21st of November: Celebrating fish and the strange species of Sebangau

Research Blog

by Sara Thornton

Today fishing communities around the world celebrate World Fisheries day to highlight the importance of maintaining the world’s fisheries and the rivers, lakes and oceans that sustains them. It is also Indonesia’s National Fish Day – so even more reason for us at BNF to celebrate!

Across Kalimantan (Indonesian Borneo) fishing is one of the main sources of livelihood and protein for many of the communities living alongside rivers and wetland habitats such as peat-swamp forests. Because the water in peat-swamps are very acidic and have low oxygen levels (as there is a lot of standing water), these forests are also habitats to unique fish species that are specially adapted to live in these tough conditions. There hasn’t been much research done on these peat-swamp fish species and their importance for local communities, which is why we tackled this gap with BNF for my PhD at the University of Leicester. In our fish surveys in the Sebangau river and forest it was exciting to find 55 different species of fish (see our recent publication: Thornton et al., 2018)! This includes some strange and special species, like the ones pictured below (I have added facts about each one).

Four unique Sebangau fish species signature to peat-swamp river
Photo by Gustav Eek & Sara Thornton | BNF | CIMTROP

  • A: Chaca bankanensis or the Angler catfish (called ‘Tabengkung’ locally): what a surprise it was to find this strange looking fish in my trap! It can use its barbels as a kind of lure, using them to simulate the movements of a worm when potential prey approaches. They eat fish and shrimp, and can swallow prey almost as big as itself. It can grow to about 20 cm long, and has a short dorsal spine that can inflict a painful wound – so watch out!
  • B: Betta hendra, one of the betta species, and it is only known to be found in the Sebangau forest! These are also specially adapted for life in the peat-swamp, with special breathing organs known as a labyrinth. This allows the fish, to a certain extent, to breathe atmospheric air!
  • C: Macrognathus maculatus, or the frecklefin eel (called ‘Jinjili’ locally). This is another one of my favourites, just look at that face! Their funny ‘nose’ is called a modified rostrum, which helps them to find and gather food (bottom-dwelling insect larvae, worms and crustaceans).
  • D: A species of Clarias, a walking catfish (called ‘Lele’ locally). These are common food fish in Indonesia and is another crazy fish adapted to living in the peat-swamp: it can also breathe atmospheric air, and is named for its ability to “walk” and wiggle across dry land to find food or suitable environments. Again, care has to be taken when handling these fish as it has an embedded sting hidden behind its fins. I can tell you from experience, it’s surprisingly painful!

Like many parts of the world, interviews that we conducted in villages in the Sebangau area indicate that communities are experiencing a decrease in fish populations. This has direct impacts on community livelihoods and their resilience to environmental change including climate change.

A family of fishers checks their catch on the Sebangau river
Photo by Sara Thornton | BNF | CIMTROP

These declines in fish populations are mainly because of habitat degradation from deforestation, increased fishing pressures from growing populations, river pollution and harmful fishing methods including poison and electricity. This of course threatens not only livelihoods but also the existence of species that are specially adapted and only found in peat-swamp forests and thereby the biodiversity of these vital areas.

For the river, fish and people: peat-swamp forests need to be conserved and degraded peatland areas need to be restored. Harmful fishing methods need to be stopped with alternatives found. All of this must be done in collaboration with communities so that together we can find solutions which are just and long-term.

Then, hopefully, we will be able to continue enjoying the amazing peatland fish and their vital habitats for generations to come!


Publication: Thornton, S.A., Dudin, Page, S.E., Upton, C. & Harrison, M.E. (2018): Peatland fish of Sebangau, Borneo: diversity, monitoring and conservation. Mires and Peat, 22(04), 1-25. (Online: http://www.mires-and-peat.net/pages/volumes/map22/map2204.php); 10.19189/MaP.2017.OMB.313