Freshwater molluscan assemblages in upper part of Choen River Basin, Northeastern Thailand

Abstract

Freshwater molluscan assemblages were studied from the upper part of the Choen River Basin, Northeastern Thailand. Ten plots of 1x1 m2 were used to collect specimens from 10 stations in the dry season from June to July 2015. In total, 5,394 specimens belonging to seven families, 14 genera and 18 taxa of gastropods and two families, five genera and six taxa of bivalves were found. The species with the highest abundance was Filopaludina (Siamopaludina) martensi martensi (1,568 specimens or 29.07%) and the species with the lowest abundance were Pila polita, Corbicula lamarckiana, Trapezoideus exolescens comptus and Cristaria plicata (one specimen for each species 0.02%). Ecological statistics were also analyzed, which comprised of density = 53.94 individuals/m2, Shannon-Weiner diversity index (H') = 2.27, Fisher's alpha (α) = 3.23, and similarity index (SI) among each station ranging from 0 - 67.12. Based on cluster analysis and canonical correspondence analysis (CCA), each species was related to environmental parameters, including velocity, dissolved oxygen, water temperature, electric conductivity and total dissolved solids. It was possible to divide the freshwater molluscs of the upper part of the Choen River Basin into two assemblages, i.e. Brotia (Brotia) baccata - Corbicula blandiana assemblage, which was found from a sand-gravel base stream with rapid current, and Filopaludina (Siamopaludina) martensi martensi - Pilsbryoconcha exilis compressa assemblage, which was found from a clay base stream or river with stagnant or slow current.