Variations in abundance of fish larvae in Huai Jorakhe Mak reservoir (small wetland)

Abstract

Variations in abundance of fish larvae in small wetland (Huai Jorakhe Mak Reservoir) in Buriram Province, Thailand, were studied during July 2009 - June 2010. Samplings were conducted in 4 hydrological seasons in 12 stations within 3 zones (i.e. upstream, midstream and downstream). There were 15,870 larvae in 34 species and 18 families, which 14 species belong to Cyprinidae, and found throughout the study. The most three abundance species respectively were Rasbora spilocerca, Trichopsis schalleri and Parachela oxygastroides. There was no statistical difference of fish larvae species and abundance among the surveys (season * station). However, the species richness and abundance peaked in the upstream station during the dry season. Meanwhile, the lowest in species richness and abundance were observed in the midstream station during the transition of rainy to dry seasons and the downstream station during the dry season, respectively. Cluster analysis of species and abundance composition, resulted in 5 major clusters. Ordination study showed 4 dominant groups of larvae according their presences of the surveys and related to the water quality parameters and geomorphology characters during the surveys. Groups 1 and 2 were highly correlated with water quality parameters in particular to chlorophyll a and ammonium ion. Meanwhile, groups 3 and 4 were correlated with geomorphology characters as water level and inflow rate.