One of the things that makes Gunung Palung so special is that it is a granite mountain, and erodes into coarse silica sand instead of mud. Consequently, the rivers run crystal clear in all but the heaviest floods. The riverscapes near our camp look especially gorgeous—cold, sparkling water splashes over rounded granite boulders, flowing between the red-barked Tristaniopsis whiteana (Myrtaceae) trees which line the sandier rivers in this part of Borneo.
Endro, a park staffer and one of two experienced parataxonomists at camp, brought a diving facemask, and I relished looking beneath the rushing waters. The fish diversity is not obviously high: perhaps only a few mid-water species and slightly more benthic feeding taxa among the rocks, including the flat-headed ‘Bornean sucker’ (aka ‘hillstream loach’, possibly Gastromyzon punctulatus Inger & Chin). What struck me most, however, was the behavior of a common, silvery cyprinid (carp family). In the lee of rocks and deeper pools, the fish would wait before darting out into the strong current after some passing insect or fruit morsel, reminiscent of trout I’d watched in the streams of the Sierra Nevada in California. Compounding this impression, I happen to know that these small fish will take a baited hook and put up a surprising fight.
The fish are known locally as ‘ikan semah,’ and their speed and agility are greatly valued by the ethnic Chinese population, who feed them to their young children to foster intelligence. The local price for a kilogram of fresh semah in nearby villages is Rp 250,000 (about $23), far more than any other fish. Given their abundance, the species represents a valuable and renewable resource. When I was able to get online again, I discovered that these fish are a type of mahseer, probably Tor douronensis, related to the fabled mahseer of India, which are admired for their sporting qualities.