Seasonal changes in fish assemblages and trophic guilds in selected interconnected rivers in eastern India

Abstract

The study aimed to assess seasonal changes in species diversity and trophic guilds in selected connected rivers in eastern sub-Himalayan India. The environmental influence was reflected in seasonal differences in the fish assemblages over five main climatic seasons. Diversity estimators indicated that species richness and evenness were greater in the monsoon and autumn as was overall species diversity. Dominance-diversity measures also showed greater richness and evenness of fish species during monsoon and autumn, and overall diversity was reduced concomitantly with increase in species dominance in the later months. From the Canonical Correspondence Analysis (CCA), it could be concluded that dissolved O2, CO2, temperature and nutrients were the most significant determinants of species assemblages in these tropical rivers. Fish samples were categorised into seven trophic guilds. The fish community was dominated by planktivores during monsoon and plankti-detrivores in other seasons. Assessments of the conservation status of the available fish species indicated that most species encountered during the monsoon and autumn were threatened. Since these rivers provide important refuge for a number of species due to their shallowness, varied trophic niches and suitability as a reproductive site, this study suggests a community level conservation approach considering the seasonal impacts to integrate with the population specific conservation programmes.