Fish diversity and assemblage patterns along the longitudinal gradient of a tropical river in the Indo-Burma hotspot region (Ping-Wang River Basin, Thailand)

Abstract

The relationships between environmental variables as descriptors to the fish community, in terms of species diversity indices, and the fish assemblage patterns along the longitudinal gradient in a rhitral environment of a large river system located in the Indo-Burma hot spot (Ping-Wang River Basin) were studied. Fish data and water quality parameters were collected between January 1996 and April 2009. The three most diverse families were Cyprinidae, Balitoridae, and Cobitidae, respectively. Three physicochemical parameters (i.e., DO, water temperature, and pH) and three geo-morphological parameters (i.e., altitude, distance from the sea, and discharge) showed statistically significant to diversity parameters (P value <0.05). The classification and regression trees showed that the geo-morphological parameters were more significant in predicting both species richness and Shannon diversity index than the physicochemical parameters, in which altitude was the most significant. Fish assemblages in the Ping-Wang River Basin were classified into four patterns viz., mountainous, piedmont, transitory, and lowland species.