Siluriform Fishes and their Habitat in Small Rivers in Central Thailand

Abstract

Silurids were sampled, by electrofishing, from 159 sites on small rivers in four major watersheds across central Thailand, Eastern, Chao Phraya, Peninsula and Maeklong. Total abundance, estimated by the depletion method, was low across all sites at under 3% of all fishes and varied directly with water velocity, dissolved oxygen, iron and pH and, inversely with turbidity. Species richness was highest in Maeklong watershed and, across all watersheds, varied directly with ambient oxygen, iron and pH and inversely with turbidity. Incidence of occurrence was not high for any species within any but the lightly sampled Eastern watershed and no species was captured across all watersheds. Canonical correspondence analysis was applied and identified three significant habitat variables, temperature, conductivity and ambient oxygen, and the extent to which each influenced the distribution of the 17 silurid species. The results are discussed in relation to environmental factors and ecology.