Structure and production of fish communities in tropical rain forest streams of northern Borneo

Tropical fish communities are often assumed to be more productive than temperate communities. To test this belief, fishes from tributaries of the tropical rain forest Baram River, Sarawak, Malaysia were quantitatively collected with a piscicide and production was calculated by the Ricker algebraic method. Temperature was not considered a major factor influencing production among different climatic regions since the average production in the Baram (76.7 kg∙ha−1∙year−1) was less than in temperate Grand River, Ontario (279.4 kg∙ha−1∙year−1) and Nida River, Poland (121.0 kg∙ha−1∙year−1). Analysis of physical habitat characteristics, community-structure variables, and production estimates from Baram streams indicated production was controlled mainly by nutrient limitations (P < 0.01) while close species packing maximized production by efficiently utilizing the limited resources available. In highly competitive and diverse communities, Baram fishes have probably developed specializations which make them particularly vulnerable to environmental perturbations or overexploitation. An estimated fish catch of 14.2–19.6 kg∙ha−1∙year−1 by Baram subsistence fishermen was already within the estimated range for maximum sustainable yield (7.9–20.9 kg∙ha−1∙year−1). Therefore, it is recommended that research on community ecology should precede expansion of artisanal fisheries.