also used by males when performing a courtship ritual to attract a mate during mating season. They have been assessed as Critically Endangered by the IUCN Red List of Threatened Species. It is believed that habitat destruction and bycatch led to severe population declines in the 1980’s. Now their main threat is water pollution and the invasive species, the Northern Pacific Sea Star, which not only threatens spotted handfish themselves but also their eggs. Conservation measures are underway. The Australian and Tasmanian governments prohibit the capture of this species and mandate the development and funding of a recovery plan for this species. In addition, the Derwent Estuary Program is regularly monitoring the water quality of this estuary.



#181 Starry night harlequin toad

Thought to be extinct, the Starry night harlequin toad, Atelopus arsyecue, was rediscovered in Colombia's Sierra Nevada Santa Marta National Park in 2019. The National Park is home to the indigenous Arhuaco people of the Sogrome community who consider starry night harlequin toads to be a sacred species: guardians of water and symbols of fertility. This species is viewed as the authority of the natural world, serving as an indicator of when to plant crops or when to perform spiritual ceremonies. The Arhuaco people live in harmony with the toad, and have historically protected it along with its habitat and other wildlife that lives there. Starry night harlequin toads are found in the high altitudes (2,00-3,500m) and are given their name due to their distinctive black and white pattern on their bodies resembling a starry night in dark skies. They are less than 5 cm in size. Eggs are laid in fast flowing water where the tadpoles continue to develop. It is listed as Critically Endangered by the IUCN Red List of Threatened Species. They are threatened by habitat loss and degradation due to agricultural practices such as logging, fires and livestock in addition to the deadly chytrid fungus. Chytrid fungus is a major threat to amphibian species worldwide. To ensure their survival, improved protection inside and outside of the National Park is needed.



#180 Eurasian Beaver

Eurasian beavers, Castor fiber, are found throughout Europe and Asia. Eurasian beavers are found in freshwater woodland environments including rivers, streams, lakes and swamps. They have orange teeth due to iron in their enamel giving them the strength to gnaw through wood. Strong swimmers, they can hold their breath for up to 15 minutes and can swim up to 8 km/h - that’s double the speed of a human! Beavers fight climate change by helping control the flow of water. The dams they build increase the storage of water upstream and can help to create drought and fire resistant landscapes. They store food in the autumn to help them survive the winter. Beavers are perhaps the most famous ‘ecosystem engineer’ as their dam building alters the habitat and makes new habitat. Their dams are a nature based solution that process nutrients, traps sediments and creates wetland and floodplain habitats. As a result of conservation efforts, the Eurasian beaver has shown good recovery across its range. The highest numbers are found in Europe - where over 85% of Eurasian beavers are found. However, Northern Asian populations are very small and remain under threat. Eurasian beavers are threatened by hunting, habitat loss, especially from deforestation, dams blocking migratory routes and pollution. Thus, it is imperative that we have conservation measures in place in both Europe and Asia, such as the Norfolk Rivers Trust Beaver Project that is funded and supported by WWF.

© Mario Carvajal


#179 Macarenia clavigera

Endemic to Colombia’s Serrania de la Macarena National Park, Macarenia clavigera, Rhyncholacis clavigera, is an aquatic plant species famous for its vibrant red colour. The famous Colombian river, Caño Cristales, is known as the seven colour river - people travel from all over the world to see its vibrant colours from the Macarenia clavigera. It needs sunlight and a heavy influx of water to bloom, thus, it remains dormant during the dry season. Macarenia clavigera turns bright green in shaded areas and has even been seen in a range of colours from orange, yellow and blue -depending on the month, time of day or how much sunlight is coming through. It blooms in vast quantities on the rocks of the river beds and thrives in clear oxygen rich waters. Deforestation which decreases rainfall and water pollution threatens this species. It grows on top of  one of the oldest rock formations on the planet, the 1.7 billion years old rock formations known as the Guiana Shield. These rock formations are rich in minerals such as Phosphorus, Iron and Quartz that support the growth of the Macarenia clavigera. Environmental protection to protect this species in the area is firmly enforced. Only 200 people are allowed in the National Park per day, no sunscreen or insect repellent is allowed, swimming is only allowed in limited areas and during the dry season it is closed to allow the species to recover.



#178 Père David's Deer

Père David's deer, Elaphurus davidianus, also known as long-tailed deer or "four unlike," is endemic to China. Père David's deer is a large herbivore of the wetlands. They are good swimmers, preferring to live in the low-altitude swampy wetland with a mild climate. The wetland in the middle and lower reaches of the Yangtze River is an ideal habitat for them. Père David's deer have leathery tendon membranes that grow between their main hooves like duck flippers, which help with walking on muddy ground and swimming. They are a highly communal species. In summer, Père David's deer have a brownish-red coat; in winter, it is greyish-brown. Male deer have long horns, which are weapons for self-defence while female deer are hornless. Due to habitat loss and hunting, the wild Père David's deer became extinct in the 19th century and was listed as extinct in the wild by the IUCN Red List of Threatened Species. In 1865, a French zoologist and missionary, Pere David, discovered the deer in the Royal Hunting Park in Nanhaizi, Beijing. Since then, some of the deer have gone out of the country and stayed overseas. In 1894 and 1900, natural disasters and wars made the deer disappear from the Royal Parks and Gardens of the Qing Dynasty of China, and in the eight years before 1901, the 11th Duke of Belfort bought 18 Père David's deer from the Paris, Berlin, Cologne and Andean Zoological Gardens, and released them in his Ubonji Manor, so the population gradually recovered. After 1937, the deer from Ubonji began to be imported into zoos in some western countries for multi-point breeding. In the 1980s, the deer were reintroduced to the Nanhaizi Park in Beijing and the Dafeng Reserve in Jiangsu Province, China, where they were reintroduced to their native habitats to restore their breeding and wild populations. By 2022 there were more than 11,500 Père David's deer in China, of which nearly 5,000 are in wild populations. Currently, five wild populations of the deer have been restored in Jiangsu, Hubei, Hunan and Jiangxi provinces, where they were systematically released into nature and returned naturally to the wild in 1998. Further research needs to be conducted to assess the long-term viability of these existing wild populations.



#177 Black-winged stilt

Widespread across Europe, Asia and Africa, the Black-winged Stilt, Himantopus himantopus, resides in shallow freshwater and brackish wetlands, marshes and coastal lagoons. Their incredibly long pink legs make up 60% of their height. Making long migratory routes, they travel southwards between August and November and return to their breeding grounds in March and April. They feed mainly on insects and crustaceans and often nest in small groups. Black-winged stilts are very protective of their nests and will chase larger birds away from them if provoked. They nest in a small depression close to the water's edge where they lay 2-4 eggs - both males and females work together to incubate the eggs. Once hatched, they spend a month with their parents until they become independent. If a predator comes after their young, black-winged stilts will pretend to be injured to distract the predator. Black-winged stilts are protected through the Agreement on the Conservation of African-Eurasian Migratory Waterbirds, an agreement that focuses on conserving migratory bird species that are dependent on wetlands. But warmer temperatures and over abstraction have dried up wetlands pushing birds northward to find suitable wetlands for nesting. Increased conservation efforts to protect and restore wetlands are needed.



#176 Atlantic Mudskipper

Native to the brackish waters of the West African coast from Senegal to Angola, Atlantic mudskippers, Periophthalmus barbarus, are found in muddy substrates in estuaries, lagoons and mangrove swamps. As amphibious air breathers, they can skip, climb and  crawl using their pelvic and pectoral fins outside of water in search of food. They come out to feed at low tide on crabs, insects and mangroves on the surface of the mud. At high tide, they nestle back underwater into their burrows. Males dig burrows down to 1m deep where the female lays her eggs and guard them until they hatch. Atlantic mudskippers are gill breathers; when they walk on land they hold water in their gills and in addition, absorb oxygen through their skin and oral mucous membranes. Like frogs and toads, their eyes are placed high on their heads, giving them the ability to avoid predators above such as birds. Mudskippers are living model organisms suitable for the study of the evolutionary transition from water to land. Their ability to walk on land gives them the ability to exploit a novel terrestrial habitat that is hostile to their aquatic ancestors. They are harvested for human consumption, bait and the aquarium pet trade. Atlantic mudskippers are threatened by coastal developments, water pollution and destructive fishing practices. No conservation practices are known to be in place for this species.



#175 Bamboo shrimp

The bamboo shrimp, Atyopsis moluccensis, also referred to as the wood, flower, singapore wood, marble and Asian fan shrimp, are found from Sri Lanka through Thailand, Malaysia, Indonesia and possibly the Philippines. Found in fast flowing streams in upland areas, bamboo shrimp are found in a range of different colours, but are known for their distinct white stripe along their back. The colour of their body changes in congruence with their breeding season. Bamboo shrimp have two long sensory antennas giving them another set of eyes that help them sense their surroundings, used to locate food and avoid predators. They also have fans located on their four front legs which they use to capture passing food particles in high current areas. When in these strong currents, they cling to rocks and stones to avoid being stripped away. Bamboo shrimp are filter feeders, their diet consisting of microorganisms and plant particles. They shed their exoskeleton once a month. Once shed, they are vulnerable to predation and can be seen hiding under rocks and caves until their new exoskeleton hardens. They are popular in the aquarium pet trade and have now been introduced to the Mediterranean due to pet owners releasing them into the wild which could potentially threaten local species populations. Local populations of bamboo shrimps are threatened by extensive developments upstream that have polluted the waters.



#174 Common Fire Salamander

Common Fire Salamander a.k.a. European salamander, Salamandra salamandra, is endemic to Europe from Portugal to Bulgaria from lowland areas to up to 2500m. They are found in wet, cool areas near well shaded brooks and small rivers. In ancient times, people believed they were born in fires. Their bright yellow spots act to deter predators by signalling their toxicity. Fire salamanders have a toxin that causes muscle convulsions, hypertension and hyperventilation in all predators, if consumed. This is also true for humans, their toxins are only a threat if ingested. When threatened,they spray the toxins from glands behind their eyes into the eyes or mouth of the predator. Toxins are also secreted from their skin if a predator tries to eat or touch it. If a predator succeeds at taking one of their limbs, it can quickly  grow a new one. Fire salamanders take in oxygen through their moist, permeable skin. Females lay their eggs in the water where they young will reside until their gills turn into lungs. Local populations in Spain and Italy have declined due to habitat loss, introduced predator species and increased aridity. In addition, pollution of breeding sites by agrochemicals and predation by invasive salmonid fishes and American Crayfish threaten this species. A severe decline has been reported in the Netherlands. Bsal is an emerging fungal pathogen affecting amphibians and has been detected in Europe. There is an urgent need for research on EU wide approach and implementation of action plans to address the threat of Bsal on these salamanders.



#173 wood frog

The wood frog, Lithobates sylvaticus, is found in forested wetland and woodland habitats on the edge of ponds and streams in North America in both Canada and the United States. The wood frog has been proposed as the official state amphibian of New York. They have distinct black markings around their eyes that resemble a mask. Males make a chuckling or quacking sound during mating season. Eggs are laid and larvae develop in fish-free ponds. Wood frog tadpoles have the unique ability to identify their relatives - congregating together for protection. Adults assess the presence of fish in ponds and will change breeding locations to avoid predators. When inactive they hide under logs and leaf litter, camouflaging with their surroundings. Wood frogs can tolerate their blood and tissues freezing by producing an antifreeze substance that prevents ice from freezing within their cells. During this time, their body temperature typically goes down to -2℃ and they stop breathing and their hearts stop beating. They can stay frozen for weeks or even months! When winter ends, the frogs thaw and start feeding and mating again. Wood frogs may go through numerous freeze-thaw cycles throughout winter as soil temperatures rise and fall. An increase in frequency of these freeze-thaw cycles due to climate change threatens this species. In addition, extensive timber harvesting is a threat to wood frogs.



#172 Longnose gar

Found in large weedy lakes, backwaters and stagnant ponds, the Longnose Gar also known as Billy Gar, Lepisosteus osseus, is found on the North American Atlantic slope from the Delaware River, New Jersey to central Florida to Texas and a small part in Mexico. Longnose gars get their name from their overly long snouts, over twice the size of their heads. Gars have existed for 100 million years meaning they have been around since the time of dinosaurs. Their vascularized swim bladders allow them to breathe air which gives them the ability to survive in low oxygenated water. With razor sharp teeth, they feed on small fishes and crustaceans. Longnose gars are one of the fastest growing fish, growing six times faster than other common large freshwater fish and living 30+ years old. During the mating season, longnose gars migrate upstream to fast moving streams where they lay their eggs- laying up to 30,000 eggs! Gar eggs stick to aquatic plants and are toxic to animals and humans. Considered “trash fish” by some anglers, longnose gars have been left out to die on river banks due to their beliefs that they predate on popular sport fish and are unfit for consumption. The misunderstood longnose gar is an apex predator in aquatic ecosystems, important in maintaining stable fish populations and it’s fished more as a trophy fish than for consumption. Their thick scales, along with residing in schools protects them from predators. Their scales were valuable to Native Americans for tools, shields, arrowheads and ornaments. Native Americans consider the longnose gar a sacred fish - a symbol of strength and resilience. 



#171 Saimaa ringed seal

One of the world’s most endangered seals, the Saimaa ringed seal, Pusa hispida saimensis, are known as “classic” ice seals, they have well-developed claws that allow them to create breathing holes in the ice and a thick layer of blubber. The only existing populations of these seals are in Lake Saimaa, Finland. When the land rose after the last ice age, Saimaa ringed seals were separated from other ringed seal populations. They have lived in complete isolation from other ringed seals for roughly 9,500 years making them a morphologically different subspecies of ringed seals. Feeding exclusively on fish, the majority of their diet consists of perch, smelt Vendace and Ruff. Their average dive time for a long dive is 15 minutes! They build small caves in the snow where mothers give birth and where pups take refuge when they’re born. In the start of the 1980’s there were fewer than 120 individuals left but thanks to Parks and Wildlife Finland and WWF conservation work, the Saimaa ringed seal population has increased to 430-440 individuals. They are threatened by by-catch and reproductive failure due to mercury pollution. Climate change has negatively impacted pupping habitat due to poor snow and ice conditions. They are listed as Endangered by the IUCN Red List of Threatened Species. Ringed seals are protected by a variety of laws but within Europe legal provisions are not always fully enforced in domestic law. Volunteers with WWF Finland and Parks and Wildlife Finland are building snow banks for the seals to use during snowless winters. WWF educates residents of the Saimaa region on deal and net fishing bans and monitors how proposals are implemented.



#170 American Manatee

The American Manatee, also known as the West Indian Manatee, Trichechus manatus, is more closely related to elephants than any marine mammal. The largest aggregation of American manatees can be found in central and south Florida, USA and are famous in Florida’s Crystal River. Undertaking seasonal migrations, manatees are not residents there year round. They come in the winter in search of warmer waters. Legend has it that when Christopher Colombus came to the Americas he caught a glimpse of three mermaids that were not as pretty as he imagined - it was thought that he was referring to manatees. Manatees' preferred habitats are shallow grass beds with deep channels that are easy to access. Manatees are an indicator species for healthy ecosystems, responsible for controlling mosquito populations and maintaining vegetative balance. Feeding solely on vegetation, manatees are herbivores, eating more than 1/10th of their weight in food everyday. Manatees are such slow moving animals, algae and barnacles can be found on their backs. Manatees do not have a neck vertebrate so they are unable to turn their neck the way humans do. Although they are able to survive in freshwater, estuaries and marine environments, American manatees depend on freshwater for osmoregulation. Calves are dependent on their mothers for one to two years. Quiet protected areas are crucial for resting and for mothers with their calves. About half of their deaths can be attributed to collisions with watercraft. They are also threatened by habitat loss, reduction in natural spring flows and water temperature change - 246 manatees died in Florida during an abnormally cold winter. They are defined as Vulnerable by the IUCN Red List of Threatened Species. 



#169 Black Ghost Knifefish

Found in Venezuela, the Paraguay and Parana River and the Amazon Basin, the Black Ghost Knifefish, Apteronotus albifrons, are believed to be ghosts of the dead that take up their bodies when they die - hence their name. Black ghost knifefish are nocturnal and use an electric organ and receptors covering their body to locate their prey, navigate and communicate. But this shock can only be felt by smaller prey and is not harmful to humans. They have both a passive and active electrosystem along with a mechanosensory lateral line system detecting water disturbances created by the motion of their body. Females have a higher frequency than males - allowing potential mates to locate each other within river systems. Studies found that the gene in the ghost knifefish was duplicated 14.5 million years ago and acquired several mutations over the last 2 million years. This research could provide new clues about the genetics of epilepsy and certain muscle diseases. They don’t have scales and are completely black except for two white rings on its tail and a white spot on its nose. Using a fin under its body to move, it waves like a flag when it swims. Reaching up to 50 cm in length, adults have large mouths and are able to swallow small fish whole. They eat larvae, worms, small fish and insects. These unique species are popular in the aquarium pet trade. 

© Wikicommons


#168 Hairy-nosed Otter

One of the rarest otter species, hairy-nosed otters, Lutra sumatrana, are endemic to Southeast Asia and have been found in small pockets of Myanmar, and in parts of Cambodia and Viet Nam. Their name comes from the hairs you see on the tip of their snout. They reside in lowland wetland forests such as peatswamp, tropical and Melaleuca forests as well as mangroves and rivers. Living solitary or in groups of up to four, hairy nosed otters spend most of their day hunting for prey. They feed on fish, molluscs, crustaceans and water snakes. With fully webbed feet and a muscular body, they are great swimmers! They have long sensitive whiskers that help them detect changes in water movement aiding in navigation and hunting underwater. But populations are declining rapidly due to habitat destruction such as forest clearance for palm oil plantations and trade-driven illegal hunting. In Cambodia and Vietnam, hunting otters is common practice. They are hunted for their meat, illegal wildlife trade and for medicinal use. The hairy-nosed otter is the rarest of the Asian otters, and one of the rarest otters species in the world. In 1998 they were declared extinct but in 1999 they were rediscovered in the peat swamp forests of Thailand. They are listed as Endangered by the IUCN Red List of Threatened Species. Even though they are protected in all the range countries, populations continue to decline. More studies on their ecology, behaviour & populations are needed.



#167 Tralhoto

The Tralhoto, a.k.a. the four-eyed fish, Anableps anableps, is found in South America in Trinidad and in the coastal draingages from Venezuela across northern Brazil. It is abundant in mangrove estuarine areas such as the mouth of the Amazon River. They typically swim at the surface of the water so they can see both above and below the water at the same time. But don’t be fooled by their name. They in fact have two eyes divided by a thin layer of tissue each with its own cornea and pupil to catch light from above and below the water - allowing them to hunt both terrestrial and aquatic prey. On the surface, they hunt insects and below the surface they feed on smaller fish, algae and invertebrates. Four-eyed fish regularly make intertidal migrations. When the tide is high, they venture to the mangroves of the intertidal channels and when the tide is low it returns to the shallow waters of the permanent water channels, congregating in groups of up to 100 individuals. Their sex organs are located on either their right or left side so only left females can mate with right males and vice versa. This is believed to be an adaptation due to their unique mating behaviour. Females have a long gestation period of up to three months. A hardy species, they are able to adapt from freshwater to brackish to marine and can survive outside of the water for extended periods of time. But their mangrove habitats are threatened by erosion, coastal development and sea level rise.



#166 Slender-nosed Crocodile

Found in West and Central Africa, African slender nosed crocodiles can grow up to 4 metres long and weigh up to 220 kg. They reside in forested rivers and densely vegetated waters such as freshwater lagoons. With razor sharp teeth and powerful jaws well adapted to catching fish, they also consume birds, turtles and invertebrates. They hunt with just their eyes and nostrils above the surface. Their slender snouts act like tweezers - allowing them to get prey from small crevices. Swimming underwater using their tails, their eyes are protected by an extra set of semi transparent eyelids. Males show dominance by raising their bodies out of the water. Females show incredibly attentive prenatal care from helping the hatchlings out of their eggs. Once hatched, the female scoops the hatchlings into her jaw and carries them into the water. Incredibly wary  and susceptible to human disturbance, Africa slender nosed crocodiles are  listed as Critically Endangered by the IUCN Red List of Threatened Species. They are threatened by commercial skin hunting and habitat degradation.



#165 White-naped crane

Breeding on the border of Russia, Mongolia and China, white-naped cranes, Antigone vipio, are found on every continent except South America and Antarctica. In the winter, they migrate to the Yangtze River, the Korean Demilitarized Zone and Kyushu, Japan - as well as Kazakhstan and Taiwan. They are a popular symbol of the Korean New Year and commonly featured in art and folklore. They prefer breeding in areas where their nests can be concealed and where there is little grazing pressure - grassy marshlands, boggy upland wetlands, wetlands of steppe and steppe forest zones and wet sedge meadows.  During winter, it frequents freshwater lakes. With a high pitched, penetrating call, all cranes engage in dancing as a normal part of their motor development, being used not only in courtship but also to relieve tension and repair bonds. Loss of wetlands due to prolonged droughts and constructed dams threatens the white-naped crane. Development of agricultural land and pesticide pollution also threatens this species. Due to rapid on-going population decline, white-naped cranes are defined as Vulnerable to extinction by the IUCN Red List of Threatened Species. Suffering from rapid loss of habitat, WWF’s  Asian Flyways Initiative works to protect wetlands for migratory bird species such as the white-naped crane. Their future depends on resting and foraging sites along their migratory flyway. 



#164 Water Lettuce

First discovered in the Nile near Lake Victoria, water lettuce a.k.a. water cabbage, Pistia stratiotes, gets its name from resembling a leafy vegetable. It is thought to have originated from South America or Africa. Seen floating on the surface of lakes and rivers, the roots of water lettuce are free floating. Thus, it does not rely on soil to grow. Thick soft leaves that form a rosette and small white and pale green flowers bloom from late summer to fall. It is a valuable oxygenator, removes pollutants from water and provides shade and shelter for fish. The species can remove pollutants through a process called phytoextraction - the absorption of organics, salts and metals into their tissues. Water lettuce has an efficiency of 80-90% removal of heavy metals, nitrates and phosphate from wastewater. It has the ability to prevent harmful algal blooms as it outcompetes algae for nutrients in freshwater and blocks sunlight. It is also used as a food source for cattle. Some believe water lettuce has medicinal properties and is used as a laxative, treatment of bladder complaints, kidney disease, tumours and skin disease. It is also used for making soap in West Tropical Africa and can be used as biofuel. Water lettuce is also a crucial food source for wildlife including fishes, waterbirds and Manatees.The species has  been grown as an ornamental for lakes, ponds and gardens and with so many valuable traits, humans have introduced this species into regions outside its native range. This has negatively impacted biodiversity in these areas by crowding out native plants and it is currently being considered for the EU's list of banned invasive species. 



#163 Banded demoiselle

Found along slow moving streams and rivers from Western Europe to Western Mongolia, banded demoiselle, Calopteryx splendens, are colourful damselfly species often found on bankside plants or floating objects. Males have fully coloured wings with a metallic blue body and a large black spot on their wing -the black spot giving them their name “banded” demoiselle. Females have translucent bodies with pale green wings. Males are very territorial and court females by performing an aerial dance, showing off their colourful wings. Females lay eggs by injecting them into plant stems underwater. Eggs take two weeks to hatch. The larvae overwinter in the mud at the bottom of the river for two years until they fully develop. Once abundant throughout Europe, their populations declined in the 60s and 70s due to intensive stream management and water pollution. The populations have been recovering since the 90’s and now are defined as stable in Europe. However, more population information is needed about this species outside of Europe. Water pollution is the main threat to this species. In addition, intensive dredging, removal of bankside vegetation and over abstraction threaten the banded demoiselle. As populations of these species are still under debate, threats in certain areas may be more serious than previously thought.



#162 River Cooter

The River Cooter, Pseudemys concinna, is a freshwater turtle found in central and eastern United States and feeds exclusively on aquatic plants, grasses and algae. River cooters are easily spooked when approached and will quickly jump into the water. River cooters have large webbed feet which makes them excellent swimmers and gives them the ability to swim against strong currents. River cooters breathe underwater using a sac based on their tail called the cloaca bursae. This sac allows them to stay underwater for extended periods of time. During hibernation they can stay underwater at the bottom of lakes, rivers and ponds for up to two months! Generally solitary creatures, they sleep underwater under vegetation. However, they can also be seen basking on warm rocks and logs piled up on top of each other. They can live over 40 years old. Smaller than females, male cooters use extravagant displays to attract females, swimming around them and biting their backs. Small hatchling turtles are vulnerable and targeted by a variety of predators. River cooters are threatened by habitat loss, highway accidents and human consumption. They are also harvested from the wild and sold in pet stores.  More studies are needed to determine the population status and decline of this species. 

© Uzi Paz


#161 Hula painted frog

The Hula painted frog, Latonia nigriventer, was recently rediscovered in 2011 after not being seen for 56 years! Although good news, this species is still at high risk of extinction. With no close relatives, there is no other species like the Hula painted frog. Endemic to the Hula Valley in Israel, Hula painted frogs have dark bellows and small white spots. They are mainly nocturnal, burrowing into moist soil and leaf litter to hide from predators during the day. Diverging from all other amphibians 150 million years ago, they are living fossils. Hula painted frogs are closely tied to water. Their breeding season is from February to September. Found in lakes and swamps with dense vegetation cover, Hula painted frogs are threatened by habitat loss. In the 1950’s, the Huleh marshes were drained in an attempt to eradicate malaria and create suitable land for agricultural use. This species is Critically Endangered, with an estimated current population of around 250 individuals. They are threatened by habitat loss due to the drainage of marshland and pollution from pesticides and petrol. The species is protected by national legislation in the Hula Nature Reserve but further conservation efforts & research are needed to protect this species. A recent environmental DNA (eDNA) study has found evidence of this species has found an extant population confined in the south of the Hula Valley.

© Joe Walston


#160 Red river hog

The most colourful of the pig family, red river hogs spend most of their time wallowing in rivers, lakes and streams. Red River Hog, Potamochoerus porcus, is found near swamps and rivers in Africa from Senegal, through the Guinea-Congo forest and west of the Albertine Rift. Known for its reddish brown fur, both females and males have tusks from their canine teeth. They grunt or squeal to alarm others of predators in the area. Primarily nocturnal, they remain in densely covered areas during the day to avoid predators. Using their large muzzle to search for food in the soil, their diet consists mainly of roots, seeds and invertebrates. Red river hogs roam individually and in family groups ranging from 10-60. Strong swimmers, they can swim underwater holding their breath for up to 15 seconds. They mark their territory by using their tusks to scrape tree trunks. If threatened, they fight by butting heads. A highly adaptable species, red river hogs have been able to adjust to changing environmental conditions. Hunting has led to localised population declines and populations should be monitored in those areas. They are harvested for the bushmeat trade in most of Central Africa. In Senegal, sightings of red river hogs has become so rare that it is considered endangered and is a protected species by national law. More research on the population status of the red river hog is needed.



#159 Short finned eel

Native to Australia, New Zealand and the South Pacific, the short-finned eel, Anguilla australis,  have snake-like bodies and can reach up to 110 cm - They feed on crustaceans, molluscs, fish, aquatic insects and plants. They are thought to spend up to around 20 years in freshwater before they  migrate to the sea to spawn - only once before death. After their larval stage, they are transparent, giving them the name “glass eel.” Under some circumstances, young eels can navigate cascades when migrating within their  freshwater habitats, and on warm and damp nights they can travel short distances over moist ground - absorbing oxygen through their skin. An incredibly hardy species, they can endure long periods without food, burying themselves in the mud and entering an energy saving state when temperatures drop below 10 C. Short-finned eels are threatened by barriers to migration, habitat destruction, pollution and unsustainable exploitation. They are harvested and farmed on a global scale for consumption with an annual production of Anguillid eels estimated to be $US 1 billion. They are currently assessed as Near Threatened by the IUCN. However, there is no information regarding the population status of this species, and given harvesting and other risks, it is clear that more research is needed to determine distribution, harvest levels, abundance trends, as well as information on plausible threats.



#158 American Mink

The American mink, Neovison vison, is native to  North America and can be found in a broad range of habitats including lakes, streams, rivers, swamps and marshes. It prefers densely vegetated areas and dens under stones or the roots of trees and self-dug burrows beside the water. They are fiercely territorial over their dens and are able to slip into narrow openings to pursue prey. American mink are nocturnal and feed on fish, crustaceans, rodents, birds and frogs. Strong swimmers, mink have partially webbed feet and a thick waterproof oily coat that allows them to stay in the water for long periods of time. When searching for food they are able to reach depths down to 30m deep! Mink are members of the mustelid family and are related to otters, weasels and badgers. They have also been seen climbing trees. They purr like a cat when they are happy and hiss and spray foul odour when they are threatened. They usually live alone and are only with their partners during mating season. Among the most valuable fur animals, they are commonly hunted for their fur. Most of the mink fur used in commerce is produced in farms. A negative outcome of the fur trade is that American mink have been introduced by humans outside their native range, including in Europe. The adaptations which mink successful predators in their native homelands of North America, can pose a serious threat to wildlife that did not evolve to live with them, and therefore they are considered a risk to native wildlife where they have been artificially introduced. In their native range American mink are an important part of the ecosystem, but habitat destruction such as alteration to vegetation along rivers and wetlands and water pollution threatens this species.



#157 Emperor Newt

Emperor newt, (Tylototriton shanjing), a.k.a. Mandarin newt or Mandarin salamander, is a rough-skinned newt found in the Gaoligong Mountains National Nature Reserve, Yunnan Province, China. Shanjing means mountain demon in Mandarin, referring to their highly toxic skin. This little demon’s orange spots on its back are actually poison glands, which will release toxins when attacked - containing enough toxin to kill 7,500 mice! Tetrodotoxin is the neurotoxin released from their skin that can be deadly to humans if ingested. The bright colours of the bumps on its back are said to resemble the jewels of the crowns of the emperor. Underwater, its spots can be mistaken for light reflecting off pebbles. They live in pools and slow-moving streams in subtropical forests at an altitude between 1,000 m to 2,500 metres above sea level. Generally nocturnal, they feed on earthworms, snails, centipedes and small invertebrates at night. Females are larger than males and during mating, they circle each other underwater with their snouts touching. The female deposits eggs on rocks and plants in standing water bodies. The major threat is over-collecting for traditional medicine. Small numbers are ending up in the pet trade, and its habitats have been lost and are threatened by further development for human settlement. Defined as Vulnerable by the IUCN.



#156 Common Pipewort

Found in the shallow water of lakes, ponds, marshes, wetlands and slow moving rivers, the Common Pipewort, Eriocaulon aquaticum, a.k.a the seven angle pipewort has blooms of tiny flowers held up above the water line attracting pollinating insects. While many aquatic plants are wind or water pollinated, pipeworts have a nectar gland at the tip of each petal to attract pollinators. Widespread across North America and Canada, pipeworts have a tall leafless stem with a button-like white flower. The part of the plant submerged underwater provides a habitat for invertebrates, which are  in turn  a food source  for aquatic species. Beetles also feed on the roots and shoots. Their height depends on the water depth  it is growing in - up to several feet high! Pipeworts improve water quality by transporting oxygen to its underwater roots, stems and leaves. This oxygen leaks into surrounding spaces where microorganisms decompose organic wastes, very similar to a water treatment plant. Populations of pipeworts have declined globally, mainly threatened by shoreline development and pollution.

© Jorg Freyhof


#155 Freshwater Blenny

The freshwater blenny, Salaris fluviatilis, is found in Morocco and Algeria, widespread across Europe and is also found in Turkey and Israel. As a bottom-dwelling fish species it likes gravel and rubble substrate with moderate to high current velocity. Populations are generally small and highly localised. Generally reclusive, they protect themselves from predators using their brown mottled skin that blends in with the rocks. Males make nests under large stones where they attract females for spawning. The females lay the eggs and the male guards them against predators until they hatch. Threats to this species include eutrophication, gravel extraction and habitat destruction. In addition, dams and the channelization of rivers have fragmented rivers and water extraction and drought may hamper reproduction. Life-history traits of the freshwater blenny suggest that it may be vulnerable to more severe drought conditions. In five of the nine Mediterranean countries they are classified as vulnerable or endangered. The removal of gravel and stones from rivers for the construction industry threatens the freshwater blenny due to their very specific nesting requirements. Water pollution, especially from urban wastewater and the introduction of non-native species also threaten the freshwater blenny.



#154 Red Line Dwarf Cichlid

Native to the Orinoco Basin in South America, the Red Line Dwarf Cichlid Dwarf, Apistogramma hongsloi, typically live in small slow-moving streams. Known as Viejita in Colombia, this colourful dwarf cichlid can be found in many streams of the Orinoco River basin, especially the ones between the Sipapo and Cuchivero Rivers. Part of its distribution lies in El Tuparro National Park in Colombia and in the RAMSAR protected wetland of the Bita River. Males have red markings distinguishing them from other Apistogramma species. In the breeding periods, males spend much of their time flashing their fins at each other and displaying brilliant colours. In the sunny sections, the river banks are heavily planted and the light-coloured sand is covered in periphyton. These sunny spots are where you can find many Red Line Dwarf Cichlids gulping up the sand, sifting through it, and spitting out the inedible matter. Females maintain their distance and are usually more inconspicuous, hiding under  leaf litter or between the aquatic plants. Sexually dimorphic, males and females differ in colour and the males are larger than females. Highly sought after by aquarists, this species is found in people’s aquariums around the world. There is no estimated population size of this species, however it faces a number of threats including habitat loss, water pollution and overharvesting. There is a need to understand the population size, distribution and trends to better protect this species.



#153 Bakara Sulawesi elephant snail

The Bakara Sulawesi elephant snails, Tylomelania bakara, are endemic to Sulawesi, Indonesia. They are often referred to as rabbit snails due to their drooping antennas resembling long rabbit ears. Most of them occur in the ‘ancient lakes’ of Sulawesi in the region of Tanjung Bakara in Lake Towuti. A rock dwelling freshwater lake species, they can be found at a depth between 2-20m in 27-30℃ feeding on algae. Recognized by their distinct shell shape, they can grow as long as a man’s  finger. Studies have found that they have originated as far back as 5.4 million years ago. Bakara Sulawesi elephant snails lay eggs every 4-6 weeks with each egg sack containing 1-2 baby snails. Like most snail species, they become immobile and hide in their shell when they sense danger. They are threatened by nickel mining and hydropower dam installations which impact natural water fluctuations in the lake. Many species of Tylomelania are collected for the aquarium pet trade. Harvesting could cause a very rapid decline of this species due to its already very limited distribution. They are currently listed as Critically Endangered by the IUCN Red List of Threatened SpeciesTM based on its extremely limited distribution and continuing deterioration of habitats. A major project initiated by Shoal Conservation to establish a management and action with local governments, communities and the private sector to protect the ancient lakes of Sulawesi is underway aiming to highlight key areas for conservation.



#152 Common Carp

The Common Carp, Cyprinus carpio, is a widespread freshwater fish species native to eastern Europe and central Asia in the rivers that drain into the Black, Caspian and Aral Seas, but has been introduced into freshwater habitats around the world for food and sport fishing. Common carp found in the Danube River 2000 years ago were kept in specially built ponds by the Romans for consumption. At the same time, it was the first fish species domesticated in China. Both European and Asian subspecies have been farmed and  spread by monks between the 13th and 16th centuries. The Common Carp is one of the major species produced in world aquaculture. Worldwide more than four million tons of common carp are produced annually in aquaculture - making them one of the most economically important fish species. Carps are one of the four species that account for 85% of total inland water catches. Although gregarious (one fish can lay over a million eggs in a year) common carp  populations have declined by 30% in their native range due to river habitat modification including  channelisation which removes in-river habitat and disconnects river from their floodplains, and the installation of dams, which literally cut rivers in half. As Common Carp are naturally potadromous (migrate within rivers to complete their life cycle) and require flood plain  areas to spawn, river modifications are a significant threat. Furthermore, hybridisation with farmed fish is a threat to this species. They are defined as Vulnerable by the IUCN Red List of Threatened SpeciesTM.



#151 Common Yabby

The Common Yabby, Cherax destructor, is a crayfish species endemic to Australia and found as far south as Tasmania. The word Yabby comes from the Wemba Wemba Australian aboriginal language. The most widespread species of freshwater crayfish, the Common Yabby, is found in swamps, dams, streams and rivers. As all crustaceans, they have no skeleton but a hard exterior shell known as an exoskeleton. Opportunistic feeders, they are omnivorous - feasting on just about anything including themselves - cannibalistic when insufficient food is available. They can grow up to 30 cm long and their colour varies based on which season they are found, and can also vary from individual to individual found in the same location. Most commonly found in a drab olive, dun or light brown colour, they have also been found to range from black, ochre-yellow and brown to red and blue. Yabbies grow by moulting, shedding of their shell - they will take up water and store it within their body tissues to expand their new shell. The Common Yabby can survive in temperatures ranging from 1C to 35C. They can dig burrows down to 50 cm deep - allowing them access to water in the shafts during dry spells in the summer. Found in areas where oxygen levels are high and there is plenty of vegetation. Listed as Vulnerable by the IUCN Red List of Species ™.



#150 Hawaiian freshwater goby

The O’Opu or Hawaiian freshwater goby, Lentipes concolor, can’t move mountains, but they sure can climb them! More accurately, they can climb the waterfalls of mountain streams of Hawaii, where they are endemic. They use suction disks on their ventral sides formed by the fusion of pelvic fins to climb the wet rocks behind waterfalls, even scaling the 135 m Akaka Falls. Studies show that the O’Opu can reach fast flowing upper stream segments and the elevated suction pressure enhances its ability to successfully capture food. They also need these continuously flowing streams for critical reproductive periods - they are amphidromous, meaning their life cycle is split between freshwater and marine environments, which has enabled them to avoid the inevitable extinction that would befall landlocked fishes in streams destroyed by volcanism or erosion. Adults live in freshwater, where they spawn, and once the larvae hatch, they are washed into the ocean to feed. After metamorphosis, juveniles migrate back to the streams to live the rest of their adult life. Males have black heads and orange tails, while females an olive to brown colour. But both have bright blue eyes. Culturally important, the Hawaiian freshwater goby is food fish for Hawaiians. They were cultivated in aquaculture in the 16th century and aided in the production of the root vegetable, Taro by pruning the leaves and removing pests- a win-win for aquaculture and agriculture. As a narrow-range endemic species, with a unique life cycle, like other pacific island gobies, the Hawaiian freshwater goby is particularly sensitive to anthropogenic changes that may disrupt stream flows, such as channelisation, dams, and water diversions. Assessed as Data Deficient by IUCN Red List, this intriguing species urgently needs more study.



#149 Dog faced water snake

The dog faced water snake, Cerberus rynchops, also known as the bockadam snake is native to South and Southeast Asia. Found in mangrove forests, mudflats, tidal creeks, estuaries and rivers, they have flattened tails and very small  strongly keeled scales that help them to swim better. Their valvular nostrils create a watertight seal that allows them to live underwater without inhaling or drinking too much water. They have salt secreting glands enabling them to distil the water they take in. Well camouflaged, the dog faced water snake blends in well with mud and litter. The name dog faced water snake is due to their large head and snout. Once born, they are independent from their parents. They are rear fanged and mildly venomous. Dog faced snakes have been seen jumping across mudflats using a sidewinding technique.They are nocturnal, feeding at night mainly on small fish, crustaceans and frogs. They hunt in shallow water and often hide under the mud. They were historically traded and used for their skin in the Philippines. While this is no longer the case in the Philippines, it is possible that they are still collected for the leather trade in some countries. Known for their bright orange and yellow bellies which mostly occurs in females. Its eyes are located at the top of their heads, allowing them to see while half-submerged and hidden in the mud while still watching for prey or predators. Although assessed as Least Concern by the IUCN Red List of Species ™, the species has localised threats, in particular in its preferred mangrove habitats. 

© Shutterstock / Rocchas / WWF


#148 White-tailed Eagle

Appearing in Germany’s coat of arms, the White-tailed Eagle, Haliaeetus albicilla, has one of the largest wingspan of any eagle in the world - up to 2.5m! Living most of the year near large bodies of water, the White-tailed Eagle can be found both on coastlines and inland freshwater areas. Found across Eurasia as far west as Greenland and as far east as Japan, the white-tailed eagle has strongholds in Norway and Russia. Spending most of their day perched on trees, they require forested areas and access to lakes, wetlands, rivers and marshes. Opportunistic feeders, they snatch food from birds and otters but they are also excellent fishers, taking  fish at the surface of the water, where they can reach speeds of up to 70 km/hr. Nests (known as ‘eyries’) are built from mature trees, branches and twigs  and can be up to 2m wide. Females lay 1-3 eggs, and for the first three weeks after hatching, males do all of the hunting. Their offspring leave after 70 days but they are dependent on their parents for 5-6 more weeks. Destruction of wetlands and poisoning from pesticides threaten the white-tailed eagle. Conservation measures such as protecting eyries, providing safe food and re-introduction into specific areas have been put into place. In addition, conservation actions such as adaptive management of wind farms (turning them off during migration periods), preserving perch trees and encouraging use of lead-free ammunition in hunting should be put into place to safeguard this species.

© WWF Christian Ziegler


#147 Freshwater Crab

Found in lakes, rivers and streams throughout Southern Europe, the freshwater crab, Potamon fluviatile, only resides in freshwater areas. Feeding at night either in the water or on land, they are aggressive using their right claw to attack, the majority being right-handed. Young crabs are more aquatic than adults. An omnivorous species, they feed on worms, insects, shrimps, small fish, amphibians and algae. They hide under stones and vegetation for shelter as well as dig burrows under banks - up to 80 cm deep! From November to February, they hibernate in burrows or natural refuges. Females are generally smaller than males and individuals can live up to 12 years. They have very few predators - their main threat being humans - individuals catching 3,000-10,000 per season. Threatened by pollution, habitat degradation and over harvesting, these European freshwater crabs are listed as Near Threatened by the IUCN. The survival of these crabs relies heavily on habitat protection and preservation of freshwater ecosystems as they use burrows and vegetation to seek refuge from predators. With the Convention on Biological Diversity (CBD) COP coming up next week, it is critical that leaders recognise the importance of safeguarding freshwater biodiversity.

© US Fish & Wildlife


#146 American Paddlefish

Living fossils, American paddlefish, Polyodon spathula, date back to 125 million years ago and are found from the Mississippi basin to New York to Montana and South to the Gulf of Mexico. A species of ray-finned fish closely related to the sturgeon, paddlefish are also harvested for their meat and caviar as an alternative to sturgeon. As filter-feeders, their constant grazing on tiny aquatic organisms helps keep their populations in check with zooplankton as their primary food source. Its snout extends 1/3 of its body length - which is covered with thousands of electroreceptors to locate zooplankton and facilitate migratory behaviour. With undeveloped eyes, they also rely on these electrical receptors for navigation. American paddlefish can grow up to 2 metres long and weigh up to 90kg! Requiring open, free flowing rivers, paddlefish populations have declined due to stream channelisation, levee construction and drainage of bottomlands. Dams prevent paddlefish from being able to move upstream to their spawning territory. The American paddlefish is the only living relative of the Chinese paddlefish, which has recently been declared Extinct by IUCN. Paddlefish populations have declined due to overfishing, pollution, barriers to migration and habitat destruction and are listed as Vulnerable by the IUCN. The American paddlefish is the only member of its family left on Earth. Control of sport and commercial fishing through federal regulations have helped bring back populations and other conservation measures that increase fish passage are being considered.

© David Lawson WWF


#145 Asian small clawed otter

The smallest otter species in the world, the Asian small clawed otter, Amblonyx cinereus, hardly reach 5 kg and are found in South and Southeast Asia. Asian small clawed otters are playful, social animals forming small family groups. Very adaptable, they are found in mangrove & peat forests, swamps, fast flowing and stagnant waters. They require plenty of vegetation for protection and shade. They are also found in rice paddy fields feeding on crabs which is seen as an asset to rice farmers as crabs are pests to their rice paddy fields. They are excellent swimmers, they start swimming at 3 months old by using their back legs and tails. They have two layers of fur with the outer layer being waterproof. Air gets trapped between their two layers of fur which keeps them buoyant in the water. After swimming, they rub up against logs and vegetation to mark their scent - individuals have distinct scents as humans do with fingerprints! Massive destruction of wetland forests across their range, including in Indonesia, and conversion into palm oil plantations in Sabah, has resulted in significant habitat loss for this species. Threatened by habitat loss, pollution and hunting, the Asian small clawed otter is listed as Vulnerable by the IUCN. Protecting and restoring resilience across entire river basins including their deltas is crucial in mitigating biodiversity loss. Find out more about our resilient asian deltas initiative in the freshwater practice and what we are doing to protect and restore Asian deltas.

© Tiit Hunt


#144 European River Lamprey

The ancient migratory freshwater species, the European river lamprey, Lampetra fluviatilis, come from the lamprey family which were the first fish to evolve 530 million years ago. European river lampreys are jawless fish, characterised by a funnel-like sucking mouth with teeth - boring into the flesh of other fish and feeding on bodily fluids. Resembling eels, they have a strong flexible cartilage instead of bone and have an average length of 30 cm. Their reproductive cycle is similar to a salmon, hatching in rivers, going to the sea to feed and migrating back into rivers for spawning from autumn to spring. Adults die after spawning -laying up to 25,000 eggs! The larvae spend several years in soft sediment before migrating back to the sea. The construction of dams has reduced their numbers as they are unable to move upstream to their spawning grounds. Worldwide rivers have been fragmented by dams and other hydraulic structures contributing to freshwater biodiversity loss. River lampreys are poor swimmers, thus, not well-adapted to pass barriers. In almost every watershed, lamprey habitats are fragmented. Maintaining connectivity between freshwater spawning and rearing habitats and estuarine/ocean feeding areas is crucial for river lamprey species. In Spain, the river lamprey has been declared officially extinct since 2018. Find out more about dam removal projects in the EU to protect freshwater migratory species like the river lamprey. Allowing free flowing rivers is essential to preventing biodiversity loss in our freshwater ecosystems.

© Bernard Dupont


#143 Nile Monitor

The second largest reptile found in the Nile, the Nile Monitor, Varanus niloticus, can weigh up to 20 kg. Highly adaptable creatures, they can be found along the Nile in sub-Saharan Africa in forest, savanna, woodland, bushland, varied aquatic habitats from mangroves to lakes and rivers. Highly aquatic, Nile monitors thrive around rivers and lakes, they spend most of their time in the water - with the ability to remain underwater for up to 15 minutes! They are strong, active swimmers and when they sense danger, they can be seen leaping from tree branches into the water. Nile monitors are known for their muscular bodies, strong legs, powerful jaws and muscular tails shaped like rudders that aid them with swimming. During the day, they can be seen basking on the shoreline and at night they are found sleeping in burrows, submerged in water or on tree branches. Generally solitary animals, Nile monitors rarely interact with each other outside breeding season where males and females mate with multiple partners. Nile monitors are important predators, controlling populations of various prey species such as crocodiles as they feed on crocodile eggs. The main threats to Nile monitors are the pet trade and hunting for food, leather and traditional medicine.



#142 Magdalena Turtle

The prehistoric-looking freshwater turtle known as the Magdalena river turtle or Podocnemis lewyana, is endemic to Colombia, distinct to the Magdalena and Sinu Rivers, but also found in the San Jorge and Cauca River. They diverged from other turtles over 100 million years ago - around the same time humans shared a common ancestor with bats & tigers! Among freshwater turtles they have some of the longest aquatic migratory patterns rarely leaving the water except to bask. Primarily found along the banks of rivers, they are also found in flooded areas connected to rivers where they spend their time basking in the sun. Nesting occurs twice a year during low water level periods on gravel or sand beaches as well as banks and pastures when river levels are low - laying an average of 22 eggs. Adult females are larger than males, weighing up to 8kg and 500mm in length. Locals see these turtles as a source of protein and believe that consuming them provides medicinal benefits such as curing diseases and recovering from pregnancy. Magdalena river turtles are threatened by habitat destruction and pollution, hydrological changes due to dams, traditional consumption and commercial exploitation. The consumption of turtle meat during Lent is deeply rooted in northwestern Colombia’s culture - with over a million turtles thought to be consumed during this period! Populations have declined over 80% in the last 25 years, listed as Critically Endangered by the IUCN. Exploitation of the Magdalena river turtle is prohibited in Colombia, however it is often unenforced.



#141 Proboscis monkey

The Proboscis monkey, Nasalis larvatus, resides in mangrove, peat swamp and freshwater swamp forests - rarely straying away from water. They are known for their unusual appearance with diverse colour patterns of orange, yellow and pink and are distinguished by their long noses - up to 17 cm long! Their noses help them produce loud bellowing sounds to raise alarm and attract females. They are endemic to the island of Borneo, where is distributed on both the Malaysian and Indonesian sides of the island, including in rivers such as the Kinabatangan and Mahakam. Among primates, Proboscis monkeys are the primate world’s most prolific swimmers - seen frequently swimming across rivers and distances of up to 20m underwater. They have evolved webbed feet and hands, allowing them to outrun crocodiles at times. Proboscis monkeys leap into the water, doing one of their comical belly flops, and are able to take deep dives when they feel threatened. Highly social animals, they form troops of 2-30 with a male leader and can be seen together resting and sleeping on mangroves at the edge of the water. In order to get enough energy, they have to eat large amounts of leaves and unripe fruits which enlarge their stomachs - giving them their pot bellies. Due to hunting and habitat destruction, Proboscis monkey populations have declined drastically. Populations have declined by 70% over the last 36 years. The infamous Borneo forest fires and clearing of forests for palm oil plantations have been major contributors to their decline. They are listed as Endangered by the IUCN. They are currently protected in Borneo.

© Martin Harvey WWF


#140 Pygmy Hippo

The Pygmy hippopotamus, Choeropsis liberiensis, are the smallest species of the hippo family that are reclusive and nocturnal. They are half the size of and weigh ten times less than the Common Hippo. They rely on freshwater to keep their skin moist and their temperature cool. Pygmy hippos are solitary animals - only when a female is accompanied by their young or briefly during breeding are they seen as a pair. They spend roughly 6 hours a day feeding on terrestrial and semi-aquatic plants and spend the day hidden in swamps, wallows and hollows under the banks of streams. Pygmy hippos follow well-defined trails which they mark by vigorously wagging their tail while defecating. Their closest living relatives are whales and dolphins and hippopotamus is derived from the Greek word “river horse”, as it spends its time in rivers and swamps, with  its nose and ears close underwater. Featured in folktales, Pygmy hippos find their way through the forest by carrying a diamond in its mouth to light up its path and they must be caught at night to take the diamond. Deforestation due to palm oil plantations, cultivation and mining and logging, has destroyed their habitat. In addition to habitat loss, increasing hunting intensity has threatened the Pygmy Hippo populations - with only a few thousand left in the wild. They are listed as Endangered by the IUCN. Remaining Pygmy Hippo populations are fully protected in all state range countries and are mainly found in protected areas.

© Martin Harvey WWF


#139 African Bullfrog

The African Bullfrog, is also known as the Pixie frog due to its scientific name, Pyxicephalus adspersus. It is among the largest of the frogs on the planet, with males weighing up to 1.4 kilos and measuring up to 24.5 cm in length - the size of a dinner plate! Females are half the size of males, which is unusual as female amphibians are generally larger. Found widely in South Africa, Swaziland, Namibia, Botswana, and Zimbabwe, they also extend north to southern Angola, Zambia, Malawi, Mozambique, Tanzania, and Kenya. They are also one of the most adaptable amphibians on Earth - able to survive the harshest African environments. When living in areas that are completely dry for years, with temperatures ranging from 0 - 40 ℃, African Bullfrogs burrow underground, forming a tough cocoon called an estivation chamber. They are only active during the rainy season, waiting it out for six to ten months -  spending most of their lives estivating underground. As carnivores, their diet consists of small rodents, small birds, reptiles, invertebrates and insects. But they are also a cannibalistic species - male African Bullfrogs are known for eating their own tadpoles, which they guard. During breeding season males congregate in large groups displaying aggressive behaviour such as pushing, biting and even consuming smaller males. Large males push their way to the centre to begin their mating call and females dive towards the dominant males. Once fertilised, females release as many as 4,000 eggs! African Bullfrogs are harvested for local consumption and caught for the commercial pet trade. Some populations are declining in South Africa due to loss of their breeding habitats. 

© Alejandro Calzada


#138 Granular Salamander

Found in subtropical and tropical high-altitude grasslands, freshwater marshes and ponds, the granular salamander, Ambystoma granulosum is a species of mole salamander only found in a small area of central Mexico close to Toluca in Mexico State - 3000 metres above sea level. Mole salamanders diverged from all other salamanders in the Late Jurassic period - over 150 million years ago! These amphibians live around 5 years and breed in marshes, dams and small ponds. They are a metamorphosing species giving them the advantage of reproducing in aquatic environments, swapping out their gills and fins present in their larval stage for eyelids and lungs in their adult stage. Thus, spending the majority of their lifetime on land in grasslands and returning to freshwater to breed yearly and feed. They are threatened by habitat loss, pollution and overcropping due to forest clearance and water extraction by extensive urban and agricultural expansion. Due to low food availability, Granular salamanders experience high mortality rates in their early life stages. Non-native predatory fish are also a major threat to these salamanders. The granular salamander is classified by the IUCN as Endangered as the species has declined over 50% in the last 25 years. Conservation and restoration of the Granular Salamander's habitat is urgently needed.

© Zsolt Varanka Photography


#137 Tisza Mayfly

Flying over the Tisza River, Tisza mayflies are aquatic insects named after this transboundary river that flows through Hungary & Serbia where it meets the Danube. Tisza mayflies, Palingenia longicauda, are also known as the Long-tailed mayfly and Giant mayfly because they are the largest of the mayfly species, measuring 12 cm from head to tail. Never moving away from water, they fly low, often touching the surface of the water. “Blooming of Tisza” has become a tourist attraction during a week in June, where Tisza mayfly larvae hatch. The spectacular synchronised swarming of  millions of these aquatic insects can be seen just above the water’s surface, frantically trying to mate after hatching as they only have a few hours to mate before they die. The Tisza mayfly has become a symbol of freshwater conservation efforts in Central Europe, especially in Hungary - their  presence is a sign of clear unpolluted water, promoting healthy rivers. This species used to be widespread in medium-large rivers throughout Europe but have experienced 98% range loss in the past century. The Tisza mayfly has dramatically declined due to rapid, intensive hydromorphological alteration and pollution of European rivers that peaked around 1930. It’s now extinct from the Loire (France), the Rhine (Germany), and the Danube (Serbia and Bulgaria). Conservation efforts are underway to protect these aquatic insects in their native habitats in Hungary as well as repopulating the Rhine in Germany. 

© Ryan Francis


#136 Spangled Perch

As Australia’s most widespread native freshwater fish, the Spangled Perch a.k.a  the Spangled Grunter or Jewel Perch, can grow up to 25 cm in length. Leiopotherapon unicolor is naturally found in the freshwater systems in Northern Australia such as the Murchison River, Hunter River, Murray-Darling system as well as the Lake Eyre/Bulloo-Bancania Drainage System. They like swimming in a wide range of waters with little vegetation such as rivers, lakes, dams, billabongs, bore drains, wells and waterholes. This hardy species can survive severe dry periods, found in wet sand after surface water has dried up. It can also tolerate a wide range of temperatures and salinity levels. The spangled perch has a high dispersal rate and the ability to colonise less accessible habitats quickly. Labelled as an extreme dispersal species, this species moves up to 300 km after a flooding event. Females spawn 24,000 to 113,000 eggs allowing their populations to multiply quickly. As opportunistic feeders, the spangled perch have a diverse range of prey including small aquatic insects, fish, molluscs (eg. water snails), crustaceans (eg. shrimps) and plant matter. They are highly adaptable to new environments and can attack a wide range of native aquatic life. Spangled perch can potentially have a highly destructive impact on native species if introduced into waters outside of their range. The Spangled Perch is listed as Least Concern by the IUCN.

© Derek Keats, CC BY 2.0 (https://creativecommons.org/licenses/by/2.0/)


#135 Spotted-necked otter

Spotted-necked otters, Lutra maculicollis, are known for their namesake and distinctive spots around their neck and upper lip. They are one of the four mammal species native to Africa's Mara River and throughout sub-Saharan countries from Guinea Bissau to southwest Ethiopia and southeastern South Africa. As cubs, they are very dependent and may stay with their mother for up to two years. While typically solitary, for a portion of the year spotted-necked otters live in small family groups and enjoy playing with each other. Social life provides some advantages: foraging in loosely-knit groups of around 20 allows them to catch prey - frogs, crabs, small water birds, and especially fish - easier. They are considered the most aquatic African otter, as they are well adapted to their freshwater environment, rarely moving more than 10 m away from water. They require permanent water sources with high fish densities, which they catch with their sharp claws while swimming with fully webbed paws. Able to dive down to depths of 14 m, they can spend 4-6 hours underwater daily. Because they are diurnal and mainly hunt by sight, they need clear unpolluted water. Vegetative cover such as long reeds, bushes, and grass along the shoreline are also essential to provide cover for resting and denning. Listed as Near Threatened by the IUCN, they face threats such as habitat loss, fishing conflicts, fish nets, and poaching. Non-native species like the Nile perch are a potential threat to the Spotted-necked otter because they push the smaller local species to the brink of extinction, threatening their food supply.

© Mikolji



Leaf or a fish? When swimming in the waters of the Amazon and Orinoco river basins, it might be challenging to determine which one it is - an advantage for this small fish. The Amazon leaffish, Monocirrhus polyacanthus, might seem harmless but is a "wolf in sheep's clothing" or, better yet, a "fish in leaf's clothing". Their remarkably laterally compressed body and orange-yellow to brown colours resemble a floating dead leaf, making it easier to approach unaware prey. The colour patterns' mimicry is outstanding, with several markings that give the impression of dry leaves. But they don't rely only on appearance, putting up a whole show - they actually mimic their environment to facilitate their attack. Amazon leaffish are known to prefer oxbow lakes and streams of blackwater rivers, which are typically dark due to plants' decomposition. Adults live in shallow waters, near fallen leaves on the surface, swimming in a floaty manner towards their prey - fish, crustaceans, and insects. Some scientists say their coloration can adapt to the environment and accentuates during reproductive periods. Sadly, not much more is known about this ludicrous fish. Reproduction has only been observed in aquariums, where it showed an aggressive courtship and male parental care of eggs and larvae, while the female is responsible for driving away intruders. Due to its curious-looking body and rarity, it's exploited by the ornamental fish trade. 

© Jan Harmsky / www.lifeinfreshwater.net


#133 European crayfish

Also known as Noble crayfish, the European crayfish, Astacus astacus, is indigenous and widespread throughout its namesake continent. But it's the only native freshwater crayfish species in Norway and Sweden. It has been traditionally fished and eaten for centuries in the latter country, having considerable cultural, social, and economic value. From large lakes to small streams, it prefers shores and shallow waters, especially where it can hide from predators (e.g., minks, otters, and eels) like steep banks where it digs deep burrows. They are nocturnal and omnivorous. When the water starts to get cold in Autumn, it's mating time. Females carry the fertilised eggs under their back until the following summer when the eggs hatch with tiny crayfish. These younglings can grow up to 18cm and live a long time, likely over 20 years. But some might not make it, as their populations have decreased dramatically locally. This species is Critically Endangered according to the Swedish Artdatabank's National Red List 2020, mainly due to an invasive species - the Signal crayfish. During the 1960s, introductions in Swedish waters aimed to replace the native species affected by crayfish plague. But it was not known that the North American crayfish carried the plague while withstanding the disease. The European crayfish also faces habitat loss and degradation, as their natural river flows are being altered by hydropower dams. But there's still hope. It's listed in the EU's Species and Habitats Directive, which means that Sweden has a national responsibility to manage the stock. WWF's conservation work focuses on their freshwater ecosystems' health. 

© Ola Jennersten / WWF-Sweden


#132 Goliath frog

Meet the world's largest frog – the Goliath frog, Conraua goliath. Also known as Giant slippery frog, it can reach the size of a small cat – up to 34 cm long and over 3kg. Native to a narrow rainforest region of Cameroon and Equatorial Guinea, it lives in or near clean, large, and fast-flowing rivers and streams. This river giant is omnivorous and opportunistic, feeding both submerged or out of the water. Although scientists previously thought it didn't vocalise, it has an interesting repertoire of calls that includes short whistles, chirping, and even a "sighing deep roar". During breeding, they create nests in streams and small rivers by clearing the area of residues and leaf litter. Recently, scientists found that nesting (likely done by males) includes the heavy lifting of rocks up to 2kg – which might explain why this species evolved such a large body. They observed 3 types of nesting sites to protect developing offspring from river torrents and predators: rock pools, existing washouts, and dug-out depressions in gravel riverbanks. Adults guard the nests filled with 150-300 eggs at night, where tadpoles finish their development into frogs. When feeling threatened, they escape by jumping into the water with a single leap, sometimes skittering across the surface with consecutive hops reaching 3.5m. On land, they seem exhausted after a few jumps, making them easy to capture. Listed as Endangered, they face threats like overhunting for food and the pet trade, habitat and sedimentation loss due to agriculture and hydropower dams, and climate change. Conservation efforts should include keeping their rivers healthy and flowing and working with the local communities to manage harvests sustainably.

© Dr. Ken-ichi Onodera / Yuichi Oba / Tomosang


#131 Genji-botaru firefly

Few insects get such a high level of people's attention as fireflies do. And the Genji-botaru firefly, Luciola cruciata, probably like no other in Japan. Of 2000 firefly species worldwide, fewer than ten are aquatic at the larva stage. Distributed throughout Japan's main islands (Honshu, Shikoku, and Kyushu), Genji-botaru's larvae live in clean fast-flowing rivers, streams, and rice paddies, and all its stages - eggs, larvae, and pupae, adult - are luminous. Aquatic fireflies have been very popular in Japan since ancient times, when people lived in a suburb-like environment cultivating paddy rice with water from nearby streams and often saw the tiny bright lights. They believed the fireflies' lights were the dead's souls. This human-fireflies connection is evident in Japanese literature, where they were depicted as essential items; in art, drawn in old woodblock pictures and painted on refined porcelains; and in traditional children's songs, like the "Hotaru Koi" (= Come, fireflies). During summer, a typical evening activity was "Hotaru-gari" (=firefly hunting). Signalling a seasonal change, at its peak, people would take boats to find the best places to see one of the most spectacular events involving luminescent animals to this date – a large number of flying males flashing in synchrony to attract females. Females lay their eggs among the riverbanks' moss, and after they hatch, larvae crawl to the water, where they spend months underwater feeding on freshwater snails. Once young fireflies, they go back to the riverbank and become adults. Slowly and silently, they start shining their light and hover over the river when it's time to court. Sadly, this brilliant species is at risk. Its wild population decreased dramatically in the last ten years due to pollution, habitat loss, and commercial capture. Conservation efforts include Genji-botaru's repopulation activities and the designation of several areas  – especially those where these fireflies swarm - as natural monuments by the Japanese government. 

© Day's Edge Productions WWF-US / Juan Pratginestos WWF


#130 Yellow-spotted river turtle

Native to several South American countries, the Yellow-spotted river turtle, Podocnemis unifilis, is one of the largest freshwater turtles. This species is called charapa or side-necked turtle as it cannot completely insert its head into the shell but bend its neck to one side to attach, leaving a part open. It’s known to inhabit the colossal Amazon River basin, preferring the main channels of large rivers, where it spends most of its time underwater. Yellow-spotted river turtles’ reproductive behaviour is synchronised with seasonal variations in water levels – every year, they congregate for mating and spawning in the dry seasons. To prevent nests from being washed away, they lay their eggs on the dry rivers’ banks and sandy beaches. And hatching mostly coincides with the beginning of the rainy season. They feed on small animals (e.g., crustaceans, insects, molluscs, and fish) and aquatic plants and fruits, being critical seeds disperser. In addition, they have another crucial ecological role as a food source for other animals, including humans. Harvested since pre-colonization times due to its high nutritional value, it is nowadays mainly threatened by unsustainable exploitation, followed by habitat loss and degradation, and climate change. In Ecuador, their populations have declined so severely due to illegal commercialization and overharvesting that they are listed as Critically Endangered. But there is hope - ongoing projects with indigenous communities in the region are looking to restore the Yellow-spotted river turtle populations. Conservation efforts for this and other Amazonian freshwater turtles are likely to be more successful with local community involvement, healthy freshwater habitats, and free-flowing rivers.

© T.Friedrich IHG_BKU


#129 Baltic Sturgeon

The Baltic sturgeon was integral to the region's fauna and culture until the middle of the 20th century. Although it spends most of its long life – up to 150 years – in marine waters, the Baltic sturgeon, like all migratory fish, is vulnerable to diverse habitat impacts because they use rivers, estuaries, bays, and the ocean at various points of their life. Their spawning sites include the Baltic Sea's southern tributaries, like the Oder river, ranging from lower sections to headwaters around 1,000 km from the sea. But they were overfished, their migratory routes blocked by hydropower dams, and their habitats polluted – subsequently, the population disappeared with the last documented sighting in the Baltic Sea in 1996. After several years of debates, genetic investigations have shown that the closest remaining relatives come from the northernmost populations of Acipenser oxyrinchus in North America. These populations support restocking efforts in the Baltic Sea range, and results show increasing numbers of juveniles in coastal waters. Yet, there is still no evidence of returns of mature fish or natural reproductions. The year 2022 marks the 15th anniversary of restocking events in the Oder River, where several million fingerlings have been continuously released in cooperation between Germany and Poland. As the species needs approximately 15 years to mature, hopes are high that we can soon witness their first natural reproduction. However, these efforts will only be truly successful if we tackle why they were extinct in the first place. Fisheries with bottom-set gillnets pose a huge threat to the Baltic sturgeon, which ends up as by-catch. But the most pressing threat comes from the navigation development projects in the Oder river basin. Poland and Czech Republic governments plan to create the E30 Waterway, which would basically turn the river into a channel and destroy river banks or deep holes, which are used by sturgeon to overwinter and reproduce. This infrastructure would also be detrimental to a wide range of aquatic biodiversity and completely alter the Oder. But we can still save the Oder and its wildlife. In addition to restocking, sturgeons' conservation efforts include habitat restoration, raising public awareness and political will to support implementation, advocating for alternative renewable energy sources, and removing old dams

© WWF Austria / Hannes Greber


#128 Ship sturgeon

The Ship sturgeon, Acipenser nudiventris, is extinct in the Danube and thus the entire EU territory, despite being protected under the EU Habitats Directive. A sad event that has, since its adoption in 1992, rarely happened before. On a global level, this species' population declined more than 99% in the past three generations (around 120 years). Nowadays, the only confirmed self-sustaining population results from a translocation out of the native range within Kazakhstan. Like the majority (2/3) of sturgeon species, it is listed as Critically Endangered by the IUCN Red List of Threatened Species, indicating its high risk of extinction. Sturgeon are the world's most threatened group species due to historic overexploitation. They face ongoing poaching for illegal trade in wild caviar and meat, hydropower dams blocking migratory routes, unsustainable sand and gravel mining, and habitat loss. As migratory fish, they are good indicators for connected ecosystems - their disappearance highlights freshwater biodiversity's decline and our rivers' degradation. Ship sturgeons used to swim the Black, Aral, and Caspian Sea basins, including large rivers like the Danube. Although there are pure freshwater forms of ship sturgeons, like many sturgeon species, they spend part of their life in salt water and return to rivers to breed. It could reach 2,2m in length, weigh up to 120kg, and live for more than 30 years. The situation for ship sturgeon is bleak. But there's still hope, especially after scientists found six young ship sturgeon in the Rioni River, where a recent expansion of a sturgeon-protected area could boost conservation efforts. WWF's Sturgeon initiative is also working to restore our rivers' health and give sturgeons a fighting chance.  

© Alastair MacEwan / Silverback/Netflix


#127 Rough-skinned newt

The Rough-skinned newt, Taricha granulosa, is a stocky salamander known for its annual mass migrations and potent toxin. Endemic to the hilly and mountainous forest areas of the USA and Canada Pacific Northwest, this species can be found on land or in ponds, lakes, reservoirs, and slow-moving streams. They migrate to and from these aquatic habitats, where they find a mate and breed (check this fantastic video). After fertilisation, the female deposits the eggs singly from her cloaca on aquatic plants, submerged twigs, and detritus. Rough-skinned newt’s larva preys on small aquatic invertebrates, and some populations develop into gilled adults, but they mostly breathe through lungs and their skin when swimming. Even though it carries a cute-looking face and a small body for humans - up to 22 cm in length - it’s the most toxic newt in North America. Its toxin, known as tetrodotoxin, is harmful to people and responsible for severe illness and even death when ingested – it’s crucial to be careful and avoid touching them. The toxin serves as an antipredator defence, but they are still prey to racoons and especially garter snakes, which evolved resistance to it. Rough-skinned newts also have another strategy: when feeling threatened, they adopt a defensive position – the unken reflex, which likely inspired some Pokémon characters - where they extend their limbs, raise their heads while closing their eyes, and turn up their tail over their body curling the tip. But what really threatens them is human-driven terrestrial and freshwater habitat loss and degradation, and the release of non-native salamanders in their territory. 

© Stefan.lefnaer / H. Zell


#126 Sweet flag

The Sweet flag, Acorus calamus, might not look unique, but it's highly valued across several cultures mainly due to its not­­orious roots. Growing on the margins of shallow nutrient-rich water and streams, canals, fishponds, and lakes, this wetland species is renowned for its long history as a medicinal plant. Mentioned by the father of modern medicine – Hippocrates - it has been used since ancient times as a hallucinogen and an old folk remedy for treating arthritis, diarrhea, hair loss, and other disorders. And there’s more - this semi-aquatic species is multifaceted, used to flavo­­ur pipe tobacco; to purify sewage due to its high tolerance for ammonia and anoxia; in perfumes due to its sweet fragrance, among other. To this day, Sweet flag is studied for its various pharmacological properties, but there are still safety concerns around its toxicity – especially carcinogenicity. Since 1968, this species and its products have been banned as human food or food additive in the USA, and its use is regulated in Europe. Probably due to its versatility – and high pollution tolerance - it became widespread, even generating discussion of its real native range. Most likely native to subtropical Asia, it's non-native throughout much of Europe and southern North America. Although listed as Least Concern by IUCN, there are some local extinctions records. In addition to a growing demand for the drug markets, this species is under threat – like most medicinal plants - from habitat fragmentation, deforestation, and overharvesting. It's time we value our freshwater habitats for all the benefits they safeguard for humans and nature. 

© Jan Harmsky / www.lifeinfreshwater.net


#125 Water stick insect

As it often happens with freshwater species, it’s possible to cross paths with the Water stick insect, Ranatra linearis, without ever knowing. With its weird stick-shaped body, this aquatic insect is commonly mistaken for other objects or its terrestrial look-alike. They also usually go unnoticed by their game – hiding in shallow and densely vegetated bodies of water, they cling parallel to the underside of leaves, waiting for unsuspecting prey to come within reach. Striking with their specialised raptorial front legs, they pierce the captured prey with a tube-like mouthpart and inject them with venom, causing tremors and eventually paralysis. This sit-and-wait ambush predator spends most of its time in water environments waiting for prey, including young fish, insect larvae, small crustaceans, and quite notably, the lesser water boatmen. Compared to other insects, they have long legs, which likely helps them capture the water boatmen, one of the fastest swimming aquatic insects. Belonging to the same family as water scorpions (Nepidae), they also have a long breathing syphon (tube) at the end of their abdomen to pierce the water surface for air, sometimes mistaken for a stinger. Commonly found in fresh or brackish waters of Eurasia and North Africa, this insect of around 35 mm - 50 mm is recorded as the largest animal found in hypersaline water bodies - water at a salinity greater than 24 grams p/L, saltier than ocean water. Although appearing wingless, adults have stiff wings that lean on their backs at rest. Most water bugs are impressive fliers, but not the Water stick insect, which is a bit clumsily. They fly mostly to move to another pond in case their own starts to dry up during the summer months.

© Shutterstock / Pavaphon Supanantananont / WWF


#124 cuckoo catfish

The cuckoo catfish, Synodontis multipunctatus, is endemic to one of Africa's Great Lakes - Lake Tanganyika. This freshwater fish is named after the cuckoo bird due to their shared (in)famous reproductive strategy - brood parasitism -  that includes finding unaware foster parents for their offspring. The cuckoo catfish is a member of a small group of squeaker catfishes (family Mochokidae), but it is the only one to smuggle its eggs into the care of another species - thick-lipped cichlids. These mouthbrooding cichlids lay their eggs in specially prepared nests, and females collect their eggs immediately after spawning to incubate them in their mouths for about three weeks. Cuckoo catfish exploit the cichlid's parental care by invading their nests at spawning time and creating enough chaos to quickly deposit their cuckoo eggs, which are mistakenly scooped up by the unsuspecting female "surrogate". Male cichlids do respond aggressively to the intruding cuckoo groups, but they get overwhelmed by repeated advances. Although the eggs are not similar - catfish's eggs are different in shape and smaller - cichlid females have to act quickly as their own eggs are at risk of being eaten by the invader. Recent studies show that females co-existing with cuckoo catfish may be able to selectively reject its eggs, but how it's still unknown. Having a cuckoo catfish as a stepsibling can be fatal for baby cichlids - catfish eggs hatch earlier, and they devour the cichlid's embryos over several days. This and other astonishing behaviour in our richly biodiverse freshwaters are still mostly unknown – and we might never get to know them if we don't protect these habitats.

© Wild Wonders of Europe  / Christian Ziegler / WWF 


#123 Dice snake

Also known as the Water snake, the Dice snake, Natrix tessellata, holds the title of one of Europe’s most aquatic snakes. Living near rivers, coasts, streams, lakes, ponds, and the surrounding terrestrial habitat, it is adapted to prey underwater. With a preference for fish and frogs, Dice snakes use frontal strikes to capture these prey underwater, assisted by their visual system that allows for better focus when submerged than other similar species. Females of this species are bigger than males, and both are active diurnally and nocturnally. During the hottest months, however, it’s almost entirely nocturnal in southern parts of its range, making it more difficult to spot its sometimes vividly coloured belly in yellow or orange with black spots - very similar to dice, ergo the name. Nonvenomous, this harmless snake has a wide Eurasian distribution, and it is also present in Egypt. Listed as Least Concern by the IUCN Red List of Threatened Species, their populations are decreasing, and there are reports of local extinctions due to habitat deterioration. They are threatened by the loss or modification of wetland habitats caused by, for example, river channelization and lake-shore development.

© David J. Stang



Wattled cranes, Bugeranus carunculatus, are Africa's largest and rarest crane. They once ranged from coastal west of Africa to the African horn down to the southern tip of Africa, but nowadays are mostly concentrated in the Okavango delta. Listed as Vulnerable by the IUCN Red List of Threatened Species, their populations have suffered significant declines in southern Africa over the past few decades, especially due to wetlands degradation. This species is the most wetland-dependent of Africa's crane species - relatively intact wetlands like Cuando represent, therefore, an important refuge for these birds. They feed mainly on tubers and rhizomes of aquatic vegetation and large invertebrates and small vertebrates. Generally, they are also not migratory, but those that inhabit seasonal wetlands are irregularly nomadic in response to water availability. They are often seen in pairs – or trios with young birds – where the male tends to be larger than the female. They are usually silent and territorial when in pairs, but they can be seen in larger "floater" flocks.



#121 Smooth-coated Otter

The Smooth-coated otter, Lutrogale perspicillata, is the largest otter species in Asia. Found in South Asia and Southeast Asia’s slow-flowing waters typical of rice paddies and floodplains, and large rivers in some regions, they have a large distribution that is slowly and steadily decreasing. It was once widespread from the Middle East to southeast Asia, but its biggest asset became a problem – its short, smooth velvety fur is attractive to the illegal wildlife trade. The smooth two-layered fur - warm chocolate brown on the back and soft grey on the stomach - helps keep the underfur dry underwater to retain body heat. Mainly nocturnal, this species forms large, vocal family groups that prey together on fish, shrimps, frogs, crabs, insects, and birds. They catch prey with their sharp claws on their webbed paws, which boost their swimming abilities together with their paddle-like flat tail. Listed as Vulnerable by the IUCN, habitat degradation and loss due to increasing anthropogenic pressure on wetlands and waterways threaten these otters. They need thick riverside vegetation to hide, dig dens and raise cubs. In addition, illegal trapping for the fur trade has recently taken a heavy toll in many of their range countries, and law enforcement is lacking. They are also wanted as pets and for traditional medicine. 

© Threat - Brown trout trying to jump man-made river barrier in Finland


#120 Brown trout

The brown trout, Salmo trutta, is a migratory fish native to the cold rivers and lakes of Europe, spawning in rivers and streams with clean gravel beds. Due to its high value to fisheries, it has been introduced to many rivers globally, sadly becoming an invasive species in some areas like North America. Adults are easily mistaken for the Atlantic salmon, as they have spots under the lateral line while the Atlantic salmon do not. The migrating populations are also called sea trout - they generally feed in freshwater and usually go to the sea after spawning. Females are the ones that select the spawning sites, where they form spawning beds called redd –bowl-shaped indentations of clean, bright rocks - by beating the rocks with their tail-fin to remove moss, dirt, bigger rocks, and debris. The male's role is to guard and defend the females against other males, and after fertilizing the eggs, females over the eggs with gravel. This species is threatened locally by pollution (especially the eggs), impacts from salmon farming (e.g., sea lice), and dams. For example, the Vistula River in Poland had a large sea trout population, which was able to migrate until the Carpathian mountain tributaries, almost 1,000 km from the sea. However, after the dam of Włocławek was constructed in the 60s, sea trout have been observed above the dam only occasionally, disappearing from the upper part of the basin.

© Multiple photographers


#119 Indus valley bullfrog

Indus Valley bullfrog, Holobatrachus tigerinus, a.k.a Indian bullfrog, is one of the largest frogs on the Pakistani plains. Found in the freshwater wetlands - natural and artificial – of Pakistan’s Indus River basin, this frog can hibernate during winter and drought by burrowing itself in soil. It is also common in paddy fields and moist riparian areas of Afghanistan, Bangladesh, Bhutan, India, Myanmar, and Nepal. Sadly, it has been introduced to Madagascar and Maldives, which can have a negative impact on the invaded ecosystem’s integrity. Indus Valley bullfrogs are voracious feeders - anything that is moving is game, bounced upon, and swallowed. If needed, they use their anterior limbs to thrust larger food into their mouth, including mice, young frogs, juvenile snakes, and small birds. They don’t tend to stay in water for long – when danger approaches, they plunge into deep water using their almost fully webbed feet and stay underwater for a few minutes. If in clear pools,they hide under bottom gravel. With the beginning of the monsoon, a large number may be seen all over the fields around temporary water pools. And many of them will be easier to spot due to their recently acquired lemon-yellow colour. Yes, this species can change colours – during the breeding season, males turn yellow and their deep blue vocal sacs more prominent, while females remain dull and drab-coloured. Sitting close to each other in shallow water, calling males repeat their powerful nasal call several times, now and then jumping over each other. Lurching around, females are grabbed by the males when in range, and after some fighting with the neighbours, the pair somehow moves to a quieter place to lay the eggs. This species is listed as  Least Concern by IUCN Red List. 

© Jim Capaldi


#118 Ocellate river stingray

The Ocellate river stingray, Potamotrygon motoro, is the most abundant and widespread river stingray species across South America, occurring in the rivers of the magnificent basins of Uruguay, Paraná-Paraguay, Orinoco, and Amazon. Like many river rays, it prefers calm waters, especially sandy margins. Although most commonly seen when water levels are low, this species is found in both shallow- and deep- waters, as well as clear and murky. Generally, they are found still and hiding, partly burying themselves, especially during the warmest period of the day. When seen in shallow water, artisanal and commercial fishers catch them mainly for their meat. But due to their attractive patterns of dark-ringed orange spots, they are also collected for the ornamental fish trade, especially juveniles. But mishandling this species might come with a painful, but not deadly, price – their tail has a venomous sting, which they use to protect themselves when feeling threatened or when unaware bystanders step on them. According to scientists, this curious species can also discriminate colours and process numerical information. And females usually give birth to an odd-sized offspring, varying from 3-21. Even though they are listed as Data Deficient, their freshwaters, especially the River Paraná, are at risk of habitat degradation caused by damming, navigation, hydroelectric plants, and the construction of many ports along the river.­­

© Jozef Grego


#116 Dalma Snail

The Dalma snail, Hauffenia kissdalmae, is a member of the most species-rich freshwater snail family, Hydrobiidae (spring snails). This family encompasses tiny creatures, mostly living in very clean and well-oxygenated waters, springs, small streams, cave streams. Many are narrow-range endemic species,  occurring within the drainage of one single streamlet or even in one single spring or cave. That might be the case of the Dalma snail, discovered in a small spring in the Börzsöny Mts, in Hungary in 2008. This species inhabits the' shallow subterranean habitat' - fissures and cavities in the bedrock close to the surface. In 2011, it was listed as Data Deficient by IUCN because its exact distribution and population numbers were unknown. Since then, intensive research revealed about 40-50 populations in the Slovak and Hungarian part of the Northern Carpathians, distributed over an area of around  800 km2. Although one might think that its underground lifestyle would guarantee them safety, a recent study suggests otherwise. Feeding on bacteria living in the delicate net of tree rootlets, their survival depends heavily on the constant forest cover and the presence of old trees. The fate of a Slovak population monitored between 2012 and 2021 illustrates their vulnerability - in 2014, deforestation occurred in this population's spring vicinity. After that, fewer and fewer live specimens were found until they disappeared entirely after a few years. This case highlights the complex relationships and interactions between organisms within an ecosystem and how little we know about them. And in particular, how easy it is to destroy these fragile systems.

© Martin Harvey / WWF


#117 Waterbuck

The waterbuck, Kobus ellipsiprymnus, is a highly water-dependent mammal. It is usually only found “at or near water” due to its high susceptibility to dehydration and overheating relative to other African bovids. This medium-sized (150–300 kg) antelope occurs widely throughout Africa, in habitats like lakeshores, riverine woodlands, and open grasslands, including the dazzling Hluhluwe-Imfolozi Park in South Africa, where the life-giving Imfolozi River boasts rich biodiversity. Waterbucks have a reputation of being smelly due to a musky oil secreted by glands in their skin, which forms a waterproof layer around the hair, protecting their skin when they enter the water. They have been known to dash into water to evade predators like lions and leopards. They also exhibit strong territorial behavior, where males defend areas close to water with abundant and high-quality forage. Although listed as Least Concern by the IUCN Red List, this species’ populations are declining due to hunting. 

© Shutterstock / Agami Photo Agency / WWF


#114 Hooded Grebe

The Hooded Grebe, Podiceps gallardoi, moves like no other bird. With the South American lakes as their stage, they perform an unusual courtship dance sometimes referred to as "Tango in the Wind". The dancing ritual combines rigorous headbanging displays, occasional diving, and some intense stare-downs, and the suitor with more rhythm, stamina, and coordination tends to be the fitter partner. Striking also in appearance, this exquisite bird is unique on many fronts – it's a rare endemic species, with the only known wintering grounds located at the estuaries of Río Coyle, Río Gallegos, and Río Chico on the Atlantic coast of Santa Cruz, in Argentina. The breeding season arrives with springtime, when they migrate to the Patagonian steppe to set up nesting colonies on a few interior lakes. Very few people reach this region, so these aquatic birds were found only a little over 40 years ago. But, sadly, they are already Critically Endangered. Nowadays, just 750 breeding adults are left – an 80% plummet since the 1980s. The lakes suitable for their breeding are reducing at an uncommonly fast pace due to climate change, which also aids and bolsters the impact of three invasive species – a fish, a bird, and a mammal. The Rainbow trout, Oncorhynchus mykiss, changes the entire food chain, devouring the same freshwater invertebrates that these grebes usually feed on and likely preventing the growth of the only aquatic plant in these lakes, essential to building the grebes’ floating nests. The Kelp Gull, Larus dominicanus, recently arrived at the highland plateaus, preying on colonies during a critical moment of their life cycle - the egg-laying phase. The most devastating effect comes from the predation by the American Mink, Neovison vison. But it's still possible to prevent the extinction of this unique dancer. Urgent conservation action is underway via initiatives such as the Hooded Grebe Project. 

© WWF / François Xavier Pelletier


#115 Ganges river dolphin

The Ganges river dolphin, Platanista gangetica gangetica, is one of the most ancient dolphin species still alive, being considered a living fossil. It is known as the "Tiger of the Ganges" due to its role as a top predator and an ecosystem indicator species – like a tiger is in its habitat. This species has many common names, which in local languages are reminiscent of the dolphin's breathing noise like "susu". But they are generally shy towards humans and most often found alone. With extremely poor eyesight, they rely almost entirely on echolocation to navigate and locate their prey, usually fish and crustaceans. They are found only in the river systems of the Ganges-Brahmaputra-Meghna, and nearby Karnaphuli-Sangu River, in Bangladesh, India, and Nepal. Like the Indus river dolphins, they have a particular side swimming behaviour that helps them navigate shallow waters. In the past, during the monsoon season, these dolphins would move upstream into smaller rivers and then back downstream to larger channels in the low water winter. But nowadays, dams and barrages restrict their movement. They are under great threat due to proposed and ongoing large infrastructure projects, which can also destroy their habitat and decline river flows. Listed as Endangered by the IUCN Red List of Threatened Species, they are also at risk because of fisheries bycatch and pollution. But there's hope for the Ganges river dolphin. They are legally protected in all the countries in which it lives. And WWF's initiatives like River Dolphin Rivers tackles the systemic threats – unsustainable fisheries, hydropower and infrastructure, and pollution –, also protecting their habitats for the benefit of people and nature (Learn more about this species with this video). 

© Averroes Oktaliza


#113 New Guinea Crocodile

The New Guinea crocodile, Crocodylus novaeguineae, is a medium-sized crocodile that prefers swimming in New Guinea island's vast freshwater systems like rivers, swamps, and marshes. Restricted to the island of Papua New Guinea and Papua including  Pulau Kimaam , this species can grow up to 3 m for females and 3.5 m for males, especially in the Sepik River, where larger animals can be found. The Sepik is one of the largest rivers in the Asia-Pacific region, harbouring some of the world's largest freshwater and saltwater crocodile populations. Sepik's crocodile species, including the New Guinea crocodile, have cultural significance to the communities living across the river - they pay them tribute every year with a three-day Crocodile Festival. Inspiring cultural traditions, beliefs, and legends, this ancient animal symbolises strength, power, and manhood. Man and crocodile share a special bond in Sepik culture, literally embodied by men proudly wearing scars that resemble the back of a crocodile. It's during the rite of passage of skin-cutting initiations that they cut these scars into their skin from shoulder to hip. Listed as Least Concern by the IUCN, this species' populations benefit from the vast areas of wetland habitats and low human population density in Papua New Guinea and Papua. Management programs regulate exploitation while providing equitable economic incentives to indigenous landowners. There are threats from introduced fish (Pacu, Piaractus brachtpomus) and mining which could increase in future. Plans to develop the largest mines in the country on one of Sepik's major tributaries threaten the future of the river basin, its people, and nature. But the people of the Sepik are fighting to save their river and all it offers them.

© Benny Trapp CC BY-SA 3.0


#112 Fire-bellied toad

The Fire-bellied toad, Bombina bombina, it's known for its namesake black and red-orangish markings on the belly and its melancholic call. Found in Central and Eastern Europe, this toad prefers living in stillwaters including lakes, ponds, swamps, peat bogs, ditches, flooded rice fields, and quarries. When faced with potential predators, Fire-bellied toads have curious reactions like the defensive posture called the "unkenreflex" – they turn over and curve their bright belly upward, covering the eyes with their palms. Or, instead of turning over, it bends its body downward, lifts up the head, and curves the extremities showing the bright spots on its flanks and the extremities' ventral surface. This behaviour adds to its survival strategy - even though it has venomous skin secretions, many vertebrates regularly consume these toads. Staying mainly in the water or near the shore, during winter they hibernate in the mud on the bottom of water bodies or land. When the breeding season starts, males vocalize floating on the water surface, with their bodies flattened, and sometimes they can call from under the water. For breeding, they prefer shallow ponds as these warm up quickly and have plenty of submerged aquatic vegetation. They stay in ponds after breeding, but these ponds can dry up in late summer. This species is rapidly declining in Germany because these ponds are currently disappearing - in Lower Saxony, it is now only present in the Elbe Floodplain. Although listed as Least Concern by IUCN, the Fire-bellied toad is significantly declining or extinct in many areas, especially West Europe. The most serious threat is wetlands' destruction. 

© Manfred Schartl


#110 Amazon Molly

Contrary to what its name might suggest, the Amazon molly, Poecilia Formosa, does not live in the Amazon River basin. Rather, it swims the waters of the Rio Grande/Bravo lower basin and Tuxpan and Nueces rivers. The reason for its name is because it consists almost entirely of females – like the Amazons, a tribe of warrior women from Greek mythology. This inconspicuous fish is one of the few asexual vertebrates in the world, having originated by hybridization. They reproduce via gynogenesis – they simply clone themselves, not producing any male offspring. But unlike other asexual organisms, Amazon mollies still need help to reproduce – they mate with closely related Molly fish, from which they obtain sperm that will trigger the cloning process. However, none of the male’s genes is incorporated into the offspring’s DNA – instead, it is completely destroyed. Researchers from the Universität Würzburg studied how the Amazon molly still exists, as according to established theories, it should have been extinct during the course of evolution. Their central insight was that this species has a unique genetic variability, especially high for relevant genes of the immune system, and clear signs of an ongoing evolutionary process. This rare vertebrate is listed as Least Concern by IUCN, being represented by many subpopulations and locations. But the population trend is unknown and its clear and muddy freshwater habitats, like the Rio Grande/Bravo River, are under pressure from climate change, dams infrastructure, irrigation, among other threats. 

© Shutterstock / Carlos Aguilera / WWF 


#111 Zambezi shark

The Zambezi shark, Carcharhinus leucas, a.k.a. bull shark, is one of the few shark species known to travel long distances into rivers systems and remain there for long periods. Famous for this ability, it's also named after the mighty Zambezi, where it reached up to 1120km away from the ocean. But they also swim other rivers – and even hypersaline lakes - worldwide, with a record of 5080km away from the ocean in the Amazon/Ucayali River. But why and how do they do that? They rely on estuaries and rivers as nursery habitats, where pregnant females give birth and juveniles can remain for five years. They are a fully euryhaline species, able to move easily between marine and freshwater habitats thanks to osmoregulation - their body acclimates to changes in salinity via independent regulation of sodium/chloride and urea levels. This adaptation favours their broad range, including coastlines of all three big oceans (Atlantic, Indian, Pacific) in both hemispheres, with evidence of their presence in 415 fresh and brackish water localities. Reaching up to 4m in length, they are named Bull sharks due to their short, blunt snout and tendency to head-butt their prey before attacking. They are generalist predators  and eat almost anything they see - fish, including other sharks, and also dolphins, birds, turtles and invertebrates. This species is listed as Vulnerable by the IUCN due to fishing as a target for meat and fins and a bycatch. In addition, their habitat preference means they are also threatened, especially juveniles, by habitat loss and degradation, including damming, pollution, and climate change. In the Zambezi River, the Cabora Bassa Dam wall and the Kariba Dam currently prevent this species' migration to the river's upper reaches. 

© Gerald Kuchling


#109 Yangtze Giant softshell turtle

The Yangtze Giant softshell turtle, Rafetus swinhoei, is one of the world’s rarest reptiles. Reaching around 120 kg in size, this enormous freshwater turtle is a bit strange-looking with its long flat carapace, soft body, pig nose, and a long neck capable of “periscoping” like an otter. Due to its rarity, we know very little about them - adults seem to be omnivorous, fairly sedentary and reach up to 100 years. They are worshipped in some areas - Vietnamese mythology says this enormous turtle is the living representative of the Great Turtle God, Kim Qui. But not even its god-like status could save them - they are one of the most severely threatened species on Earth. Listed as Critically Endangered, only four surviving individuals are known - two of which are in captivity, and none have reproduced successfully recently. Decades of dam-building likely fragmented populations, getting several turtles stranded in lakes and reservoirs. This species is also at the brink of extinction due to exploitation of adults and eggs for (subsistence) consumption and targeted capture attempts in recent years, habitat loss for agriculture like rice paddies, pollution of wetlands and riparian habitats, and sand mining. Historically, this species inhabited the Red River of Yunnan and Viet Nam and the lower Yangtze River floodplain. Nowadays, its area of occupancy is less than 10km2 after a population reduction of over 99% over the last two generations. But we can’t give up on these divine turtles. Captive breeding efforts continue, and field surveys to locate additional animals in the wild. The Asian Turtle Program works with villagers and stakeholders to protect and monitor the two known wild individuals in Viet Nam. And WWF’s Emergency Recovery Plan outlines how to reverse the rapid decline of their critical freshwater habitats. 

© Joel Deluxe


#108 Rio Grande silvery minnow

The Rio Grande silvery minnow, Hybognathus amarus, is one of the most Endangered fish species of North America. It was once widespread and abundant, swimming the river basins of Rio Pecos and Rio Grande/Bravo in Texas, New Mexico, and Mexico. Nowadays, it is only seen in a 280km stretch in New Mexico - from Cochiti Dam to the headwaters of Elephant Butte Reservoir. Even though they prefer the basin’s low-flow and perennial streams and rivers, they reproduce when there is higher flow. Pursuing a single female, the male nudges the female’s abdominal region and wraps himself around her when she is ready to spawn. They spawn together, with males presenting several spawning episodes with 10 minutes intervals. Thousands of semi-buoyant, non-adhesive eggs, will then passively drift downstream while developing. But all this strategy might not pay-off if the river they rely on continues to run dry due to frequent droughts such as have occured in recent decades. Their populations have already declined greatly due to the historical demand on the waters of the Rio Grande/Bravo for agricultural activities, which led to habitat destruction and modification for water allocation and dams, fragmenting their populations. This species also faces competition and predation by non-native species, and is also at risk from pollution. Although some of these have been reduced since the Rio Grande Silvery Minnow was listed as Endangered, none have been eliminated. Coupled to climate change, this species that depends on side channels and overbanking flows during flooding is being pushed to the brink of extinction. 

© Koen van Uitert


#107 Siamese tiger perch

The dazzling stripes of the Siamese tiger perch, Datnioides pulcher, used to brighten up the rivers of the Indo-China area, from the Mae Klong and Chao Phraya basins to the middle and lower reaches of the mighty Mekong. Extirpated from Thailand in the 1990s, this Critically Endangered fish is now rare in Cambodia, Vietnam, and Lao PDR. The attractive vertical yellow and black patterns are the main reason for its demise - researchers estimate that its global population has declined by more than 90% over the past 20 years after high levels of exploitation for the international aquarium trade. Although rarely seen, it is still fished for this purpose when found. In addition to overfishing, the Siamese tiger perch faces major threats from habitat destruction and degradation from dams and infrastructure in tributaries (small dams, weirs, locks), blocking paths between the main river and tributaries. And this tiger perch does like to swim these waterways, including larger lakes connected to rivers, preferring habitats with submerged woods and rocky crevices. Growing up to 40cm, this tiger perch feeds on fishes and shrimps and was once a popular food fish in Thailand and Cambodia. Artificial breeding has been attempted since the 1990s in Thailand to try bending the curve of its populations, but without success. The species is also protected – it is illegal to catch or possess it. But this law is written under its previous scientific name (Coius pulcher), creating issues when implementing it. And there are many other species on the brink of extinction, and many we don't even know exist. The Mekong River Basin is home to astonishing biodiversity, and hundreds of new species are still discovered every year – WWF's report shows over 200 species identified in the Greater Mekong area just in 2020. The Siamese tiger perch is just one of 95 fishes. The Asian Species Action Partnership (ASAP!) , which is a platform with over 200 organizations including WWF, aims to end species extinction in Southeast Asia.

© Oussama Abaouss/WWF NA-Morocco


#106 Ruddy shelduck

The striking Ruddy shelduck, Tadorna Ferruginea, is a gooselike duck - when in flight, they can look as heavy as a goose. But they are also good swimmers, living around freshwater bodies like wetlands, rivers, and marshes from the Mediterranean basin to Asia. They are mainly nocturnal and omnivorous - their diet includes seeds, grasses, aquatic plants and invertebrates. This species is more than just a pretty orange-brown plumage – it's also quite tough, resisting extremely cold temperatures and rigid climates. Nowadays, they are becoming rarer in southeast Europe, but Ruddy Shelducks are still common across much of its Asian range. Breeding in southeast Europe and Central Asia, most populations migrate to South Asia during winter. Resident and sedentary populations are rare, but some small ones are in northwest Africa, like in the Sebou River basin and Ethiopia. Their movements are linked to the availability of suitable water (moving away from drought-affected areas or to temporary wetlands). Usually, they are in pairs or small groups along rivers. When it's time to breed, a couple forms a close bond, and you can spot the male due to a temporary black ring at the bottom of its neck. After breeding, they cannot fly for a month – adults undergo shedding and regrowing feathers called moulting. During winter and moulting, we might see them congregating into larger flocks, making it even easier to hear them from big distances – they have a particularly loud honking-like call. Although listed as Least Concern, their breeding grounds and stop-over wetlands are being rapidly drained and filled for urban, industrial, and agricultural uses. WWF's Asian Flyways initiative works to protect these pathways and the many marvellous migratory birds that visit them. 

© Michel Gunther / WWF


#105 Yacare caiman

The Caiman yacare is an iconic freshwater reptile of South America. They swim the freshwater rivers and wetlands of Paraguay, Northern Argentina, Southern Brazil and Bolivia, being especially well-known in the world’s largest tropical wetland - the Pantanal. They are even named after their mesmerizing habitat in Brazil, being called “Jacaré-do-pantanal” (Pantanal’s yacare). And they also go by a curious nickname, “Jacaré-piranha” (Yacare-piranha), since even with their mouth closed, they show many teeth. They feed mainly on fish and aquatic invertebrates, but their diet also includes birds, reptiles, and mammals. When fishing, this species  uses a tactic similar to other caimans called collective fishing, where 2 to 15 animals line up in a channel against the current and grab passing fish without individual aggression. It is a medium-sized crocodilian, with male Yacares reaching up to 3m in length and females 2,5m. The mound-nester females place the nests close to canals and rivers, guarding them – behaviour apparently influenced by human hunting pressure – and defending their offspring aggressively when juveniles hatch. Even though abundant, widely distributed, and listed as Least Concern, this species is subject to ranching wild harvest, and its habitat faces many threats. The river that feeds the Pantanal, the Paraguay River, is threatened by hydropower plants. The region also faces agriculture expansion, engineering work for navigation, and climate change. 

© Chernyak Alexey / WWF-Russia


#104 Dwarf sturgeon

The endemic Dwarf sturgeon, Pseudoscaphirhynchus hermanni, is also known as the small Amu Darya shovelnose sturgeon. As its namesake hints, this is a small, rare sturgeon only present in the muddy waters of the Amu Darya River in Central Asia. The enigmatic Dwarf sturgeon is identifiable by its lack of a caudal filament and spines on the snout, a shovel-shaped snout, pectoral fins with a fold that curls dorsally, and of course, its small size. It is poorly studied due to its rarity – its spawning grounds are uncertain, and its generation length is estimated to be from 3 to 8 years due to its smaller size than similar species. The available data shows that Dwarf sturgeon populations are declining, as their range has declined drastically in the past 30 years. The Aral Sea's ecological disaster - which included its drying due to massive water allocation for irrigation, pesticide pollution, and habitat degradation - extirpated this species from the area and the lower Amu Darya. Since then, the Amu Darya River basin has faced habitat alterations from water abstraction, pollution, damming, and channel management, threatening the river's health and biodiversity. Also threatened by poaching, the IUCN Red List of Threatened Species lists the Dwarf sturgeon as Critically Endangered. It was last caught in 1996 in the middle reaches of the Amu Darya, and the last records from the lower reaches are from 1982. However, there is still hope for this rare sturgeon – there are currently unconfirmed fishers’ (poachers) reports catching them, and a study from 2020 confirms they are still there. Part of the species' range is within a nature reserve (Amu Darya Nature Reserve), and WWF's conservation efforts include the Sturgeon initiative and WWF-Russia's on-the-ground work on sustainable fisheries. 

© Martin Harvey / WWF 


#103 Red lechwe

The Red lechwe, Kobus leche leche, is a mammal associated with wetlands, preferring the shallow water margins of floodplains and swamps and occasionally swimming across deep-water areas. It is the most widespread subspecies of the Southern Lechwe (Kobus leche) - commonly seen grazing the wetlands of south-central Africa, including in the magnificent Okavango Delta in Botswana and the Linyanti swamps of the Caprivi Strip, Namibia. Southern Lechwes are medium-sized antelopes that have adapted to their wet environment by having distinctly elongated hooves. Red lechwes feed on the lush green aquatic and semi-aquatic grasses, being particularly dependent on this environment and, therefore, an important indicator species. Lechwes' males (a.k.a. rams) are the only ones to carry lyrate-shaped horns. They are territorial, and males that fail to establish territories congregate in bachelor herds. Females (a.k.a ewes) form breeding herds with their offspring, moving freely between ram territories – males compete for mating favours only when receptive ewes are within their domains. Breeding is not strictly seasonal, especially not amongst Red Lechwe's Botswana populations. When about to give birth to single lambs, pregnant females leave the herd to find cover on clumps of bushes, where they keep their offspring hidden for two to three weeks. Sadly, due to poaching, expansion of agriculture and livestock grazing, changes in water management regimes, drought, and encroachment by alien plant species, The IUCN lists the Southern Lechwe as Near-Threatened, and there is also evidence of Red Lechwe populations' decline over the past years.

© Christoph Walder / ecotone


#102 European grayling

The European grayling, Thymallus thymallus, is part of the salmon family. But unlike many salmonids, this species is generally potadromous, meaning they migrate only within freshwater. European graylings swim in Europe’s submontane rivers with a hard sand or stone bottom and well oxygenated, cold, and fast-flowing water. They are an indicator species for the ecological integrity of the whole river region. They spawn in shallow stretches or riffles, where males defend their small territories until spawning starts. The IUCN Lists this species as Least Concern, but the last assessment was in 2011, while recent studies show that grayling stocks have declined in the previous decades. They are becoming increasingly vulnerable to climate change and under regional threats such as pollution, and dams and river regulation infrastructure. In the European Alps, 80% of all larger rivers are affected by diverse hydromorphological impacts. And there are plans for more infrastructure in the region, like in the Isel river. Instream connectivity plays a fundamental role for many fish species, including this medium-distance migratory species that requires an open river corridor for spawning migrations and movements between habitats. Even though some infrastructure has a fish passage, not all fish can use them. Most importantly, dams and reservoirs alter the natural flow of water and sediment,  affecting this species that is an indicator of river health and an entire ecosystem downstream. 

© Omacha Foundation Fernando Trujillo



Tucuxi, Sotalia fluviatilis, is the guardian of the river and a symbol of good luck, according to the local communities of the Amazon River basin, including the Tapajós river. This positive image is thanks to its ability to avoid rocky and shallow waters, guiding boats to safe river sections. The Tucuxi swims in Brazil, Colombia, Ecuador, and Peru. This species overlaps in range with the Amazon river dolphin, but it is easy to distinguish them, as it is smaller, tends to be in larger groups, and swims faster. This is the only river dolphin that jumps like marine dolphins, and it is perceived as vivacious and sociable. They rely heavily on echolocation to communicate, navigate, and find food in the dark and sometimes turbid waters like other dolphin species. Scientists believe that they prey on various fish species and crustaceans, but studies are scarce. Sadly, they are listed as Endangered due to death caused by fishing gear, habitat degradation due to dams, pollution from gold mining, navigation, and sand and gravel mining. WWF’s River Dolphin Rivers initiative focuses on eliminating the use of gillnets – curtains of fishing nets that hang in the water – and preventing new dams to stop their population decline and enable them to recover. The Tucuxi is also included in international legislation such as the Convention on Migratory Species (CMS). Recently, conservation action plans were put in place for the species at both national and continent-wide levels. Learn more about this river dolphin here.

© Ryan Francis


#100 New Hairy crayfish

The New Hairy crayfish, Euastacus neohirsutus, is endemic to the small and cool creeks fringed by Australia’s rainforest in New South Wales. They are considered widespread within their relatively small range, which includes the Orara and Nymboida Rivers systems. The New Hairy crayfish is part of the Euastacus genus, recognizable by short, robust spikes on its claws, carapace, and abdomen. They are opportunistic omnivores, eating both plant and animal matter, and are rather aggressive and territorial. Their lifespan starts with a relatively long attachment to their mother - after breeding in response to environmental triggers, like a drop in water temperature and stream levels, the eggs remain attached to the mother for 5-6 months until they hatch. It’s only when the newly hatched young shed their outer layer that they lose the connection with their mother. They are slow “growers”, with females taking 7-9 years to reach sexual maturity. The New Hairy crayfish breeds once a year around June, releasing the juveniles around December. IUCN estimated that 82% of Euastacus species were threatened in 2010. The New Hairy crayfish is listed as Least Concern, but it presents fragmented populations. Euastacus crayfish rely on streams for survival, but these are under pressure from habitat destruction, pollution and reduced water quality, the introduction of exotic species, and illegal collection by humans. 

© Rafe Brown


#99 Malatgan River Caecilian

The Malatgan River Caecilian, Ichthyophis weberi, was a “lost” species up to 2015. It was not seen for about 60 years until researchers found one near the Malatgan River in Palawan, Philippines. Caecilians are part of a group of legless amphibians, most species spending the best part of their lives below ground or plying the waters of shallow streams. Malatgan River Caecilians are no different – they live in riverine habitats, usually river banks in lowland forest and adults are likely to be subterranean. Unsurprisingly, much remains unknown about this species, including its breeding strategy and the low number of recordings, which may be explained by its natural rarity or secretive ground-digging behavior. The IUCN Red List of Threatened Species lists them as Endangered due to habitat destruction, especially lowland forests, which results in the degradation of streams and creeks. But there are reasons to be optimistic thanks to the efforts of Fins and Leaves, the NGO that led the expedition for the rediscovery of Malatgan River Caecilians. They also led the work to declare the Cleopatra’s Needle Mountain Range, where this species is found, as a protected area.


© Greg Armfield / WWF


#98 Saddle-bill stork

The striking Saddle-bill stork, Ephippiorhynchus senegalensis, is a widely distributed wading bird in the African continent. This remarkable species lives at large undisturbed wetlands and rivers, generally found near water bodies so it can forage for its favorite fish prey (and eventually crabs, frogs, birds, and insects) with its unique red, yellow and black bill. Growing up to 150 cm in height, it is one of the tallest storks in the world. Saddle-bill storks are mostly resident, with no evidence of regular long-distance migration. Females and males generally nest in solitary pairs and remain that way when not breeding. The easiest way to tell them apart is through their eyes - females have yellow eyes while males are dark-brown. Even though they are listed as Least Concern by the IUCN Red List of Threatened Species, their populations are decreasing due to wetland degradation (e.g., pesticide contamination) and conversion to agriculture.

© Belowwater.com / Oliver Lucanus


#97 Chindongo demasoni

The colourful Chindongo demasoni is a small fish endemic to Lake Malawi in Tanzania. This eight centimetres cichlid occurs at the lake’s small reefs, with a population also thought to be small. IUCN assesses their population as Vulnerable due to threats from sedimentation and over-collection for the ornamental trade. The striking fish inhabits intermediate, stony and rocky substrates in shallow waters, feeding on a mixture of algae, cyanobacteria, heterotrophic microbes, and detritus. Unlike many Malawian fish species males and females have the same colour: a bright light blue body with dark blue/purple to almost black vertical stripes. They differ slightly in terms of length, where the male is a bit bigger than the female. Like most Malawian cichlids, they are mouthbrooders – females will keep the fertilized eggs inside their mouth for about 21 days until their fry is ready for the world.

© Jan Hamrsky



The tadpole shrimp, Triops longicaudatus, is a widely distributed living fossil. Although not really a shrimp, this species is part of a diverse and small group of ecologically important, largely freshwater primitive crustaceans. The broad shield-like double carapace covers most of their body, and when they swim, they present a unique outlook due to the arrangement and the movement of little “limbs” called phyllopods. These phyllopods beat sequentially and fast, forming spectacular wave-fronts. They also use phyllopods to feed, which moves the prey towards their mouth. They live on the bottom of temporary pools, ponds, and shallow lakes, feeding on all available food sources - living or dead organisms – to reach maturity and lay their eggs as soon as possible. Their eggs might be one of the reasons why the tadpole shrimp has been around for so long – they are almost impossible to kill and are even able to survive for decades. If environmental conditions are not favourable (e.g., extreme temperatures), the female will modify the fertilized eggs or “cysts/resting eggs'' to enter a state of dormancy, and they will only hatch once conditions improve. Due to the reduction in the number and quality of temporary wetlands, several species of tadpoles have been assessed as endangered by IUCN Red List of Species

© François Xavier Pelletier / WWF


#94 indus river dolphin

On world river dolphins’ day, meet the Indus river dolphin, Platanista gangetica minor. Endemic to the naturally murky and silt-laden Indus river basin, this species is considered a living fossil together with the Ganges river dolphin, as they are the most ancient dolphin species still alive. Indus river dolphins are functionally blind, relying on echolocation clicks to navigate and find food like other dolphin species. But they emit sound almost constantly, which reflects the complexity of the river environment. As an adaptation to navigate through shallow waters, they developed a unique side swimming behaviour. They are not easy to spot – not only they are generally shy towards humans, but they also surface for only about 1 second before diving back for just over a minute. And, unlike other river dolphins, their dorsal fin is rather small and more like a triangular hump. In addition, this species is mainly solitary, even though it has occasionally been seen in groups consisting of as many as 30 individuals. Listed as Endangered by IUCN Red List of Threatened Species, the last 2000 individuals are mostly found in the lower parts of the Indus River in Pakistan. Their range has been reduced by around 80% due to the construction of irrigation barrages. They are also threatened by dams, entanglement in fishing nets, and pollution. These top-predators are indicators of the health of rivers which are the support system of economies and hundreds of millions of people. And that’s what initiatives like River Dolphin Rivers are trying to protect (check here one of the ways you can support the initiative). 

© Karine Aigner/WWF-US


#96 Water hyacinth

The Water Hyacinth, Eichhornia crassipes, is a South American species with beautiful purple and violet flowers. It grows in shallow temporary ponds, wetlands, marshes, and flowing waters, lakes, and rivers. In its native range, this free-flowing aquatic macrophyte has an important ecological role by providing food and refuge for many species, including waterfowl and waterbirds. It also determines the community composition of other plants, small aquatic microorganisms (including insect larvae and crustaceans), fish and other animals in its freshwater ecosystem. Even though it presents frost sensitivity, it generally tolerates extreme environments (e.g., nutrient supply, temperature), even growing in toxic water. Due to their striking flowers, they have been introduced in many parts of the world as ornamental plants. First records of the species date back to 1816 in Brazil, and its introduction to North America in the late 1800s. Sadly, they are currently known to cause significant ecological and socio‐economic effects and are described as invasive species when established outside their native range. They reproduce quickly, commonly forming dense, interlocking mats and their growth rate is facilitated by water bodies enriched by nutrients from agriculture and waste water – i.e., unhealthy freshwater ecosystems. Once established, the Water hyacinth is not easily removed as standard management and control strategies are costly and not entirely successful. WWF works with partners and local communities to find innovative solutions that are ecologically and socio-economically viable, besides creating awareness on the high risks of humans introducing species to habitats outside their native range. The Emergency Recovery Plan for Freshwater Biodiversity states that a key action is to prevent and control non-native species invasions. Although water hyacinth is problematic when introduced outside its native range, I think we can all appreciate its beauty and importance to its native ecosystem.

© Dr. Lindsey Swierk


#93 Aquatic anole

This lizard is one of the most notable species in the animal kingdom, as it has mastered the art of “scuba-diving”. The Aquatic anole, Anolis aquaticus, is part of a remarkable group of lizards – the Anoles (genus Anolis), which have diversified in many ways to take advantage of their environment. Found along stream margins in the lowlands and premontane slopes of Costa Rica and Panama, Anolis aquaticus is a mid-sized semi-aquatic lizard recently made famous for spending up to 16 minutes underwater! Researcher Dr. Lindsey Swierk hypothesized that they adapted to evade predators by using a bubble attached to their snouts to recycle oxygen – like a scuba tank. Many other lizard species are known to escape from threats via water: some swim, either remaining at the surface or diving, while others use foot-slapping to run over water, and some even combine the two. Aquatic anoles use a combination of surface swimming and diving, jumping into (generally) small and slow-moving streams from the banks and boulders of their riparian habitats to which they are restricted. They swim for a short distance (up to a few meters) or are carried downstream by the current while “rebreathing” exhaled air that gets trapped between their skin and the surrounding water. 

© Jan Hamrsky


#92 Brown China-mark

Most of the lepidopterans (butterflies and moths) with a life cycle associated with aquatic habitats belong to the family of crambid snout moths. The Brown China-mark moth, Elophila nymphaeata, is part of this family - its larvae (a.k.a. caterpillars) are entirely aquatic and have developed various strategies and adaptations to stay underwater. Found in Europe and across the Palearctic to the Russian Far East and China, the adults live for just a few days and can be seen flying from June to September. Generally, they begin flying in the evening, lurking amongst the waterside vegetation during the day. Females crawl underwater and cling to water plants to lay their eggs on the lower side of floating leaves. When they hatch their eggs, the caterpillars start feeding on the leaves. Curiously, this species’ caterpillar constructs a flattened case around itself by spinning two oval pieces of leaves together. This case camouflages and protects the caterpillars, in addition to working as an oxygen reservoir as it’s filled with air and completely surrounds their bodies. They can either carry the case free with themselves or adhere it to their food-plant temporarily. Before becoming full adult beautiful moths, they have to through pupation, where they will spin cocoons of leaf pieces attached to the plant close to the water surface. The pupa connects to the air-filled intercellular cavities of the plant, from where it takes up oxygen. After quietly transforming themselves in 2-3 weeks, the adults fly into the last days of their lives to complete their life cycle.

© MoE / FA / WWF Cambodia


#90 Siamese crocodile

The Siamese crocodile, Crocodylus siamensis, is an extremely rare freshwater species. It was once reasonably abundant in Southeast Asia, inhabiting freshwater swamps and slow-moving rivers of Thailand, parts of Vietnam, Cambodia, Lao PDR, and parts of the Malayan Peninsula and Indonesia. Sadly, this species disappeared from much of its range by the early 1990s, mainly due to hunting and harvesting. Its only significant remaining wild populations in Cambodia (200-400 individuals) and Indonesia (in Kalimantan) continue to face threats like habitat loss and degradation, hydropower dams, destructive illegal fishing methods, and poaching fuelled by the illegal wildlife trade. But there’s still hope for the Siamese crocodile: after more than a decade of joint conservation efforts in the Srepok Wildlife Sanctuary, researchers confirmed the discovery of hatchlings at the beginning of September 2021. It is the first-ever photographic record of a breeding population of this Critically Endangered species, showcasing what is possible to achieve when stakeholders work together in a strategic and long-term partnership. Cambodia’s Ministry of the Environment and WWF focus on the natural resource management of the Srepok and Phnom Prich Wildlife Sanctuaries via habitat and species protection, strict law enforcement efforts, monitoring, and community engagement and livelihoods support in surrounding villages. 

© ivabalk


#91 Siamese fighting fish

The Siamese fighting fish, Betta splendens, is unique not only in its beautiful colours but also in its fascinating reproductive behaviour. Before pursuing the female, the male Siamese fighting fish meticulously prepare a nest of bubbles that will provide oxygen for its developing future offspring. After chasing and finding their female mate, males fertilise the eggs, and the pair place each egg carefully into the nest. But the males’ job is not done yet – they will guard the nest until the eggs hatch, a few days later. Endemic to Thailand, this species inhabits intact marshlands in shallow zones from the Mae Khlong to Chao Phraya basins. Sadly, Siamese fighting fish populations are decreasing, mainly due to habitat degradation. Their freshwater habitats have been converted into intensive farmland and urban areas or are polluted, especially in central Thailand, which is its centre of population. They are also threatened by genetic erosion from escaped farmed stock into wild habitats. This species is very popular in the aquarium trade, being bred in many domestic variations for national and international markets.

© Dave Roach


#89 Eurasian water shrew

The Eurasian water shrew, Neomys fodiens, is one of the few venomous mammals left in the world. With its venomous saliva, this semi-aquatic species paralyses its prey. It hunts on land or in water, where they dive in and swim at a fast pace, searching for invertebrates like crustaceans and insects. Occasionally they are known to take small fish and amphibians. Even though Eurasian water shrews don’t have webbed feet, scientists believe that the stiff hairs on their back feet and tail aid swimming by propelling them in the water. They also have a thick and water-repellent fur, which protects against the cold and wet. Biologists have recently uncovered the genetic secrets of the diving behaviour of this species and its order, Eulipotyphla, which means truly fat and blind. They are the most aquatic of all European shrews, living in small holes  in the banks of their watery habitats. These include many wetland habitats, including lakes, rivers, streams, marshes, and bogs. This species is solitary and highly territorial, with males only leaving their turf to search for females in the breeding season. They extend from the British Islands eastwards to Lake Baikal, Yenisei River (Russia), Tien Shan (China), and northwest Mongolia. They are also found in the Mediterranean, from northern Spain to Bulgaria. Although generally abundant and assessed as Least Concern, there are records of local population declines most likely due to wetlands loss and degradation (e.g., drainage, pollution).

© Simon Legniti


#88 Yellow-bellied toad

The Yellow-bellied toad, Bombina variegata, is a rather small aquatic species with a vibrant underbelly. The bright yellow is a warning signal to predators, as this species presents toxins on their warty skin. When potential predators are around, the Yellow-bellied toad plays dead by throwing itself on the back and showing the coloured belly to the predator. As they can't stretch their tongue out of their mouth, they don't hunt flying insects. Instead, they pick up those that fall into the water or predate smaller insects and ground animals at night on land. They inhabit many types of wetlands (lakes, ponds, swamps, rivers, among others) in the uplands of Western, Eastern, and Southern Europe (Carpathian, Balkans, and Apennine mountains). Although listed as Least Concern by the IUCN Red List of Threatened Species, their last global assessment is from 2009, and their populations are locally threatened. They are listed as Critically Endangered in Germany and extinct in Belgium, mainly due to habitat loss and fragmentation. Discharge of pollutants into wetlands is also a threat, but they show signs of tolerance to slight water pollution. Yellow-bellied toads are declining steadily since the 1990s and increasing pressures on their habitats like plans to build hydropower dams in the last free-flowing glacial river in the European Alps - the Isel River in Austria – threaten theirs and freshwater biodiversity's existence.

© The Wildlife Association of South India


#85 Hump-backed mahseer

The Hump-backed mahseer, Tor remadevii, is the largest of the iconic mahseer species. Endemic to the River Cauvery, this species is the most widely recognised fish in India and is worshipped as a god by the Mullukuruma people of Wayanad, Kerala. But its mythical status goes beyond India’s borders - it has lured anglers from all over the world since the 1970s. Anglers have had an important role in conserving this freshwater mega-fish. The income generated from international anglers visiting the Cauvery supported the transformation of former poachers into angling guides and river guardians, motivating them to protect the mahseer and their lucrative new income stream. Also, scientists analysed the detailed catch-log books kept by angling camps in 2015 and found that the mahseer population was in decline. This evidence supported the formal recognition of the Hump-backed mahseer as a separate species and its classification as Critically Endangered by the IUCN Red List of Threatened Species. It became possible to assess that the Hump-backed mahseer was reduced by more than 90% over three generations, mainly due to the introduction of non-native species, habitat degradation, and illegal and unsustainable exploitation. Anglers and other local and international stakeholders play a crucial role in bringing the species back from the brink of extinction. The Mahseer Trust released a cartoon story to share some insights from their long-running research and interviews with the indigenous people of Wayanad, whose rich cultural heritage respects and helps to protect the priceless Hump-backed mahseer. 

© Charles J. Sharp, CC BY-SA 4.0



Contrary to what its name might suggest, the beautiful Amazon kingfisher, Chloroceryle amazona, can be found from Mexico to Argentina. Although described in the Amazon, this species has been abundant in many regions of South America, having cultural significance and even becoming the bird-symbol of Florianópolis, a city in the South of Brazil. This petite bird species is resident (non-migratory) and inhabits rivers and the edges of ponds and lakes, favouring smaller and slow-flowing rivers and creeks. Amazon kingfishers are generally found in pairs or singly, especially when fishing. Their strong beak is specially adapted to capture fish, and they are often seen perched on a branch or rock close to water before plunging headfirst after their favourite prey. They breed by streams and build holes in ravines near the water bodies, using them for nesting. Males attract females by offering them food, and the pair can stay together for years. They look very different from each other – males have white underparts apart from a broad chestnut breast band and some green streaks on the flanks, while females’ plumages are less bright and with white underparts and green patches on the side of the chest and green flank streaks. Their population is vast but with a decreasing current trend, being listed as Least Concern by the IUCN List of Threatened Species.

© Ryan Francis


#86 giant river prawn

The Giant river prawn, Macrobrachium rosenbergii, is the largest member of the Macrobrachium genus, which means “big arm”. This freshwater species can live up to approximately three years. It depends on brackish water on larval stage, inhabiting coastal rivers and estuaries. Found in Southeast Asia, its natural range extends from Pakistan up to Borneo and Java. It is a food source in subtropical and tropical regions and one of the most economically valued freshwater prawn species for aquaculture, representing 3% of total global crustacean production in 2016. Although this river giant is extensively fished, it is listed as Least Concern by the IUCN Red List of Threatened Species due to its wide natural range, likely overlapping with protected areas. However, aquaculture can bring risks to non-native habitats when species like the Giant river prawn “escape” and start successfully breeding populations. There are widespread reports of Giant river prawns establishing populations, but up to this point, it is not known if these invasions have had any negative impacts.

© Belowwater.com / Oliver Lucanus


#84 Zebra catfish

Brazil's dazzling Zebra catfish, Hypancistrus zebra, is endemic to a small portion of the Xingu River, a tributary of the Amazon. Due to its attractive black and white stripes, Zebra catfishes are highly sought for the aquarium trade where they are better known as Zebra plecos, and it was exported from Brazil in great numbers for years. But it was caught and sold at such an unsustainable rate that the government banned its export and added the Zebra Catfish to the Brazilian Red List of Threatened Species in 2004. The last assessment from 2014 places this species as Critically Endangered. In 2016, Brazil proposed H. zebra at the CITES conference for protection under Appendix III. However, this Appendix doesn't impose a complete trade ban or affect interstate trade within a country. In addition, the ongoing ban has led to a thriving black market, even though the Brazilian government aimed to reduce ongoing smuggling via neighbouring countries. To make matters even worse, the only freshwater habitat of this species is under pressure from hydropower dams. Contradicting some of its own efforts to save the Zebra Catfish, the government greenlighted the construction and operation of the controversial Belo Monte hydropower dam in the Xingu River. The dam's presence is already showing some negative effects in the region, such as a drop in water levels. H. zebra is now bred in large quantities in high-tech facilities in Asia. But without urgent action, this and many other fishes will be those born and raised in aquaria.

© Jonathan Frank


#83 Rogue mushroom

This fungi species seems to have gone “rogue" – it's the only reported aquatic gilled mushroom! More than 600 known freshwater fungi are known, but they are usually microscopic and do not produce visible fruiting bodies like mushrooms. It is very rare to find members of the Basidiomycetes that can grow underwater, especially submerged and truly gilled mushrooms. During a family picnic in 2005, hydrologist and professor Robert Coffan from Southern Oregon University discovered this intriguing species in the Rogue River in Oregon. Prof. Coffan reached out to colleagues (mycologists), and five years later, the Rogue mushroom was described as a new species as researchers confirmed this species' unique DNA fingerprint. But there's still much to learn. P.aquatica breaks down dead organic plant matter and usually grows on wood as a substrate. But scientists are still investigating how this species breathes and releases its spores to reproduce, as all the other gilled mushrooms do it through the air. One of the hypotheses is that in addition to buoyantly stabilizing P.aquatica underwater, the large gas bubble trapped under the mushroom cap provides a chamber wherein spores eject. But then spores could flow downstream to the ocean, leading to another hypothesis that aquatic insects could be dispersing them as their larvae have been observed grazing and filter-feeding on the mushroom. The bubble could also function as a type of external lung, facilitating oxygen exchange. The Rogue river is notoriously highly oxygenated, which may limit the mushrooms’ distribution; so far, only two populations have been found.

© Jan Hamrsky


#81 Large red damsel

The Large red damsel, Pyrrhosoma nymphula, is one of the most common damselflies in Europe’s wetlands. But be aware, they are very similar to another species: the Small red damselfly, which is less red. Large red damsel males are bright red with a black thorax, but females can be almost entirely black. Most likely, you will see the active and robust Large red damsel flying over or near slow-flowing and standing waters. However, in eastern and northern Europe, where it is less common, it mostly reproduces at running waters. They also have smaller numbers in north Morocco, northern Tunisia, and the mountains of Southwest Asia. They like breeding mainly in a wide variety of wetlands, from acidic bog pools to brackish ditches, especially sheltered waters with abundant aquatic plants. Their aquatic nymphs (or naiads) have elongated abdomens that terminate in three leaf-shaped tracheal gills. These fascinating gills can absorb dissolved oxygen from water and function as fins during the undulating swim of the larvae. Damselfly nymphs tend to stay for one year underwater. When it’s time to emerge, they crawl onto the shore or cling to an emergent aquatic plant and shed into adults. Shed skins are a common sight on waterside vegetation, especially for Large red damselflies, as most adults emerge from the pond at the same time over a short period in the spring. 

© Erik Garcia-Machado


#82 Cuban gar

Also known as Manjuarí, the Cuban gar, Atractosteus tristoechus, is the rarest of all the seven known gar species. The gar family is quite unique - their eggs are toxic (to mammals, birds, and most arthropods, but not fishes!), and their lineage dates back to the dinosaurs’ age like the Sturgeons. Endemic to Cuba and the nearby Isle of Youth, the Manjuarí can grow up to two meters long. It lives in shallow streams, swamps, crystal-clear springs, and cascading waterfalls. This species is the most understudied gar and the most threatened. Assessed as Critically Endangered by the IUCN Red List of Threatened Species, Cuban gars’ declining populations face threats associated with introducing invasive species, habitat loss and alteration, and overfishing of prey items. A recent assessment shows that Cuban gars share their home with other 79 species of freshwater fishes, of which 54 are endemic to the two largest islands, Cuba and Hispaniola. It also revealed that 45% are threatened with extinction. The arrival of invasive species like the African Catfish, Clarias gariepinus, resulted in the steep population declines of the Manjuarí. As apex predators of some freshwater ecosystems such as the Zapata Swamp - the largest wetland in the Caribbean - Cuban gars support the presence and endurance of other native fish populations. Hence, the Manjuarí is a crucial species for conservation efforts, as it is a key species for maintaining their ecosystems’ health. 

© Mikolji


#79 Maripano piranha

Pristobrycon careospinus is a rare piranha locally called Maripano by the Piaroa ethnic group in Venezuela. The rare photo - actually the first live pictures of this species! - was taken by the Photographer Ivan Mokolji, who explains how he managed such a difficult task on this great article. Found in the Atabapo river in the Orinoco basin, this species is part of the Serrasalmidae fish family - piranhas and pacus. Serralmids are keystone ecological taxa - some species are top riverine predators and/or primary seed dispersers in the flooded forest. Piranhas are notoriously famous for their ferocity, mainly due to feeding on corpses and nipping bathers to defend their nests. While piranhas are indeed generally carnivorous, some species like the Maripano are facultative frugivores: they can eat both other animals (e.g., insects and fish) as well as fruits, seeds, and leaves. Despite their keystone status and commercial significance throughout South America's Amazon, the ecology of piranhas and pacus are poorly understood. Pristobrycon careospinus is known from only the original description with a single specimen captured in 1974. Hence, records such as Mokolji's are essential for freshwater biodiversity assessments and conservation.

© Karine Aigner/WWF-US


#78 Gharial

The gharial, Gavialis gangeticus, is a specialist fish-eating river crocodilian generally about 3 meters long, but some may reach more than 6 meters. With seasonal migratory behaviours and social hierarchies, gharials come together for mating and nesting during the dry season in the highly seasonal, monsoonal rivers in which they live. On the sandbars and river banks, females lay an average of 40 eggs in a hole nest, and for 1 to 2 months, they will look out for them typically together with one single large male. The females open the nests at the time of hatching, and hatchlings from multiple nests aggregate in “crèches,” numbering from hundreds to a thousand or more. Once the monsoon waters start to rise, adults migrate while the hatchlings disperse widely into the aquatic shorelines. Gharials were once very common and abundant in the main rivers and tributaries of the Indus, Gangetic, and Brahmaputra-Meghna Basins. Sadly, they are currently only found in India, Bangladesh, and Nepal and are regionally extinct in Pakistan, Myanmar, and Bhutan. According to IUCN, gharials are Critically Endangered mainly due to dams and barrages which disrupt river flows , mortality in fishing nets, and historical and unregulated hunting for their skin. Nowadays, threats also include sand mining and boulder removal. WWF-India conservation efforts include a gharial reintroduction programme in India in collaboration with the Uttar Pradesh Forest Department. WWF-Nepal started a Gharial Conservation Action Plan for Nepal in 2018. 

© Barthlott, Univ. Bonn


#80 Cape pondweed

Cape pondweed, Aponogeton distachyos, is an aquatic flowering plant endemic to Western Cape in South Africa. This species produces floating leaves and flowers from stems growing at the bottom of water bodies, where it’s rooted. Typically blooming in small ponds from fall to spring, its flowers are known to be vanilla-scented and often visited by pollinators like bees. Humans also appreciate their flowers – it’s a delicacy in South Africa where they are  commercially grown for their edible roots, stems, and flowers. This species is present in traditional dishes, where the flowers and leaves work as replacements for cabbage in stews and young shoots as an alternative to spinach or asparagus. It is also used for traditional medicines, the stems as a soothing treatment to reduce redness from burns and wounds, and together with flower petals for acne treatment. Due to its attractive flowers, it is also an ornamental plant. Sadly, such a feature has also led to the introduction of this species in other parts of the world. Invasions of non-native species are a threat to the economy and can cause systemic ecological damage. In freshwater ecosystems, invasions are occurring at a fast pace, and their impacts are enhanced by increased nutrient levels, loss of top predators, and altered flow regimes. 

© Doug Perrine


#76 Amazonian Manatee

The Amazonian manatee, Trichechus inunguis, is the only manatee to occur exclusively in freshwaters. It is also the smallest and most slender member of the manatee family, distinguished by smooth rubbery skin and large flippers lacking nails. Endemic to the Amazon Basin, its range unevenly covers over an estimated 7 million km2 – from the headwaters in Colombia, throughout Ecuador, Peru until the Amazon’s mouth in Brazil. They prefer murky and calm waters away from human settlements. As herbivores, they feed on a large quantity (8-15% of their body weight daily) of aquatic and semi-aquatic vegetation during the rainy season. All food is stored up as fat, supplying them during the dry season - when the water levels start to drop, individuals migrate from the flooded areas to deeper water bodies with less available food. On the other hand, they are less vulnerable to hunting and predators. Females are very attentive mothers, teaching the young to swim, select plants to graze, and surface to breathe. Due to this process, she will only produce offspring once every four years. Listed as Vulnerable on the IUCN Red List of Threatened Species and decreasing numbers, this species is threatened mainly by historical and current hunting, especially for its meat. Entanglement in fishing nets and habitat alterations (e.g., pollution and dams) are also threats. Data is limited due to their secretive behaviour, which hinders monitoring and conservation strategies. Conservation efforts by WWF in the region include monitoring projects via drones and satellites. In Peru, WWF has recently worked with Prodelphinus to support the government in building the National Action Plan for the Conservation of River Dolphins and  Amazonian Manatee approved in 2018

© naturepl.com / Pete Oxford / WWF


#74 Titicaca water frog

Meet one of the world’s largest exclusively aquatic frogs: the Titicaca Water Frog, Telmatobius coleus. Endemic to Lake Titicaca in Peru and Bolivia, this species spends its entire life underwater. Found at depths of up to 100m, Scientists believe Titicaca water frogs can breathe through their loose-fitting skin, which performs all gas exchange. Listed as Critically Endangered on the IUCN Red List of Threatened Species, this species population has declined dramatically recently due to harvesting for human consumption, degradation of its habitat (e.g., pollution from mining and agriculture), and water extraction. Its larvae are also thought to be predated by introduced non-native trout species. Humans harvest the Titicaca water frog for food and traditional medicine, being used as an aphrodisiac and treatment for memory loss and asthma, among others. In 2016, 10,000 Titicaca water frogs were found dead along the Coata River, one of the Lake’s tributaries, probably due to the river’s pollution. Although the Lake is under habitat management and protection, further action and better enforcement are needed. Recently, two dozen women – artisans who used to poach these frogs – started knitting frog toys and finger puppets to help protect the frog and the environment with the support of the Denver Zoo. 

© Belowwater.com / Oliver Lucanus


#77 Freshwater pufferfish

Pufferfishes are also in freshwaters – meet the Freshwater pufferfish, Tetraodon mbu. Freshwater pufferfishes inhabit large rivers and lakes, feeding mainly on molluscs and insects. This species is widely distributed in the Congo river basin, besides living in the delta and lower Malagarasi River in Tanzania. In this restricted range, it is listed as Vulnerable by the IUCN Red List of Threatened Species due to increased agriculture and land-use change. Overall, their population trend is unknown, and conservation efforts would benefit from research and monitoring of the Congo basin. Pufferfishes present many fascinating features, one of the best known being their defensive behaviour against predation in which they inflate their bodies, looking like a colourful floating balloon. By swallowing water, they can reach a volume almost four times their average size. They are also among the most poisonous fish in the world – they have potent neurotoxins, which can cause fatal human intoxication. Some freshwater puffer species present a high level of toxins on their skin, but further studies on the Tetraodon mbu are necessary to give us a clearer picture. 

© Damien Brouste


#75 Dumbéa River pipefish

Freshwaters also have beautiful colourful pipefishes - meet the Dumbéa river pipefish, Microphis cruentus, endemic to New Caledonia. Closely related to seahorses, freshwater pipefishes mainly inhabit tropical and temperate seas. But there are a few species in the Indo-Australian Archipelago restricted to freshwater, such as the Dumbéa river pipefish. Known from the lower reaches of the Dumbéa River, this species likely feeds on small benthic and planktonic animals like insect larvae and crustaceans. Similar to other pipefishes, Dumbéa females deposit their eggs underneath the male's trunk or tail. And the male is the one that does the work of incubating them for several weeks in either partly or wholly concealed pouch. Not much is known about this species, being listed as Data Deficient by the IUCN Red List of Threatened Species. Recently, Shoal - an organisation dedicated to conserving freshwater species – launched the Search for the Lost Fishes campaign. They considered adding this species to the Top 10 Most Wanted species, as it hadn't been seen for a decade - or so they thought. Glady, thanks to the naturalist Damien Brouste, who recorded the Dumbéa on the citizen science and naturalist platform iNaturalist, Shoal discovered that this species wasn't a lost fish

© Jan Hamrsky


#73 Moss animal

Cristatella mucedo is a small freshwater invertebrate which is part of Bryozoa phylum, sometimes known as moss animals. C. mucedo has a wide range and is distributed across America, England, Norway, Poland, New Zealand, and likely many other places. As they are not as well studied as other species and we still have lots to learn about these bryozoans. This species likes stiller waters such as lakes, ponds, and slow flowing streams and rivers and is generally found up to 2m in depth. It grows on submerged substrates as colonies of genetically identical individuals called zooids. Each zooid is about 2 mm long and has a horseshoe crown with 80-100 ciliated tentacles, which it uses to capture and filter organic particles. Zooids form clear, soft, gelatinous colonies resembling a caterpillar. Most bryozoan colonies are strictly sessile, but C. mucedo is somewhat mobile – it moves a few cm/day by sliding, and scientists presume that a thin fluid secreted by its cells helps them glide. But it may be that muscles in the colony bottom wall also play a role. They are primarily asexual and reproduce via small encapsulated structures called statoblasts, which potentially form new colonies. Water currents, wind, and animals like fish and aquatic birds disperse the statoblasts. This tiny invertebrate generally does not like polluted waters, and its presence indicates good water quality.

© Jaime Rojo / WWF-US


#72 Giant South American river turtle

Podocnemis expansa, the Giant South American river turtle, is one of the biggest freshwater turtles of South America, reaching over 80 cm in shell length and 65kg in mass. This impressive species used to be abundant in most rivers of the Amazon and Orinoco basins, occurring across eight countries. They would migrate by the thousands up rivers to nest collectively on high sandbars, including hatchlings that tag along with the adults to feeding areas sometimes many miles away. The hatchlings and females are able to communicate with each other through underwater vocalizations. Although the freshwater giant is currently listed as Lower Risk/ Conservation Dependent by the IUCN Red List of Threatened Species, the IUCN Tortoise and Freshwater Turtle Specialist Group (TFTSG) recently recommended the categorization change to Critically Endangered. Giant South American river turtles are historically a valuable source of food and income, especially in riverine communities. Large-scale commercialization only started after Europeans arrived in the region, leading to the overexploitation of eggs and meat for consumption and oil extraction. These threats have decimated populations of this river turtle across its range. The construction of mega-dams is also an issue, hindering its recovery. Long-term conservation efforts by the Brazilian Government and other institutions led to the stabilization of some populations through the protection of areas (reserves) and the release of huge numbers of hatchlings from protected nests. However, to increase their number to viable populations, best practices should include protecting the entire river basin, besides improving monitoring and enforcement.

© Jan Hamrsky


#71 Lister's river snail

The charming Viviparus contectus is part of a family of river snails – the Viviparidae. The family name is due to their ovoviviparity: they bear live young - their offspring hatch from the eggs inside the female's body. As a gilled snail, Lister's river snail can breathe underwater - it allows water to enter the shell and go through its gills to obtain dissolved oxygen. Due to this ability, they are also able to filter water like mussels. This trait is important in polluted waters, where increasing temperatures combined with rising nutrient inputs tend to intensify eutrophication symptoms. V. contectus feeds on organic particles and microbes and lives in large slow-flowing rivers, large drainage ditches, fenland dykes, ditches on grazing marshes, and large ponds and lakes. This species is widespread in many countries in the Palearctic region, but there are considerable gaps in the taxonomy. They can host different groups of parasites, including those of medical importance. This species has been used as a traditional medicine in Korea and China for liver diseases and alcohol poisoning. The latter country also uses it as a food supplement since it contains high amounts of protein, essential amino acids, taurine, calcium, iron, and zinc. This freshwater snail is also part of the aquarium trade, but the main known threats are pollution and habitat loss. They are listed as Least Concern by the IUCN Red List of Threatened Species and with a decreasing population trend. 

© naturepl.com / Andy Rouse / WWF


#70 White-throated Dipper

The White-throated dipper, Cinclus cinclus, is one of the few riverine songbirds worldwide. Found widely across Eurasia, this territorial bird likes fast-flowing, clear-water rocky streams, and rivers with abundant freshwater invertebrate prey. It also uses glacial lakes and shallow watercourses - their freshwater habitat has to have riffles and exposed rocks for breeding. They set their large globular nests made of moss and dry leaves on rock crevice or cliff ledge, sometimes even behind waterfalls, but almost invariably over running water. Mostly found in uplands, this species is resident but does some post-breeding movement to more lowland rivers or sometimes to the coast. It's fascinating to see them in the wild – they are often bobbing when standing, as they are dancing to some unheard music. They generally plunge into the water to feed and  they can also submerge completely! They can swim against the current by walking on the river bottom, using their wings to stabilize themselves as water flows over them. Listed as Least Concern by the IUCN Red List of Threatened Species, they are not globally threatened, but their populations are decreasing mainly due to pollution. White-throated dippers are widely recognized as environmental indicators - their status and abundance strongly reflect the water quality and rivers' habitat structure.

© PietervH


#69 fishing cat

Not all cats dislike water – the Fishing cat, Prionailurus viverrinus, is strongly associated with wetlands and, as its name implies, it often enters the water to fish. Their exceptional dietary choice among felids suggests even some morphological adaptations such as semi-retractile claws that can grip slippery aquatic prey and a double-coated fur, which prevents the body from getting wet. But this nocturnal and elusive cat also preys on frogs, crustaceans, snakes, birds, and scavenges on carcasses of larger animals. About twice the size of a typical house cat, this species preferred habitat is wetlands, which destruction and degradation have led to its populations' decline. Listed as Vulnerable by the IUCN Red List of Threatened Species due to threats such habitat loss (from urban encroachment) and other threats such as wetland drainage for agriculture, pollution, and logging, which has lead to the eradication of Fishing cats from much of their previous range across South and Southeast Asia. Since 1970, the world has lost approximately 87% of its wetlands, and those remaining are disappearing three times faster than forests. A healthy population of fishing cats, and their prey, can only be sustained in a healthy environment. Learn more with this great read.

© Ulf Gotthardsson


#68 Freshwater pearl mussel

The Freshwater pearl mussel, Margaritifera margaritifera, can often live for more than a century, even two! In Sweden, scientists recently discovered the oldest known specimen, which is 280 years old. They have a complex life cycle, which depends on salmonid fish exclusively. Males release sperm into the water, and the female inhales it to fertilize its eggs. Within its gills, the female pearl mussel broods the eggs developing into microscopic larvae called glochidia. When the temperature starts to rise during summer, it releases the glochidia as a stress response. The timing is perfect - it coincides with the presence of salmonids, so the 4 to 60 million glochidia can find a fish to be their host. Just as the fish takes in water to pass over its gills to breathe, the glochidia snap into the fish’s gills. As a defence mechanism, the fish creates a cyst around the glochidia. They stay until the following spring or summer when they are juveniles, dropping off the fish into the river’s gravel, where they become adults. Found in North America, Europe, and Siberia, this species is listed as Endangered by the IUCN Red List of Threatened Species. Their populations are declining due to pollution, river regulation, and habitat degradation including dams, which also affect salmonid populations. Their conservation benefits the entire riverine ecosystem - they are excellent indicators of ecosystem health and filter up to 50 L of water a day, improving water quality. 

© Adam Leaché


#67 Afia Birago's puddle Frog

The Afia Birago's puddle Frog, Phrynobatrachus afiabirago, is named after the mother of Ghana's first formally trained herpetologist, Dr. Caleb Ofori-Boateng. Dr. Caleb discovered the endemic puddle frog in the Atewa Forest's swampy habitats in Ghana – a unique area of mountain forest-like vegetation in West Africa. This puddle frog likes large forest ponds and swamps, presumably breeding in the water. Its population inhabits only two known sites, and it's likely to be decreasing due to the ongoing decline of the extent and quality of their habitats. In 2016, a wave of bushfires destroyed most of the forest habitat close to one of the frog's ponds. Listed as Critically Endangered by the IUCN Red List of Threatened Species in 2019, Afia Birago's puddle frogs face threats such as ongoing illegal logging, artisanal mining, and farming. Scientists estimate that 80% of the already small population will disappear in the next ten years if bauxite mining plans in the Atewa Forest Reserve move forward. Dr. Caleb and many environmental Civil Society Organizations argue that mining in that region would be catastrophic to biodiversity and human health as Atewa is the water source for over five million people. Finding the endemic frog secured Atewa Forest Reserve's designation as an Alliance for Zero Extinction site, restricting mining as an activity in this habitat which is already a Key Biodiversity Area. Also, together with Synchronicity Earth, Dr. Caleb started an amphibian monitoring programme in the region. 

© Mikolji


#65 Splashing tetra

The Splashing tetra, Copella arnoldi, is an extraordinary fish species – it lays its eggs on land! At the water's surface, females and males lineup side by side and jump together out of the water to spawn. Females lay their eggs on hanging leaves, and males fertilize them immediately. The male is then tasked with keeping the eggs moist by splashing them with its tail for around three days until they hatch and fry fall into the water. The unique breeding behaviour and parental care can be seen in the Orinoco and Amazon rivers in South America - this species native range. They have high commercial importance as ornamental fish in the region. According to the Brazilian Red List of Threatened Species, the Splashing tetra is listed as Least Concerned. However, the last assessment was made in 2014, and their freshwater habitat is under pressure mainly from hydropower dams. 

© Andrey Nekrasov / WWF


#66 Russian sturgeon

The Russian sturgeon, Acipenser gueldenstaedtii, was once widely distributed in the Danube river. Now, it is listed as Critically Endangered by the IUCN Red List of Threatened Species, and it is the most endangered sturgeon species of the four that still exist in the Danube river. This species likes to swim in deep parts of large rivers, spawning on stone or gravel bottom in areas of strong currents. They would migrate a considerable distance upstream before spawning, going as far as Bratislava. Most of their spawning sites have been lost due to dam constructions, except in the lower Danube river. But this species also faces other huge threats in one of their last safe reproductive harbors: illegal poaching and trade. A new WWF market survey found that one-third of sturgeon caviar and meat products were sold illegally in the lower Danube region. Out of 27 samples from poached sturgeons, 22% were from Russian sturgeon – a very high amount considering the extreme scarcity of this species in the wild. Stopping the illegal trade is one of the key pillars of WWF’s global Sturgeon initiative. In 2019, WWF Bulgaria released thousands of farmed young Russian sturgeons into the Danube. But that is not enough to ensure their protection. WWF’s conservation efforts also include reducing pressure on their remaining populations by addressing poaching and ensuring their freshwater habitats are healthy.

© Jan Hamrsky


#64 Green hydra

The Green hydra, Hydra viridissima, is a freshwater species of cnidaria – a “relative” of the jellyfish. Green hydras are no more than 3 cm long and green due to the presence of symbiotic Chlorella, algae known to provide a significant nutrition source to cnidarians. Found at depths from shallow waters to 60m, Green hydras are widely distributed throughout the world’s ponds, rivers, and slow-flowing parts of streams and rivers. These tiny hydras are solitary polyps without the medusae phase, and their bodies only have two layers of cells. Still, they have regenerating capabilities - when subjected to pressures in the environment, they may lose body parts like their tentacles and later build them back up. Some scientists believe that they might even live forever under the right conditions – in the wild, they face disease, predators, and water contamination. Research shows that they don’t show any signs of deteriorating with age, unlike most multicellular species. They are sensitive environmental indicators and play an essential role in freshwater food webs, especially as predators when abundant. Green hydras use their tentacles to catch prey, which has stinging cells called cnidocytes that immobilizes it. Curiously, hydras only have a mouth when it’s time to feed – their mouth is not a permanent opening, vanishing after feeding. Between the ring of tentacles, a small mound called hypostome has a group of cells morphologically distinct. To open and close its mouth, these cells change shape, becoming longer and narrower to widen the gap and returning to their original form to close it – a similar process to when the pupils in your eyes dilate and constrict. 

© Cai Yixiong / NParks


#63 Singapore freshwater crab

Singapore freshwater crabs, Johora singaporensis, are smaller than the size of a thumb, growing 2 to 3 cm. Endemic to Singapore’s freshwater habitats, this species hides under rocks along river edges and inside clumps of leaves and detritus. They feed on plant detritus and oligochaete worms present in the soft stream's mud. Listed as Critically Endangered by the IUCN Red List of Threatened Species, this species is sadly among the world's most threatened species. They prefer relatively clean and fast-flowing streams in the highlands, which are at higher risk due to habitat loss and habitat acidification. Conservation efforts include measures to increase this species' wild populations, led by the Freshwater Crab Working Group in Singapore. NParks (National Parks Board) of Singapore has successfully hatched more than 150 crablets in captivity and has begun to release these captive-born individuals into the wild. In 2018, in partnership with Singapore’s National Parks Board (NParks), WWF highlighted 10 threatened species in Singapore currently under active conservation, including the tiny Singapore freshwater crab.

© Jan Hamrsky


#61 Freshwater sponge

Spongilla lacustris is one of the 248 known freshwater sponge species occurring globally. S. lacustris is the most common and widespread freshwater sponge species and the most abundant in Central Europe. It lives in rivers and preferably lakes, often growing attached under rocks or logs. Its colour is mostly white, but it can look greenish due to symbiotic algae. Freshwater sponges are subject to harsh environmental conditions, having developed a dormancy mechanism. When exposed to excessive cold or harsh situations, they form highly resistant gemmules that remain viable after the other part of the sponge dies. Once conditions improve, the gemmules germinate into a new sponge. These ancient invertebrates are sessile (fixed in one place) and filter water to feed on small aquatic organisms like protozoa, bacteria, and other free-floating life. A finger-sized specimen of S. lacustris can filter more than 125 l of water in a day. They are prey to ducks, crayfish, and various macro-invertebrates. Sponges play a key role in recycling organic matter and contribute to the primary productivity of freshwater ecosystems. Their presence in an ecosystem can be an indicator of  good water quality.

© David Lawson / WWF-UK


#62 Baikal seal

Baikal seals, Pusa sibirica, are one of the few species of seal restricted to freshwater. Located near the Mongolian border in southern Siberia, Russia, Lake Baikal is the oldest (25 million years) and deepest (1,700 m) lake in the world, containing 20% of the world's total unfrozen freshwater reserves. These freshwater seals are mostly confined to the lake, although they travel short distances into rivers flowing into and out of the lake. They are amongst the smallest of the seals (ranging between 1.1-1.4 m and weights of 50 to 130 kg), and may have the greatest longevity. Approximately 10% of the population is over 20 years old - with records of males reaching 52 and females 56 - and they continue to produce pups until they are 43-45 years old. During winter, they are mostly solitary and spend much time in the deep water under the ice, making and maintaining breathing holes to allow them to feed. Females with pups or that are pregnant are more likely to be on the ice, building dens to protect their offspring from predators. Baikal seals generally dive for a couple of minutes, but they can dive for longer - the longest recorded dives were over 40 minutes during winter. They are threatened by contamination from organic pollutants coming from the growing industrial activity in the Baikal watershed. 

© Michel Roggo / WWF


#59 Arapaima

Native to the Amazon, the Arapaima, Arapaima gigas, is one of the largest freshwater fish globally - it can grow up to 3m, but nowadays it’s rare to find a specimen more than 2m long. Its Brazilian name, 'Pirarucu,' comes from two indigenous words – pira means fish and urucum means red, referring to the reddish marks towards the tail-end. During the mating season, males' red colours become more intense. After pairing, males clean the river bed with their jaws by pulling out any weeds or obstacles in a selected area, where they dig a puddle for the female to lay its eggs and fertilize them. The female stays nearby during the incubation period, while the male circles a bit further to scare off any predators. Arapaimas have gills and a modified respiratory swim bladder which works  like a lung – they need to return to the surface every 20 min to breathe air, making them easy to catch. They are economically and culturally important to many traditional communities. Climate change effects, habitat degradation, and increased demand on fish stocks put the Arapaima and livelihoods at risk. Local communities are leading the management and conservation of their resources with the support of the government and multiple organizations, including WWF. Check this video to see what local fishers say about the Arapaima and WWF-Brazil's work to support them. Learn more about this and other valuable freshwater fishes with The World's Forgotten Fishes report.

© belowwater / Oliver Lucanus



The Piraiba, Brachyplatystoma filamentosum, lives mostly on the soft-bottom floor of the Amazon & Orinoco rivers. The Piraiba is one of the 11,000 species of migratory fish, with records of maximum distance travelled as far as 7000 km. Juveniles float downstream where they grow rapidly. Once they reach adulthood, they migrate upstream to spawn. Due to this migratory behaviour, artificial barriers like dams can obstruct the “pathway” and reduce their ability to complete their life cycle (Learn more about migratory fish with the Living Planet Index For Migratory Freshwater Fish). The Piraiba is an essential environmental, social, and economic resource in the South American basins, and it is threatened by over-harvesting. Hence, it is imperative to conserve this species, its fishery, and its rivers - learn more about this and other beautiful important fishes with the World's Forgotten Fishes report. And check out this video to see the Piraiba swimming.

© Colin Pacitti


#58 Asian water monitor

Meet the largest aquatic lizard and the world’s second largest-lizard - the Asian water monitor, Varanus salvator, which can reach more than 3 m in length and 25kg. No lizards are strictly aquatic, but this semi-aquatic and opportunistic species lives in various water systems;  mangroves, swamps, and wetlands at altitudes below 1,000m are its most important habitats. Frequently seen on river banks and swamps, this amphibious species can dive underwater to forage and/or to escape predators. They are remarkably widespread throughout southern and Southeast Asia – researchers believe their extensive distribution and adaptability could be due to their ability to swim and cross large stretches of water and their generalist diet. Asian water monitors will eat about any animal they think they can consume - fish, juvenile crocodiles, tortoise - there are even records of them scavenging human corpses! Regularly harvested and traded as a pet and for their meat, skin, and medicinal value, this species is the most intensely traded lizard species worldwide. Between 2010-2018, the two major source countries, Malaysia and Indonesia, exported more than 2.3 million skins of wild-caught specimens, mainly for the fashion industry. It is listed as Least Concern by the IUCN Red List of Threatened Species, but their population trend is unknown (last assessed in 2009). 

© Wild Wonders of Europe / Jari Peltomaeki / WWF


#56 Dalmatian Pelican

The Dalmatian pelican, Pelecanus crispus, is one of the biggest birds in the world and the  largest of the pelican family, ranging from 1,60 to 1,80m. This huge pelican feeds mostly on fish and is widely distributed – it occurs mainly in wetlands, where it breeds in fragmented ranges from eastern Europe to east-central Asia. It nests amongst aquatic vegetation on floating or stationary islands isolated from the mainland, avoiding mammalian predators. Dalmatian pelicans are dispersive in Europe and migratory in Asia. When migrating, large lakes and wetlands form important stop-over sites. Their population suffered massive declines in the past, mainly due to wetland drainage and fishers' persecution. Disturbance from tourists, wetland alteration and destruction, water pollution are among other continuing threats. However, Thanks to conservation measures, populations increased in Europe, being downlisted from Vulnerable to Near Threatened by the IUCN Red List of Threatened Species. Nevertheless, as this species currently presents a decreasing population trend and the ongoing threats in much of their breeding and migratory range, conservation efforts must continue. The Dalmatian pelican is one of WWF’s Asian Flyways Initiative priority species. One of the aims of the Initiative is to improve ecological connectivity  in the flight path of this and other migratory bird species. 

© Ola Jennersten / WWF-Sweden


#55 Diving bell spider

The Diving bell spider, Argyroneta aquatica, is the only spider to live underwater for most of its life. This Eurasian species inhabits eutrophic lakes, ponds, marshes, swamps, and slow-moving streams. To breathe underwater, their posterior body part called opisthosome is covered by fine hairs that trap air, being covered by a silvery envelope when they dive. They use plants from the dense aquatic vegetation to anchor their underwater silk webs. With their tiny body hairs, they collect air from the surface and release it in the web, creating an air-filled bubble - the ‘diving bell’, where the air is held by the surface tension between the silk fibres. The diving-bell works as an air deposit and as a physical gill - it absorbs dissolved oxygen from the water to meet the spiders’ metabolic oxygen requirements. They also use the bell to feed - after capturing the prey (generally aquatic invertebrates and small fish) by injecting venom into its body with their chelicerae (fangs), they carry it to the bell to consume it. Females use the bell to lay their eggs – they place an egg-filled cocoon in the upper region and lay on it for protection until hatching. The offspring only leave the bell once they have developed the fine hairs to build their first tiny diving bell.

© © Staffan Widstrand / WWF



The Lowland tapir, Tapirus terrestris, has a wide geographic range - from northcentral Colombia and east of the Andes, throughout most of tropical South America. Mostly found in the tropical lowland forests and wetlands of South America, they are often seen close to water which they use as a refuge against predators as well as a place to forage or cool off. This species is known for being a strong swimmer - able to cross rivers and even dive to feed on aquatic plants. Lowland tapirs can reach the size of a small pony, growing up to 1.8m and 225kg. They are primarily solitary, using their large teeth to grind up plants, fruits, and seeds at night and resting or hiding during the day. This species is listed as Vulnerable on the IUCN Red List of Threatened Species. Main threats to this species are habitat loss due to deforestation, hunting for meat, and competition with livestock. Due to their  long gestation period and generational time, tapirs are more ecologically prone to impact from prolonged hunting activity, making population recovery more difficult. 

© Ryan Francis


#53 Arafura File Snake

The Arafura File snake, Acrochordus arafurae, is one of the 153 known species of freshwater snakes globally. You can find this species in northern Australia and Papua New Guinea - swimming in  rivers, lakes, lagoons, floodplains and their associated wetlands. The Arafura is adapted to freshwater life, being considered an entirely aquatic snake – they forage in water and cannot survive without aquatic prey. Arafura File snakes are nocturnal and non-venomous. They feed exclusively on fish, which they immobilize by constriction - as they are agile and their skin flexible (not bendy) they can easily capture and hold onto their fish prey. They have nostrils on top of their head so they can breathe whilst underwater. Listed as Least Concern by the IUCN Red List of Threatened Species, this species populations viability depends on their freshwater ecosystems health.  

© Barthlott, Univ. Bonn


#54 Giant floating fern

The Giant floating fern, Salvinia molesta, is a free-floating perennial aquatic plant adapted to stagnant or slightly flowing freshwater systems. Sadly, even though this species is native to south-eastern Brazil, humans have spread it in almost all tropical-subtropical regions, becoming problematic in many areas (southern USA, Australia, South-East Asia, the Pacific and south, central and eastern Africa). But floating species like those belonging to the Salvinia genus possess unique features that fascinate scientists and boost innovations. Their leaves present a "superhydrophobic" (i.e., extremely water repellent) behaviour - when immersed, the leaves wrap themselves in an air jacket and remain fully dry. Salvinia's surface also has an affinity for oil, which is, in a way, a drawback of super-hydrophobia. Such features have inspired studies in Biomimetics. Dr. Wilhelm Barthlott, Professor Emeritus at the University of Bonn, created a textile prototype based on Salvinia's properties to efficiently remove oil films from the water's surface without using chemicals or external energy supply (check out this video). 

© Shutterstock / Jens Goos / WWF-Sweden


#52 Common hippopotamus

The Common hippopotamus or hippo, Hippopotamus amphibious, is a well-known mammal restricted to the rivers, lakes, and wetlands of sub-Saharan Africa. Hippos love water – as their name suggests, they have an amphibious lifestyle. They spend the day mostly in the water and in groups - herds range from the tens to a hundred – only emerging at night to feed on grass and fallen fruit. Due to their dry skin, Common hippos rely on water sources to remain moist and cool. With their eyes and ears on the top of their heads, they can watch for predators while lying low in the water. They are the only mammals known to produce an amphibious call – their loud vocalization can be transmitted simultaneously through land and water. Hippos fight for territory can be brutal, in which they use their huge ivory canines. Smaller conflicts, however, are generally settled by threat displays like the famous "yawn". Listed as Vulnerable by the IUCN Red List of Threatened Species, hippos’ wild populations have decreased 30% in the last decade, and some are regionally extinct. Losing hippos could have devastating consequences for African freshwater ecosystems, as they play a key role in transporting nutrients between the land they graze and the water in which they defecate. The main threats hippos face are habitat loss and degradation and illegal and unregulated hunting for meat and their ivory teeth. They are also threatened by drought, like in the Mara River basin, shown in WWF’s report and its consequences to biodiversity highlighted in this article with WWF’s William Ojwang as an interviewee. WF Hong Kong is also working on hippos conservation, as Hong Kong is the single-biggest buyer of hippos’ valuable teeth. WWF is shedding some light on this issue by raising awareness and advocacy (read this great blog from WWF’s Thomas Gomersall to know more). 

© Zeb Hogan WWF


#51 Taimen

The Taimen, Hucho taimen, is the largest salmonid in the world - reaching lengths up to two metres. But size is not their only remarkable feature - they are top predatory species known for hunting prey in packs, earning them the nickname “River Wolves”. They also have a peculiar diet, which mostly includes fish, but also the occasional rodent and bird. Unlike many salmonids, this migratory fish is potamodromous – it spends its whole life in freshwater, in large, cold, and swift-flowing rivers, traveling upstream to smaller tributaries to spawn. But it takes time for them to grow up – Taimens take up to seven years to reach sexual maturity, and they can live for more than 30 years. This species occurs in Europe and Asia, including parts of the Caspian and Arctic drainages in Eurasia and portions of the Pacific drainage in Mongolia, Russia, and China. However, this species’ numbers decreased from much of their range, being listed as Vulnerable on the IUCN Red List of Threatened Species. Due to threats such as pollution, habitat loss, damming, and climate change, this species suffered substantial (50%) population declines since 1985. Significant populations remain only in Russia and Mongolia. Mongolia harbours part of the core habitat of one of the last healthy taimen populations in the world. These populations are primarily threatened by fishing due to the high levels of unregulated, illegal practices throughout the country. The Mongolian government has taken significant action since 2012 with protective legislation. Together with other NGOs, including WWF, they are trying to find a balance to curb poaching and promote regulated fishing and its revenue. As part of conservation efforts, WWF-Mongolia works on scientific researches, education campaigns, and public awareness. Take a look at the Mongolian Fish guidebook to know more!


© Watcharapong Hongjamrassilp


#50 parading shrimp

A long time ago, a group of indigenous people in north-eastern Thailand discovered a distinctive phenomenon called ‘parading’– the synchronous mass migration of freshwater shrimps on land. Found in rivers and streams of Asia - Viet Nam, Yunnan (China), Laos, Thailand, and Peninsular Malaysia - Macrobrachium dienbienphuense is one of the species known to parade annually. During the rainy season, these adventurous shrimps leave the water collectively at night and walk upstream on land before returning to the river. But why would they leave the water? Recent research conducted by Watcharapong Hongjamrassilp in Nam Yuen district (Ubon Ratchathani province, Thailand), tested the hypothesis that parading was associated with spawning and breeding – and it is not. Evidence shows that the shrimps might leave the water to escape strong currents. Most of the parading shrimp were juveniles  – larger adults can face a stronger current, being less likely to parade – and not ready to reproduce. They walked from 5 to 20 meters - depending on river velocity and riverbank structure -  and some even stayed out of water for 10 minutes or more. To take in oxygen while on land, shrimp stayed within the rivers splash zone (20–40 cm from the river’s edge), and their exoskeleton seemed to trap water around their gills (similar to a reversed dive helmet). This mass migration is such a fascinating scene that it has been promoted as an ecotourism event in Thailand since 1999, drawing more than 100.000 visitors annually. Even though they are listed as Least Concern on the IUCN Red List of Threatened Species, recent evidence suggests that they are decreasing in number and body size. 

© ExaVolt, CC BY-SA 4.0 , via Wikimedia Commons


#49 water boatman

You can likely find the tiny water boatman, Micronecta scholtzi, in the bottom of ponds and streams, rowing with their paddle-shaped legs. M. scholtzi is a species of lesser water boatman found in Europe. Micronecta’ means small swimmer, but the only thing small about them is their size. Despite being only 2 millimetres long, this aquatic insect can produce the loudest sound of any animal relative to its body size. Bigger animals generally create the loudest sounds – mechanically speaking, a small sound source cannot generate a high-level sound output. In terms of sheer decibels, M. scholtzi loses to whales and elephants. Yet, this little creature can still produce a sound loud enough to be heard from a riverbank several meters away, propagating it across the water-air interface. Only males can sing – they generate an extremely loud courtship call to attract females, often in a synchronized chorus. And how do they sing? Scientists believe they rub their penis against ridges on their abdomen and that layers of air around their body amplify the sound. Water boatman specimens trap air reserves through microscopic hairs as they dive to help them breathe. Such a sound-producing genitalia mechanism is relatively rare within the animal kingdom. 

© Camilo Ortega / WWF-Colombia



To say that the Green anaconda, Eunectes murinus, is fascinating is an understatement. They belong to one of the most remarkable Neotropical freshwater snakes groups - the Anacondas - known for their constricting abilities and as one of the world’s longest snakes. Green anacondas stand out as the heaviest snake – it can weigh up to about 250kg! They also have a “heavy” diet, including Earth’s biggest rodent (Capybaras - see below #39) and the occasional crocodilian (Caimans). This species is widely distributed through the swamps, marshes, and slow-moving streams of South America. Green anacondas’ eyes and nasal openings are on the top of their head, which allows them to “hide” as they stay completely submerged in the water while waiting to ambush their prey. With a lethal squeeze that halts breathing and blood flow, prey is killed and then swallowed. Green anacondas also form “breeding balls” – slow-motion wrestling matches of a dozen suitors for one receptive female, where they simultaneously coil around her until one of them gets lucky. The impregnated female retains the eggs, and her offspring emerges from the eggs before leaving her body. She then gives birth to two to three dozen live young, which are already about two feet long and almost ready to swim.


© Brent Chambers


#48 Jaguar

The iconic jaguar, Panthera onca, is the largest cat in the Americas. From Mexico to Argentina, jaguars typically inhabit regions with dense forest cover and water bodies, living near lakes, rivers, and wetlands. They are more strongly associated with water than any other Panthera cats. This majestic species is a confident swimmer known to cross large rivers, and it preys on aquatic species like turtles and even caimans. Thanks to their robust canines and a large head, jaguars can take down prey three to four times their own weight and bite through a crocodile skull or turtle shell – having the most powerful bite than any other big cats. Therein lies its name – ‘jaguar’ comes from ‘yaguar’, an indigenous word that means 'he who kills with one leap'. Sadly, they have been nearly eliminated from half of their historic range, with regional extinctions in El Salvador and Uruguay. Their preference for freshwater habitats - even within drier areas, they are only found around the main watercourses – quickly brings them into human-wildlife conflict, as they share the same resource as the expanding high-intensity agriculture and mining. Illegal wildlife trade, and habitat loss and fragmentation are other threats leading to the decreasing population of jaguars, listed as Near Threatened by the IUCN Red List. Their stronghold is in Brazil – in the Amazon region and the world’s largest tropical wetland, the Pantanal. However, the recent fires in both biomes magnify the threats to these populations - especially in the Pantanal, where a park known to hold the biggest concentration of jaguars globally has had 85% of its territory burned. 

© belowwater / Oliver Lucanus


#46 Elephant fish

Campylomormyrus curvirostris has a very long trunk-like snout and occurs exclusively in water bodies within the Congo River basin. This strange-looking fish is a species within the family of freshwater weakly-electric fishes, the Mormyrids. This - mostly - nocturnal family is known to use their electric sense to communicate, actively find objects and food, and discriminate between fish from other species and their own. A specialized electric organ in the tail base generates a mild pulse-like Electric Organ Discharge (EOD). The electric pulse helps them to create a picture of their surroundings, in a similar way bats and dolphins use echolocation. C. curvirostris belongs to a particular group within their Mormyrids family – the Campylomormyrus –, which scientists say to have EOD play a key role in pair formation and mate recognition. The species in this group show remarkable differences in terms of EOD shape and duration, which enables them to perceive differences in the EOD generated by their peers. 

© naturepl.com / Nick Garbutt / WWF


#45 Giant Otter

As the name conveys, the Giant otter, Pteronura brasiliensis, is the largest otter species in the world  - reaching lengths up to 170cm-180 cm. They live in large and slow-moving rivers, streams, lakes, and swamps throughout South America’s lowland rainforests and wetlands. Giant otters are very social, living in large family groups that do everything together – sleeping, hunting, and playing. Generally, a monogamous pair that mate for life leads the group formed by their offspring. As they are diurnal, noisy, and hang out in groups, they can be easy to see - making them highly susceptible to persecution. Giant otters were nearly hunted to extinction for the pelt trade between the 1940s and mid-1970s and lost from much of their  southern and easterly range, including Uruguay, Argentina, and several states of Brazil. Besides poaching, they currently face threats such as habitat loss, pollution, and diseases introduced by  domesticated dogs. The Giant otter is listed as Endangered by the IUCN Red List, with a decreasing population trend and a discontinuous and fragmented range due to local extinctions. Important subpopulations can be found in the Pantanal region and in the Amazon, including in Peru, where the otter biologist, Jessica Groendikj, worked on the individual identification of the Giant otter. One of this species' distinctive features is the pale markings on its neck - as unique as your fingerprints - making them identifiable from birth. 

© Jan Hamrsky (left) and Wild Wonders of Europe / Ruben Smit / WWF (right)


#44 Vagrant darter

The Vagrant darter, Sympetrum vulgatum, is a dragonfly species found in all kinds of standing, largely unshaded waters. Larvae of almost all 5952 species of dragonflies and damselflies depend on freshwater habitats, spending most of their lives in this stage (generally one or two years) in the water. The nymphs live on the bottom of still and slow-flowing waters. To fully grow into an adult, the larvae catches and eats live prey at every opportunity. Both larvae and adults are predators, playing a significant role in the cycle of materials both in aquatic and terrestrial ecosystems. The Vagrant darter is a rare migratory species with a wide distribution – you can find this species eastwards to China and Japan, in Central and eastern Europe, and is likely common in large parts of its Asian range.

© Peter Maguire


#41 Sulawesi Cardinal shrimp

The colourful Sulawesi cardinal shrimp, Caridina dennerli, is only known from Lake Matano in Indonesia (part of the Malili Lakes system - Sulawesi). However, the vivid colours of this freshwater shrimp are fading from the lake - they have not been recorded since 2013 and are listed as Critically Endangered by the IUCN Red List of Threatened Species. Reinforcing this trend, surveys conducted in 2017 and 2018 recorded not a single specimen in the lake, not even from sites where they were abundant before. Hence, this species is now considered Possibly Extinct in the Wild, being among the 1 in 3 freshwater species threatened with extinction. The Sulawesi shrimp is currently under the threat of nickel mining and hydropower installations on the outlet of Danau Matano, which impacts outflow and natural water level fluctuations. The rapidly expanding human population, erosion around the lake, capture for the pet trade, and direct predation of invasive species aggravate the problem. IUCN’s conservation efforts on the Lake Malili system aim to raise awareness and improve conservation and sustainable use by assessing freshwater biodiversity status and distribution. Shoal - an organisation dedicated to the conservation of freshwater species - is working on a Conservation Action Plan in Wallace’s dreamponds to step up the conservation sufficiently to a scale that will allow the endemic species to survive and recover. You can also learn more about the impacts on freshwater species and habitats with WWF’s Living Planet report 2020 and what you can do to help.

© Michel Roggo


#43 Sockeye salmon

For the Sockeye salmon, Oncorhynchus nerka – size doesn’t count. Even though it is among the smaller of the seven Pacific salmon species, the bright-orange Sockeye salmon migrates thousands of kilometres during their lifetime from rivers to the ocean and back again. They hatch in gravel nests in rivers or lakes of Russia, Canada, and the United States and stay in freshwater for one to three years before migrating to the ocean. They remain in the sea for one to three years until maturity - when they are ready to go back to their natal freshwater habitat, where they spawn and die. Scientists think that salmon navigate back to their natal rivers by following the geomagnetic drift, along with visual, olfactory, and environmental cues from currents, salinity, water temperature, and freshwater inputs from rivers. As with other salmonids, the Sockeye needs clean, cool, and highly oxygenated water for their sensitive eggs to thrive. Therefore, a healthy population of salmon acts as a good indicator of river health. Recently, the Living Planet Index for Migratory Freshwater Fish highlighted the 76% collapse in freshwater migratory fish populations around the world since 1970 due to overexploitation, river dams blocking their migration routes, and habitat degradation. Sockeye salmon is listed as stable by the IUCN Red List of Threatened Species; however, some subpopulations are declining, and there are cases of regional extinction. WWF conservation efforts focus on protecting salmonids and their habitats through initiatives such as Free-Flowing Rivers and programmes in the Arctic, where we work with local communities.

© La Ponte


#42 Platypus

The (Duck-billed) Platypus, Ornithorhynchus anatinus, is one of the most peculiar animals on the planet. This species uniqueness starts with the order of mammals to which it belongs - monotremes, mammals that lay shell-covered eggs but nurse their young. With its duck-like bill, webbed feet, a broad flat beaver-like tail, and an otter type of body and waterproof fur, this distinct mammal is adapted to and dependent on freshwater ecosystems. Hunting underwater, these bottom feeders have skin folds to cover their eyes and ears to prevent water from entering, and the nostrils close with a watertight seal. They find their invertebrate prey by detecting electrical signals through sensitive receptors on their bill, storing the catch in their cheek pouches until they reach the surface for consumption. They are also among the few venomous mammals – males have sharp stingers on the heels of their rear feet, using them most likely to settle territorial disputes. But don’t worry - although excruciating, the toxic blow is not fatal to humans, but known to kill mice, dogs, and other platypuses. Nowadays, you can only find the Platypus in the streams, lakes, and lagoons of eastern Australia and Tasmania – it was extinguished from much of its range due to hunting, habitat degradation, river fragmentation from dams, and entrapment or entanglement in fishing gear. 

© WWF-Malaysia / Mazidi Abd Ghani


#40 Oriental darter

The Oriental darter, Anhinga melanogaster, is a waterbird known for its ability to swim to catch fish and other underwater prey. Found in Southern Asia, this beautiful bird lives in shallow inland wetlands, including lakes, rivers, swamps, and reservoirs. With their webbed toes, darters swim with their bodies submerged, while their long and sinuous neck remains visible above water. This behaviour display gives darters a snake-like appearance – accounting for their colloquial name “snakebird”. When foraging, they move slowly or hang motionless in the water, spearing fish with their dagger-like bill. Adapted to diving in shallow waters, darters are renowned for their extremely low buoyancy. Compared to other closely-related water birds like cormorants, they have uncommonly wettable plumage, thin and less spongy skin, denser bones, and smaller air sacs. Like other water birds, they are important bioindicators for the ecological conditions and health of wetland ecosystems. The Oriental darter is listed as Near Threatened by the IUCN Red List of Threatened Species, being regionally extinct in Thailand. Their populations are decreasing due to pollution, drainage, hunting, and the collection of eggs and nestlings. As they warrant conservation attention, Oriental darters are harboured by WWF’s Orissa Semi-Evergreen Rain Forests ecoregion

© Martin Harvey / WWF


#38 Nile Crocodile

The Nile crocodile, Crocodylus niloticus, is an aquatic predator that can reach up to 6 meters. Found in eastern, central, and southern Africa, this reptile giant inhabits a wide diversity of water bodies (rivers, lakes, swamps, and coastal estuaries), including the iconic Mara river basin. WWF’s recent report on Mara’s freshwater biodiversity identified the Nile crocodile as one of the four freshwater reptiles in the basin shared by Kenya and Tanzania. This species plays a key predatory role in the perennial river, which is the only water source for migrating wildlife in a drought year. They mostly feed on fish but can attack zebras, small hippos, porcupines, birds, and even other crocodiles. This impressive animal presents a caring nature as a parent – females ferociously guard and defend their nests until the eggs hatch, often helping hatching babies emerge with their teeth and carrying them inside their mouths to the water. This species also presents other sophisticated behaviour like complex communication and coordinated group hunting, being considered highly intelligent. If you ever thought that a crocodile has a dinosaur-like feature, you were not far off - crocodilians are more closely related to dinosaurs and birds than to most reptiles. Between the 1940s and 1960s, the Nile crocodiles populations were depleted throughout much of their range due to hunting. Thanks to the protection afforded by national legislation and international trade conventions (CITES), populations have recovered in many regions.  

© Jaime Rojo Lopez


#39 capybara

The capybara, Hydrochoerus hydrochaeris, is the largest rodent on Earth. This mammal depends on freshwater ecosystems, occurring only in a habitat close to water like marshes, estuaries, rivers, and streams. They are adapted to a semi-aquatic life, using water for mating, to escape from predators, and to eat aquatic plants. Due to their dry skin (their sweat glands are not well developed), they stay in the water or under shade – especially in the afternoon - to regulate their body temperature. Capybaras have toes partially webbed to paddle around and eyes, ears, and nostrils on the top of their head to keep an eye on their surroundings. They are fundamentally social animals - female capybaras raise the offspring in groups and cooperate in their nursing. Broadly distributed, you can find capybaras mostly in South America - Colombia, Venezuela, Ecuador, Peru, the Guianas, all of Brazil, eastern Bolivia, Paraguay, Uruguay, and north-western and eastern Argentina. Their primary threat is hunting for meat and leather, with some local populations extirpated. The most recent threat is the gargantuan fires in the Pantanal – the world’s largest wetland and one of the habitats with the highest density of capybara (learn more about WWF’s actions against the fires here).

© Magnus Lundgren / Wild Wonders of China / WWF


#37 blue-spotted Mudskipper

The blue-spotted mudskipper, Boleophthalmus pectinirostris, is one peculiar fish. It belongs to a group known for its incredible ability to live in and out of water - the amphibious “gobies” fish. Thanks to adaptations like their strong pectoral fins, they can move on land in a way called “crutching” – similar to a human walking with crutches. They can also jump and climb up streams and waterfalls through their partly or entirely fused pelvic fins that function as a strong sucker. To breathe out of the water, mudskippers use their skin and chambers in their modified gills to trap air. Found in Northwest Pacific, the blue-spotted mudskipper lives in freshwater, brackish, and demersal habitats, including mudflats in Mai Po Nature Reserve’s wetlands in Hong Kong. During high tides, they stay in a burrow in the mud. They “crutch” around and browse the mudflats at low tide, being so numerous that the mud can almost seem alive. Males commonly display dramatic territorial and mating behaviours, like facing each other head-on and raising their dorsal fins as threats or to attract females. Sadly, illegal fishing and habitat degradation threaten their populations (learn more with this great read and check them out in this video).

© Patrik Oening / WWF-Brazil


#35 Piraputanga fish

The Piraputanga fish, Brycon hilarii, is renowned for its leaping ability. Endemic to the Upper Paraguay river basin, they play an important (long-distance) role in seed dispersal in the Pantanal region as they perform long pre-spawning migrations along all river drainages. The Piraputanga uses its scissor-like teeth to feed on fruits that fall in the water. They can also leap up to one (1) meter above the water to snatch fruits (and insects) from the riparian vegetation! This remarkable behaviour is a common attraction for tourists, who bait fruit above the water to see the beautiful Piraputanga leap. The Piraputanga also captivates its audience with its colour – when the light reflects on the water, the scales of Piraputangas showcase a flaring contrast of their yellow body, orange-colored fins, and red tail. They are also an essential source of income for local communities through recreational diving and fish watching, as well as artisanal or sport fishing. Sadly, the destruction of riparian forests and construction of dams negatively impacts aquatic ecosystems, threatening seasonal migratory movements of frugivorous fishes. Overfishing or other anthropogenic disturbances (like pollution) might also lead to the local extinction of fish–plant interaction, which may negatively affect the riparian forests in this region and have far-reaching implications on ecosystem services livelihoods.

© Anne Richardson


#34 raft spider

Meet the European spider of the year: the raft spider, Dolomedes fimbriatus, one of the largest native spiders in the region. Found mostly in moorland and wetlands, they inhabit water margins of ditches, ponds, and slow-flowing streams, showing remarkable adaptations to this habitat. This free-living hunter spider moves skilfully on the water surface, overpowering its prey without using a web. They sit on emergent water plants or the water surface in a hunting position, waiting for unaware (aquatic) insects, tadpoles, and small fish. Thanks to its thick coat of body hairs, the raft spider can lay its whole body on the water, relying on surface tension to remain above the water. But when in danger, they can dive underwater and come out dry – an air bubble forms around their body, which bursts after they go back to the water surface. Raft spider females constantly carry their spherical egg-sacs (with up to 1000 eggs!) in their mouthparts called chelicerae (pair of appendages in front of the mouth). When the eggs are close to hatching, the female hangs the eggs’ cocoon in vegetation near the water’s edge, guarded and enclosed by silk threads. Unfortunately, the Euro-spider of the year is becoming rarer and more vulnerable, due to the destruction of its habitat – building work on river banks and removing reed beds and water lilies - and climate change.

© naturepl.com / Mark Carwardine / WWF


#36 pink Amazon river dolphin

“Once the sun goes down, the boto morphs into a handsome young man dressed in white to seduce young women of local villages, leaving them impregnated before the sun comes up to return to the river once again as dolphins.”
That’s not the only myth surrounding the pink Amazon river dolphin, Inia geoffrensis. Also known as “boto cor-de-rosa” or boto, you can find this mystical animal throughout the Amazon and Orinoco river basins in South America (strictly speaking, also in the Araguaia basin). Unlike other river dolphins, the boto has a flexible neck that moves its head left and right to maneuver through the flooded forests for food and shelter. With their long snout, they feed on fish and other aquatic organisms like turtles and crabs. Locals believe that botos possess magical powers. If you swim alone in the river, you could be whisked away by the boto to “Encante”, a magical underwater city. For many tribes, including WWF, the boto is sacred. Listed as an Endangered species by the IUCN Red List, the magical boto can’t escape threats such as dams, mercury poisoning due to gold mining, and being killed in fishing nets or to be used as fish bait. Through initiatives such as River Dolphin Rivers  and South American River Dolphin (SARDI), WWF works with local communities, governments, and other NGOs to develop regional and innovative approaches to protecting this species and their habitats. Since they are indicators of environmental river health, the pink river dolphin was chosen as the Ambassador of the Amazon rivers! With such seductive powers, that was an easy call.  


© Barthlott, Univ. Bonn


#32 Sacred lotus

To shine some light on these trying times, we bring you the Sacred lotus, Nelumbo nucifera. This perennial aquatic plant has been revered in many cultures for thousands of years, mostly as a symbol of purity. Its name derives from its significance in the religions of Buddhism and Hinduism: a plant that rises from a humble origin, rooting itself in the muck below and ascending high above the water untainted. The leaves can sit directly or above the water, and the distinguished lotus flower blooms gloriously above the leaves. The Sacred lotus’s uniqueness is in all parts of the plant -  the roots, stems, leaves, and seeds have all been used as a food source and in traditional medicines, especially in Southeast Asia. Also known as the Asian lotus, this species has also intrigued the scientific community for presenting remarkable features such as leaf super-hydrophobicity (i.e., water repellence) -  known as the “Lotus-Effect” -, and seed longevity. Their leaves have a special waxy coating that sheds water and dirt, suggesting that the Lotus-Effect may play an important role in protecting plants against pathogens and contaminations. Lotus fruits were found buried underground over 1300 years in China could still be germinated, being seed longevity another fantastic feature of this sacred aquatic plant.

© Izzy Standbridge


#33 Harvest mouse

The super cute Harvest mouse, Micromys minutus, loves a wetland! Especially in Europe, where they are quite common in wetlands. Harvest mice make their nests in the reeds or along rivers and canal edges, and feed on seeds, green vegetation and insects. This species of rodent is an extremely active climber and has an acute hearing - they react sharply in response to rustling sounds up to 7m away, freezing or dropping into cover. But they can’t always react fast enough – their numbers have been noted to decline in many parts of Europe, particularly local populations, due to loss and degradation of wetland habitats. In Sussex, England, the Ouse and Adur Rivers Trust created the project Helping Hands for Harvest Mice Citizen Science,  where as part of a wider river restoration project, local communities have helped researchers monitor harvest mouse populations. 

© Zeb Hogan / WWF


#30 Mekong Giant Catfish

Able to reach a length of up to 3m and over 300kg, the Mekong giant catfish, Pangasianodon gigas, is one of the world’s largest fish! Native and endemic to the Mekong River, this species can live to be 60 years old. These migratory fish swim around Vietnam, Cambodia, Laos, and Thailand – most likely found in the Lower Mekong river basin. Sadly, they are one of the most endangered fish in southeast Asia. Listed as Critically Endangered by the IUCN Red List of Threatened Species, this species faces overharvesting for local and commercial fisheries, habitat loss and pollution, intentional hybridization for aquaculture, and bag-net fishery of Cambodia. In the last 50 years, the total number of fish declined by 90%. This river giant is a highly-valued food resource, not because it is a delicacy but because it has a god-like status - some believe it brings good luck forever once eaten, bestowing the gifts of wisdom and long life. Intentional fishing is currently banned in most areas, but this species is still harvested incidentally as by-catch. As the Mekong giant catfish most probably migrates long distances, dams’ construction is also a threat. Dams likely prevent them from reaching their spawning site and may cause extinction - there is only one known spawning site in Thailand, and the blockage of this waterway by two dams might be their demise.

© Lee Grismer


#28 Ywangan crocodile newt

New species are often discovered in the biodiversity hotspot region of the Greater Mekong - over 2,216 new species have been found since 1997 (that’s two species per week on average! Check this report for more). Recently, researchers discovered a new species of newt. With a coloration almost solid black, the Ywangan crocodile newt, Tylototriton ngarsuensis, differs from its bright orange cousins, besides having a shorter head, larger size, and breeding later in the year than other closely related species. Found in Ngar Su Village, in Myanmar, this amphibian is so common that the villagers have long known about it. One of the researchers, Lee Grismer, said that “even in populated areas, new species can be found and in doing so underscores the need for field work so we can more accurately catalogue the biodiversity of this planet.” Especially when these species face threats such as habitat destruction, harvest for the illegal pet trade, and medicinal trade. Besides Lee Grismer, this new species was discovered by his colleague from La Sierra University, Marta S. Grismer, Perry L. Wood Jr. (University of Kansas), Evan S.H. Quah (Universiti Sains Malaysia), Robert E. Espinoza (California State University) Matthew L. Murdoch (Villanova University, USA), and Aung Lin (Fauna and Flora International, Myanmar). 

© Jan Hamrsky


#31 Great diving beetle

The Great diving beetle, Dytiscus marginalis, is an aquatic insect generally found in still waters with dense vegetation. These ferocious carnivores can grow up to 44mm feeding on arthropods, tadpoles, newt larvae, and juvenile fishes. With dorsoventrally compressed and oval bodies perfectly adapted for swimming, diving beetles propel themselves through their legs’ synchronous strokes covered with swimming hairs. As diving beetles mostly breathe atmospheric air, they carry a bubble of air under their wings when swimming under the water surface – quite like scuba divers! Likewise, they also have to come to the surface occasionally to replenish the oxygen in the bubble. When resting underwater in well-oxygenated streams, this air bubble can function as a physical gill capable of absorbing dissolved oxygen from the surrounding water. 

© Gary Graham

#29 American beaver

The cuddly-looking American beaver, Castor canadensis, is one of the two species of beavers in the world. The North American native has darker fur and a shorter snout than its Eurasian “cousin”, but both are stars when it comes to their constructions - beavers are second only to humans in their ability to change and manipulate their environment. Living in areas of persistent water like lakes, ponds, and streams, beavers build dams and dome-shaped homes with branches and mud to protect themselves and their offspring against predators. The dams block streams and turn land into large ponds, facilitating the floating of food and building material to their homes - often strategically placed in the middle with only underwater entrances. Beavers’ leathery tails storage energy (fat) and their characteristic large front tree-razing teeth never stop growing, which they control by constantly gnawing on wood. Due to their diet of leaves and bark, to some people, beavers’ butts smell like vanilla! To waterproof and scent mark themselves, they use a special grooming paw on their hind foot to distribute throughout their fur castoreum oil - a chemical compound often the combination of castor and anal gland secretions, plus urine (watch this video to learn more about them).

© Chris van Wyk


#27 Mary River turtle

This week we bring you the mesmerizing Mary river turtle, Elusor macrurus. This captivating species can be found in flowing, well-oxygenated sections of streams in a single river of Australia – its namesake, the Mary river. One of their unique features is having an extremely long tail, which can be as long as 70% of the shell length. But what makes this funny-looking freshwater turtle even more special is its ability to breathe through its bum! The Mary river turtles have a cloacal ventilator – gill-like structures on their cloacas, which allows them to breathe oxygen underwater up to three days. Unfortunately, their unique looks are the reason they are listed as Endangered by the IUCN Red List of Threatened Species. During the 1960s and 70s, thousands of Mary river turtle eggs were harvested for the pet trade, leading to their dramatic population declines. It was their looks, on the other hand, that helped to prevent the construction of a dam in 2009 in the Mary River, which would have put them at even higher risk. The struggle, however, is far from over as the Mary river turtle continues to be threatened by feral animals, cattle grazing and water quality.

© Denis Faure


#26 Fisherman bat

This week we present a flying mammal that can also fish – the Fisherman bat, Noctilio leporinus. Also known as the Greater Bulldog bat, this fishing bat inhabits tropical lowlands from Southern Mexico to Northern Argentina, foraging over streams, ponds, rivers, and lagoons. The Fishermen bat can swim and take flight from the water, and feeds on aquatic insects, fish, frogs, and crustaceans. Many bats are associated with freshwater, but fishing bats possess adaptations of their posterior limbs to capture prey. Fishing bats tend to have 1.8 to 3.9 times larger feet, and their digits – ''toes'' - are elongated, ending with hook-like claws. When fishing, these bats fly within 20 to 50 cm of the water surface, echolocating to find ripples that signal underwater prey. Once they notice the disturbance, they fly closer over the water  (four to 10cm) with their back legs and feet held straight down, “scraping” the water to gaff fish with their forward-facing claws. With the fish in their claws, they rise in the air and transfer the prey to their mouth. The Fishermen bats are also safe “flyers” – when on a collision course with other fellow Fishermen, one bat "honks" at the other! They can do this by adjusting the frequency of its echolocation call.

© Leandro Souza


#25 Electric eel

To celebrate World Rainforest day, we present this shocking species, Electrophorus voltai. Two new electric eel species were discovered last year in the Greater Amazonia region. One of the new species, Electrophorus voltai, can generate an electric shock up to 860 V, the strongest of any known animal. More than five times the voltage of a standard American wall socket, researchers say that this shock wouldn’t kill a healthy person, although it would definitely not be pleasant and result in a brief muscle contraction, then numbness. Electric eels generally use their electric discharge to detect other fish and paralyze prey. The researchers, however, also found that electric eels seem to coordinate their predatory activity; they surround the fish as a group, release electricity, and kill it. If you want to know more, check out the scientific paper here.

© Jan Hamrsky


#24 Water scorpion

The Water scorpion, Nepa cinerea, might look like it, but it is not a true scorpion. With its leaf-shaped and flattened body, this intriguing species is actually a water bug – an insect adapted to freshwater ecosystems. Frequently found in the Palaearctic region – a large ecozone including Europe, Asia, northern Africa, and the north and central parts of the Arabian Peninsula – the Water scorpion swims via strong strokes, and crawls and clings to water plants. When at rest, they slyly hide upside-down amongst the vegetation, letting their breathing tube out of the water to catch atmospheric air. They track their prey furtively, approaching the fry of insect larvae with considerably slow, almost inconspicuous movements. As soon as the unaware prey is within some millimetres, the Water scorpion swiftly embraces its victim with its raptorial front legs. 

© Chris Martin Bahr / WWF


#23 Axolotl

The Axolotl, Ambystoma mexicanum, is a rare and intriguing species endemic to Mexico and one of the few fully aquatic salamanders in the world. They have a deep-rooted cultural significance in the region, but nowadays are found exclusively in Lake Xochimilco, near Mexico City. Their funny-looking (and charismatic) appearance is due to a unique characteristic known as neoteny – the retention of juvenile features, such as external gills, despite reaching sexual maturity. Presenting an astonishing and one-of-a-kind ability to regenerate body organs and lost limbs, Axolotls are on the spotlight of cellular regeneration research – they can even receive transplanted organs from other individuals and accept them without rejection. Sadly, this extraordinary species is listed as Critically Endangered on the IUCN Red List of Threatened Species mainly due to two factors: poor water quality and the introduction of non-native fish species, especially the Oreochromis niloticus (Tilapia) through competition and predation. Within conservation efforts, the work of the Sisters of Immaculate Health stands out – they are skilful Axolotl breeders! To save one of the world’s most endangered and most remarkable amphibians, the amazing nuns partnered with conservationists from Chester Zoo (find out more about their work here).

© Muhammad Zaid Nasir / WWF Malaysia


#21 Painted terrapin

The striking Painted terrapin, Batagur borneoensis, is a freshwater turtle native to Brunei Darussalam, Indonesia, Malaysia, and Thailand. They present plain grey skin and shell for most of the time, letting their beautiful colours only pop during the mating season from January to June. The males are the ones to go through the transformation and “paint” themselves – their carapace lightens in colour to showcase striking black markings, and their heads turn to pure white with a bright red strip between their eyes. The female terrapins nest in beaches, but instead of the new-borns (a.k.a hatchlings) heading to the open ocean like their sea-going “cousins”, they make their way towards fresh and brackish waters. After reaching their mating age, pregnant Painted terrapins return to the same beach where they once hatched to lay their own eggs - the circle of life! This predictable behaviour, however, is one of the reasons this species is listed as Critically Endangered on the IUCN Red List of Threatened Species – it makes them vulnerable to habitat destruction and poachers who steal the eggs to eat or sell. Learn more about this incredible species and WWF conservation efforts with this great read.

© Pr. George F. Turner, IUCN


#20 Chambo

Endemic to Lake Malawi in East Africa, the Chambo, Oreochromis karongae, likes to swim around in loose shoals. Like other fishes of the Oreochromis genus, they present a curious form of parental care called maternal mouthbrooding. During spawning, soon after the male has fertilized the eggs, the mother puts them in her mouth until they hatch – a fascinating strategy to protect their offspring. The Chambo is also very important for local subsistence and commerce, being the most valuable food fish in Malawi. For this reason, they are threatened by overfishing. In the 1990s, the populations of the Chambo collapsed, with a 70% decline within ten years  –  unsurprisingly ending up listed as Critically Endangered by the IUCN Red List of Threatened Species. 

© Barry Warrington


#22 Flatworm

The flatworm, Crenobia alpina, is not your typical freshwater star species. With two primitive eyespots giving them a charismatic look, this species can grow up to 15mm in length (take a look at them moving here). This harmless flatworm is a predator found most frequently in cold and clear mountain streams. Their preference for cold waters comes with a price in a climate-changing world – a 40-year study shows that this species (as well as other invertebrates) has vanished from Llyn Brianne and much of Wales when the temperature of the streams rose. As the professor of ecology at Cardiff University’s school of biosciences, Steve Ormerod says, “the loss of freshwater organisms is a hidden tragedy, and it’s amazing how much is left to discover”.

© Myron Tay


#19 Spoon-billed sandpiper

The Spoon-billed sandpiper, Calidris pygmaea, is a petite wading bird with a unique spatula-shaped bill.  With their heads down in shallow and wet meadows, they move their bills side to side to look for food, also using it sometimes as a shovel. This migratory bird has a very specialised breeding habitat found in north-eastern Russia – lagoon spits where they can nest among crowberry plants, dwarf birch, and willow sedges with adjacent estuary or mudflats. During winter, they migrate down the Pacific coast to Southeast Asia – relying heavily on intertidal areas of the Yellow Sea along the way. Unfortunately, their stopover habitats, as well as their breeding and wintering grounds, are being degraded, resulting in the Spoon-billed sandpiper being one of the world’s most endangered birds. They are listed as Critically Endangered by the IUCN Red List of Threatened Species. As a response, the Spoon-billed sandpiper is one of the priority species of our Asian Flyways initiative, which aims to restore and protect an international network of wetlands used by this and other migratory birds populations.

© Jan Hamrsky


#18 Freshwater jellyfish

Did you know that jellyfish also exist in freshwater systems? Native to the Yangtze River valley in China, the Freshwater jellyfish, Craspedacusta sowerbii, prefers to live in still or slow-moving water bodies such as ponds, reservoirs, quarries, and lakes. Similarly to other jellyfish, they have a complex life cycle that generally includes 5 moments:  microscopic podocytes (dormant "resting bodies"), two different larvae phases, polyp phase, and the most recognizable (but least common in the environment) – the hydromedusa (right picture). As opportunistic predators, the Freshwater jellyfish feeds on small organisms that come within its reach, capturing their prey with the (in)famous stingers. But there’s no need to worry next time you take a dip in a lake - the stinging cells are so small that they usually don’t hurt vertebrates.

© Peter Chadwick / WWF


#17 Lesser Flamingo

This week we celebrate the exquisite and outstanding Lesser flamingo, Phoenicopterus minor. This species is “lesser” only in the sense that it is the smallest of the six species of the flamingo family. They have the biggest population of all flamingos, with two to three million individuals. They are also tolerant to extreme environments – their habitat is hostile for many animals and plants due to high temperatures, salinity, and alkalinity, but the Lesser flamingos are superbly adapted. Living around lagoons or lakes of Africa and India, they walk through shallow waters with their thin, pink legs as they feed - bending their necks downward to filter their food. It is thanks to their diet - rich in carotenoid pigments - that their feathers become remarkably pinkish. The bright pink colouration may function as a signal of parental capability, attracting mating partners – as parents take turns in brooding, one of them needs to look for food efficiently. The Lesser flamingo also shines with their spectacular courtship dance: groups of more than 1000 birds march together with a straight-up posture like soldiers, moving their heads and necks synchronously. These extraordinarily social birds also synchronize other activities such as brooding, to “crowd-protect” their offspring. A recent study even suggests that they form lifelong friendships – making it impossible not to fall for the flamboyant flamingo.

© Barthlott, Univ. Bonn


#16 The Waterwheel plant

The Waterwheel plant, Aldrovanda vesiculosa, might seem harmless with its tiny and delicate appearance while free-floating its “rootless-self” in peat-bog pools, lakes, and river deltas. Especially for an unsuspecting small aquatic invertebrate, who gets unwittingly too close to the Waterwheel and…SNAP! It is trapped in their prey-catching leaves. This remarkable and rare carnivorous aquatic plant has a snap-trap system that can be set off inadvertently by their game - the prey stimulates, mechanically, trigger hairs found in the central region of the trap leaves, prompting the two trap lobes to rapidly (as short as ten milliseconds!) move toward each other. Sadly, this unique species is listed as Endangered by the IUCN Red List of Threatened Species, known in only 50 isolated populations across the globe. The Waterwheel plant faces many threats, including eutrophication and degradation of its wetland habitat, driven by unsustainable agriculture and development. 

© naturepl.com / Roland Seitre / WWF


#15 Irrawaddy river dolphin

To celebrate Dolphin Day (April 14th), we present to you the charming Irrawaddy river dolphin, Orcaella brevirostris. With a rounded head and no beak, the three subpopulations of this distinctive dolphin can be found swimming along three rivers in South and Southeast Asia - Ayeyarwady River (Myanmar), Mahakam (Indonesia) and Mekong (Cambodia). Recent estimates indicate that there are around 79 individuals left on the Ayeyarwady, indicating this is a species right on the edge. Nonetheless, less than 300 freshwater Irrawaddy dolphins still live, including in Cambodia and Indonesia. Although they are not directly exploited, these river dolphins suffer many threats, including entanglement in gill nets and illegal fishing activities such as electrofishing - which unsustainably removes their food source. Nevertheless, fishing activities can be done in harmony with river dolphins. In the Ayeyarwady river, the local fisherfolk use a traditional fishing method that portrays a unique relationship with the dolphins, called “Cooperative fishing”. The fishermen “call” the dolphins by tapping a stick repeatedly on the side of the boat. If the dolphins are up to fishing, they chase shoals of fish towards the waiting nets and signalize the location of the prey. Once the fishermen cast their nets, the dolphins snatch the escaping fish. As this extraordinary interaction can be seen only in a few places around the world, many initiatives – such as our River Dolphin Rivers - work on the conservation of both the Irrawaddy dolphin and the fishermen’s way of life.  


© Arthur D. Chapman


#14 Surinam toad

The Surinam toad, Pipa pipa, is a fully aquatic amphibian known for its unusual appearance and fascinating – some might argue horrifying - parental care adaptations. You can find this species mostly in the slow-flowing waters of the Amazon Basin in South America, generally hiding under submerged leaf-litter - with their extremely flattened body and triangular-shaped head, they blend in for looking like a mottled brown leaf. This species also exhibits a unique courtship behaviour: after attracting a mate by making clicking sounds, the male toad mounts onto the back of the larger female and embraces her around the waist - if she is receptive, their mating act starts, and the pair displays some aquatic somersaults that can last for more than 12 hours. With the help of the male, the fertilized eggs are rolled up onto the back of the now upside-down female – the eggs sink into the puffy and swollen skin and are almost completely enveloped by it. The pregnant toad carries the developing offspring for three to five months until the “toadlets” are ready to punch their way out of their mother’s skin pockets, in a bizarre scene that can make many people shiver.

© Jan Hamrsky


#13 Net-spinning caddis

The Net-spinning caddis, Hydropsyche siltalai, is a species of Caddisfly; insects that are aquatic as larvae. They spend up to a year in lakes and rivers around the world before emerging as adults - and graduated engineers. One might think that larvae can’t be up to much, but the Net-spinning caddis larvae are quite busy building their retreat - a fascinating dreamcatcher-like silk structure. The larvae produce silk threads and weave it into fine-meshed nets that filter food particles from the water column while sheltering them. Recently, scientists found that these silk structures might influence local hydraulics – they can reduce flow downstream by 95% and upstream by 17%, besides altering turbulence (for more information, check the scientific paper). Even though the impressive caddis larvae seem to be well prepared to face the world and reach adulthood, recent research showed that they are in sharp decline - vulnerable to changes in climate.

© Johannes Sipponen / WWF


#12 Arctic char

World Water Day was on March 22nd, and to celebrate our most precious resource, we introduce you to the northernmost freshwater fish in the world: the beautiful Arctic char, Salvelinus alpinus. These circumpolar fish species inhabit cold and clean waters around the North Pole. Numerous local freshwater populations of Arctic char exist in all Arctic states, plus a smaller number of sea-run populations - where fish can grow up to 10kg in weight. The Arctic char suffers from increasing temperatures due to climate change, especially the more southern populations in the Alpine regions, which can be at risk of extinction - water temperature and quality are significant factors in the survival of their sensitive eggs. According to the first report on The State of the Arctic Freshwater Biodiversity (2019), climate warming increasingly threatens freshwater biodiversity in arctic lakes, rivers, and wetlands. The report also suggests that the Arctic char – as well as other cold-water species endemic  to the Arctic – are likely to suffer regional losses, or even local extinctions as a result (find out more with this great article). Similarly, the 2019 report of the Intergovernmental Panel on Climate Change (IPCC) states that changes in the cryosphere will alter freshwater communities - range shrinkage and extinction of some species can cause regional biodiversity to decrease. WWF Finland has been involved in a conservation project to strengthen the population of Critically Endangered Lake Saimaa Arctic char. Also good news exists: exploitation of the northern Arctic char population in Finland has decreased at the same time with improved protection, leading to improved conservation status in the Red Book of Species for Finland –  bending the curve in freshwater species does exist!

© Ryan Francis


#11 Tasmanian Giant freshwater crayfish

In the rivers and streams of Tasmania lives the world’s largest freshwater invertebrate – the endemic Giant freshwater crayfish, Astacopsis gouldi. The IUCN Red List of Threatened Species list this species as Endangered, mainly as a result of years of past overfishing, illegal fishing, and habitat loss and degradation. Capable of reaching 6kg in weight, they have been harvested as a food source at a local and national level. The effects of fishing pressure are aggravated by their biological characteristics -  this menacing-looking giant is actually very easy to catch, besides being slow-growing with low breeding potential. This species has received attention as a species of conservation concern - in the 90s, the Australian and Tasmanian governments added the Giant freshwater crayfish to their environmental legislation, and, recently, the critical habitat has been redefined. 

© Andre Dib / WWF Brasil


#10 Victoria water lily

A long time ago, a young warrior called Naiá, from a Brazilian Amazonian tribe – “Tupi-guarani”– would dream about the day she would meet with Jaci, the moon. According to the legend, Jaci was a goddess who every night would kiss the most beautiful women of the tribe, and before hiding behind the mountains, she would pick her favourite to transform the woman into a star. Every night, Naiá would walk around the hills searching for Jaci. One day, after seeing the reflection of Jaci on a lake, she threw herself inside the lake and drowned. The moon compassionately decided to reward Naiá for her sacrifice, transforming her into a star of the waters – the Victoria water lily, whose white flower only opens at night and changes to pink when the sun rises. 
The myth of the Victoria water lily above is a fragment of the memory of WWF's Paula Martinelli, who remembers hearing this story growing up in Brazil. The Victoria water lily, Victoria amazonica, is native to the Amazon biome and the symbol of the Amazon state of Brazil. The legend of the Victoria water lily has some truth to it – the white flowers only bloom at night, its colour changing to pink or ruby red after spending the evening exuding a strong odour to attract beetles to pollinate them. The flower closes its petals in the morning, hopefully trapping the beetles and releasing pollen on them. They open again in the following evening, releasing the beetles to transport their pollen to other flowers – they now have different colours and are scentless, being less attractive to the beetles. This fascinating adaptation avoids fertilization by its own pollen, increasing the genetic variability of the world’s largest water lily. 

© WWF/Jiri Bohdal


#9 Beluga Sturgeon

To celebrate World Wildlife Day (tomorrow on March 3rd), this week we present to you the majestic Beluga sturgeon! Even though there is still a debate on which is the largest freshwater fish in the world, the Beluga sturgeon, Huso huso, is undoubtedly the largest migrating freshwater fish – with a record of 1,571 kg and 7.2 m, this female was caught in 1827 in the Volga estuary. But this is history -  nowadays, you can seldom observe a length above 2m. This species has been recorded swimming in the basins of the Caspian, Black, Azov, and Adriatic Seas. The migration of the Beluga sturgeon was predictable, and as a huge fish, they were an easy target, providing abundant food for many people. Its current native wild distribution is restricted to the Black Sea (Danube and Rioni) and the Caspian Sea (Ural). It does occur in the Azov Sea and Volga River, but as stocked fish. Due to historically severe overfishing and poaching in estuaries and rivers, the Beluga sturgeon is listed as Critically Endangered (CE) by the IUCN Red List of Threatened Species. This species is wanted for its meat and caviar - one of the most valuable products on the food market. Their caviar is considered top class caviar and is among the most expensive – you can buy 30g in London at the modest price of €420, which adds up to a price of €14.000 per kg. The beluga sturgeons’ eggs can only be legally obtained from aquaculture. Unfortunately, illegal wild caviar is still in demand on the black market by customers who consider "wild" as the "real" thing. IUCN also states that sturgeons are more critically endangered than any other group of species – 23 of all 27 known species are considered to be threatened with extinction. The mighty Beluga sturgeon can live for over 100 years, spending several years in the sea and migrating longer distances than any other sturgeon – more than 1000km. Because of their particular long life cycle, the recovery of its heavily depleted stocks will need several decades. But they can still be saved. WWF is working together with communities, civil society, companies, scientists, law enforcement authorities and governments across the world to rebuild their population. For example, our Sturgeon initiative is tackling the illegal caviar trade and enhancing the health of river systems. And, last year, WWF helped to save a Beluga in the Danube.

© Zeb Hogan WWF


#8 Giant freshwater stingray

The Giant freshwater stingray, Urogymnus polylepis, is one of the largest and heaviest freshwater fishes in the world. With the ability to gain more than 600kg and 2m disc width, this freshwater giant mostly swims the large rivers of south and southeast Asia ( find out more about the beautiful Giant stingray and other giants of the Mekong river in this report). The IUCN Red List of Threatened Species lists the Giant freshwater stingray as Endangered, mainly due to fisheries and habitat degradation. The development of dams is also one of the drivers for their – and other freshwater megafauna species – population declines. Among WWF’s conservation efforts is our Resilient Asian Deltas (RAD) Initiative, whose ambition is to secure healthy and functioning river systems from source to delta through unprecedented political and financial investment in ‘building with nature’. To address the crisis facing freshwater biodiversity like the Giant freshwater stingray, WWF has just published an Emergency Recovery Plan  - together with scientists from across the world  - as a call to action to the world’s decision makers to value, protect and restore freshwater habitats before it’s too late.

© Martin Harvey / WWF


#7 Grey Crowned crane

The Grey Crowned crane, Balearica regulorum, calls attention for its beautiful colours and a majestic golden plumage on their head unfolding like a crown. They are also known for displaying playful behaviours such as dancing. Mainly a form of socialization and pair formation, other species of cranes are also famous for their dance moves. You can find the Grey Crowned crane “performing” in the eastern and southern regions of Africa, where they are also a culturally important species – considered icons of Africa’s wetlands and savannahs, besides being the national bird of Uganda. However, it’s not all glamour for the Grey Crowned crane. Listed as Endangered by the IUCN list of threatened species, they are threatened primarily by illegal trade, disturbance, and habitat loss. The Global Wetland Outlook 2018 states that up to 87% of wetlands have been lost since 1700. The Grey Crowned crane and the other 14 living species of cranes need wetlands as stepping stone corridors –  where they can find a safe harbour to sleep, rest, nesting, and rearing the young. As cranes are among the most threatened bird families in the world, WWF has joined the International Year of Crane 2020, announced by the International Crane Foundation and the Crane Working Group of Eurasia. The Amur River basin is the flyway and breeding grounds of no less than six species of cranes, and WWF will be working with partners in the region to strengthen the conservation of both wetlands and the majestic cranes.

© naturepl.com Visual Unlimited WWF


#3 Hellbender Salamander

The Hellbender salamander, Cryptobranchus alleganiensis, a.k.a. giant salamander, is, non-surprisingly, the largest salamander in North America – and the third-largest in the world. But these amphibian giants are fascinating not only for their size: they have lungs, but they mostly breathe through their wrinkly skin; they can swim, but usually walk underwater through their sturdy limbs. With tiny eyes on the top of their heads and light-sensitive cells all over their bodies, especially on their tails, they can keep their (giant) selves completely hidden from large fish under rocks and use their keen sense of smell to hunt crayfish. Besides playing this important role in their ecosystem, they are also bioindicators of stream quality, as they have a low tolerance for poor water quality. It is not a good sign for the North American rivers that their populations are considered Near Threatened by the International Union for Nature Conservation (IUCN), mainly due to the worsening condition of their freshwater habitats. Find out more about this species in this cool video by David Herasmtschuk.

© Tim Lane


#6 Rainbow mussel

The Rainbow mussel, Villosa iris, is a fascinating freshwater species not only for its beautiful inside shell, which is iridescent – they are also the master of disguise! “Hidden” in the North American rivers and streams, this tiny mussel uses mimicry to increase its odds of success: the mussel lures fishes by looking and moving like a crayfish, which is, in reality, a few flaps of fleshy skin coming out of its shell. Once the fish is close enough to take a bite of the “crayfish”, the Rainbow mussel releases a cloud of tens of thousands of parasitic spawn! Aiming for a safe place to transition into juvenile mussels, the mussel larvae latch to the fish’s gills, fins, and skin. Their new “home” (and “ride”) also provide for their food – they feed on the minuscule amounts of nutrients from their host. Most of the time, however, the fooled host-fish is not harmed by this interaction. 

© Justin Jin WWF US


#4 Yangtze Finless porpoise

The Yangtze Finless porpoise, Neophocaena asiaeorientalis asiaeorientalis, as the name suggests, lives in the Yangtze River and is the world’s only freshwater porpoise – and one of only five surviving species of freshwater cetacean. Unfortunately, there are only an estimated 1,012 finless porpoises left in China’s greatest river and they are listed as Critically Endangered on the IUCN red list of threatened species due to a host of threats, including water pollution, overfishing, boat traffic, sand mining, and river fragmentation. Many finless porpoises have also been killed after becoming accidentally entangled in gill nets – something which contributed to the extinction of the Yangtze freshwater dolphin, the Baiji (Lipotes vexillifer). But there is still hope for the Yangtze finless porpoise. Led by the Chinese government, conservation efforts – involving WWF, partners and local communities – have helped to drastically slow the annual decline in the finless porpoise population, including relocating animals to safer habitats away from the river’s mainstem to create new breeding populations. Huge amounts of work still need to be done to secure the survival of the species and WWF will continue to be at the forefront through its global River Dolphin Rivers initiative. This initiative is working on the development of smart river pingers in an effort to prevent future entanglement in gillnets. For many years, the finless porpoise had little to smile about but thanks to the combined efforts of the government, communities and conservationists, there is now a chance that the species can turn the corner and that its population will finally start to increase.

© WWF India


#5 Golden Mahseer

The Golden Mahseer, Tor putitora, is one of the world’s most iconic freshwater fish – highly prized by anglers, it is viewed as a God fish by local communities in some parts of South Asia, such as India and Bhutan. But its numbers are declining across South and South East Asia due to a range of threats from dam blocking its migratory routes to pollution and unsustainable fishing. It is now classified as Endangered on the IUCN Red List of threatened species. Local communities in India have revered fish species as symbols of divine power, offering them protection and building temple sanctuaries along the river banks, the first established nearly 1200 years ago. The Golden Mahseer benefits from this protection in several stretches of the river Ganges associated with these temples, where fishing is not allowed, and local communities, pilgrims, and temple authorities help to monitor and protect the mahseer population. The Mahseer also has cultural, religious and economic significance in Bhutan, where it is known as the Tiger of the River (you can find out more in this great documentary on the “Tiger of the River” produced by WWF Bhutan). In 2015, as a response to the pressures on Bhutan’s river systems, the Fisheries Conservation Foundation, WWF Bhutan, and the Ministry of Agriculture and Forests started a partnership to assess the migration pattern of the God fish using radio telemetry technology. This year, the 2nd International Mahseer Conference  is being held in Thailand from 11th to 15th February, where researchers and conservationists - including WWF - will share knowledge, collaborate and promote the conservation of the species.

© Meridith Kohut WWF-US


#2 Matamata turtle

The matamata turtle, Chelus fimbriata, is one of the world’s largest freshwater turtles – and undeniably one of the weirdest too. Found in the Amazon and Orinoco basins, their unmistakable appearance is the combination of a leaf-shaped head, a long pointy snout, a rough tuberculate flat shell, and an elongated, thick neck with protuberances. The bizarre look is the result of a unique adaptation for feeding and blending in - they are incredibly specialized feeders that wait for dinner to come to them. When unknowing fish approach them to see if the protuberances on their neck are edible, they quickly stretch their neck out and open their mouth to create a vacuum that swallows their prey whole.

© Tim Watt


#1 European eel

For the first week we are highlighting the European eel, Anguilla anguilla. There can be few species more mysterious than the European eel, Anguilla Anguilla. A species that breeds just once in its lifetime and must travel thousands of kilometres to do so. European eels, like other Anguillid eels exhibit a number of life stages: they start their lives in the ocean as leptocephalus (larvae) which float back to estuaries where they turn into glass eels, and then elvers before travelling upstream into our rivers where they turn into yellow eels. The final stage of an European eel’s life is as a silver eel; silver eels are able to migrate thousands of kilometres to the Sargasso sea to spawn. No one has witnessed their spawning and so the spawning location remains a hypothesis. European eels are a Critically Endangered species, threatened by dams and infrastructure, habitat destruction and illegal trafficking. Find out more about this enigmatic and mysterious freshwater species in this great article.
If you’d like to find out about other Anguillid species, check out this blog from Kathy Hughes, our very own Freshwater Habitats and Species ACAI lead. Kathy like’s eels so much she takes holidays especially to swim with them.

© Tim Watt

© Tim Watt