The upper Pelus River is located in the remote area of the Kuala Kangsar district,
Perak, Malaysia. Recently, the forest along the upper portion of the Pelus River has
come under threat due to extensive lumbering and land clearing for plantations. Sampling
at 3 localities in the upper Pelus River at 457, 156 and 89 m above mean sea level
yielded 521 specimens representing 4 orders, 11 families, 23 genera and 26 species.
The most abundant species was Neolissochilus hexagonolepis, followed by Homalopteroides
tweediei and Glyptothorax major. The fish community structure indices was observed
to increase from the upper to lower portion of the river, which might reflect differences
in water velocity.