Depauperate freshwater fish communities in Sabah: the role of barriers to movement and habitat quality

• Published in: Journal of fish biology 1998-12, Vol.53 (A), p.331-344
• Main Authors: Martin-Smith, K M, Laird, L M
• Format: Article
• Language: English
• Subjects: Malaysia, Sabah; Sabah
• ISSN: 0022-1112
• DOI: 10.1006/jfbi.1998.0801

Up to 30 species of fish were generally found in medium-sized rainforest streams in Sabah, Malaysia. However, depauperate fish communities were found in two streams above large (>8 m) waterfalls (five and nine species) and in two very small streams located in deep forest (five and six species). A fifth stream with small cascades and waterfalls had a faunal list of 12 species. Species resident above waterfalls were predominantly herbivores while fishes in the two forest streams were from a variety of trophic groups. Abundance and biomass of fishes above waterfalls were significantly lower than all other sites. A translocation experiment was performed in one stream to distinguish between the hypotheses that fish communities above waterfalls were determined solely by colonization ability and were unsaturated with species or that they were limited by habitat quality or food. Seven species (775 individuals) were translocated into one isolated section and four species (570 individuals) into another. Species that were translocated included trophic groups that were not represented by resident species. Twelve months after translocation, only four and one translocated species were collected in the two sections, all at greatly reduced densities. After 20 months, the number of species were three and two, respectively. One translocated species, Rasbora sumatrana, had increased in abundance from 12 months and juveniles were present in the population. Individuals of other translocated species appeared to be remnants of stocked populations. Abundance and biomass of resident species fluctuated widely between years. Interpretation of results was complicated by a large flood which substantially changed habitat conditions about a month after translocations were performed. It is suggested that two different factors were responsible for depauperate communities: movement barriers for waterfall sites and physico-chemical conditions and/or habitat availability at other sites.