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Borneo’s waterworld

From the world-famous Asian arowana to obscure fishes that actually walk on the ground, Borneo's wildlife is equally amazing above and below the water.

© Dr Robert Clarke
Arowana, also known as dragon fish in Kalimantan. Although critically endangered, protection efforts within Kapuas Hulu, West Kalimantan, are seeing the population of this rare fish slowly increase
© Dr Robert Clarke
Some fish species, such as the catfish (order Siluriformes) show remarkable adaptations to their environment. For example, the labyrinth catfish family (Clariidae) is named after an organ arising from the species’ gills, which allows them to breathe atmospheric oxygen.

Borneo’s walking catfish

This peculiar family includes the forest walking catfishes, as some species are capable of travelling short distances on land. Able to survive out of water for extended periods, the walking catfishes are caught for food relatively easily and are subject to subsistence fishers and commercial farming operations.

Catfishes come in a range of colours and shapes. Species of the family Parakysidae are well camouflaged, hiding in small forest streams, and have wrinkly skin, branched barbells and a forked tail.

The family Bagridae are some of the largest catfishes in the world. They have conspicuous dorsal and pectoral spines, a distinct adipose fin (a small fin located behind the dorsal fin) and often deeply forked caudal (tail) fins.

Less conspicuous, the glass catfishes (family Schilbeidae), also known as ghost catfishes or phantom catfishes, are almost transparent, revealing their skeleton and internal organs.

Needs and lifestyles of Borneo’s freshwater fishes

Some freshwater fish have adapted to very specific habitats. For example, Waandersii's hard-lipped barb (Osteochilus hasseltii) live in clear, freshwater, tropical streams, with a preference for fast-flowing streams and rivers, where gravelly or stony substrate is available. When water levels rise, it moves into the flooded areas adjacent to rivers.

The spotted eel-loach (Pangio shelfordii), also known as the spotted coolie loach or Borneo loach, keeps to muddy, slow-flowing streams and pools in freshwater swamp forests. This orange fish, with a pattern of dark splashes, is difficult to see as it lies amongst the leaf litter and plant detritus.

Borneo also has its own bony-tongue fish (Scleropages formosus), also referred to as the Asian Arowana, which is confined to slow-flowing rivers and lakes.

Prized for the belief in its positive fengshui, large specimens can fetch up to US$20,000 and wild populations are severely threatened by habitat degradation and the aquarium trade.

On average, 3 new species are discovered each month in the Heart of Borneo

Between 1995 and 2010 over 600 species have been discovered - that is 3 species each and every month.


© Daisy Wowor
This new freshwater prawn species, Macrobrachium kelianense, was discovered in 2007. The species was one of two newly identified by scientists in the Kelian River, located in the interior of East Kalimantan, in the Heart of Borneo.
© Daisy Wowor

Fish discoveries in the Heart of Borneo

  • Clarias insolitus, a species of clariid (air breathing) catfish, first described from the Barito River drainage in Central Kalimantan (Indonesian Borneo). It differs from other Southeast Asian Clarias due to distinctive enlarged sensory canal pores on the head and body and a long and thin knife-shaped anterior fontanel (part of the skull). 

  • Clarias nigricans, identified by experts in Samarinda’s market, in East Kalimantan. This fish is thought to be a member of the ‘forest walking catfishes’, which are capable of walking short distances over the land.

  • Four new species of Asian banjos (Acrochordonichthys species), fish that display little activity and ambush their prey. The mucus they release when stressed is poisonous to other organisms, causing instant death to fishes in their vicinity.

  • A striking zebra-striped fish, Eirmotus insignis, was officially described in 2008. The eight-banded barb, as it is commonly-called, has been mostly recorded from the middle Kapuas, in the Heart of Borneo. One of 17 fish discovered in the Heart of Borneo in recent years, the eight-banded barb measures around 3.6cm, and typically inhabits slow-moving, shallow, shady rainforest streams and swamps.
© CK Yeo
A remarkably striking zebra-striped fish (Eirmotus insignis) was officially described in 2008. The eight-banded barb, as it is commonly-called, has been mostly recorded from the middle Kapuas between the towns of Sanggau and Putussibau, Kalimantan, in the Heart of Borneo.
© CK Yeo