Borneo freshwater fishes
Borneo’s silent waterworld
Walking fish?This peculiar family includes the forest walking catfishes, as some species are capable of travelling over short distances on land. Owing to their ability to survive out of the 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.
More than 3 species discovered every month during the past 15 years
Needs and lifestyles of Borneo’s freshwater fishesSome freshwater fish have adapted to very specific habitats. For example, Waandersii's hard-lipped barb (Osteochilus hasseltii) inhabits 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 areas adjacent to rivers that have become flooded.
Conversely, 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 discern in its habitat, where it lies among the leaf litter and plant detritus.
Borneo also has its own bonytongue 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 feng shui, large specimens can fetch up to US$20,000 and wild populations are severely threatened by habitat degradation and the aquarium trade.
- Clarias insolitus, first described from the Barito River drainage in Central Kalimantan (Indonesian Borneo).
- 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), fishes 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 zebra-striped fish
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. The water in this habitat type is often murky, with substrate composed of mud or fallen leaves, twigs and branches.
Such environments are also often dimly-lit due to the rainforest canopy above. The fish were found sheltering among overhanging tree roots and aquatic vegetation. It is noted as something of a shy, reluctant feeder.