Assessment of aquatic biodiversity in relation to environmental parameters in Gawha beel, Nawabganj, Bangladesh

A study was conducted to find out the aquatic biodiversity in relation to the environmental parameters in Gawha beel (floodplain wetland), Bangladesh. The approximate water area during rainy season was 500 ha and that during dry season was 45 ha. A total of 38 freshwater finfish and shellfishes belonged to six orders, 18 families and 28 genera were identified in the Gawha beel. Out of total 38 species, 37 were finfish species (32 indigenous and 5 exotic species) and remaining one shellfish (prawn). Parambassis nama and Oreochromis mossambicus were found to be the dominant fish in numerical and weight abundance, respectively. Salomostoma acinaces (22.32%) and Gudusia chapra (23.39%) were found to be the abundant migratory fish fauna in terms of numerical (%) and biomass (%) abundance, respectively. Altogether 38 genera of plankton were recorded of which 29 genera representing phytoplankton while zooplankton represented 9 genera. Beel showed considerably higher phytoplankton diversity than its zooplankton diversity. Quantitative abundance of plankton were found to fluctuate from 383 to 5267 cells/l during study. Plankton population was significantly correlated with different water quality parameters. A total of 22 genera of macrobenthos belonged to 12 families were recorded in the beel. Out of 22 genera, Mollusca was dominated with 10 genera followed by Diptera (8 genera) and Oligochaeta with four genera. Diptera (48%) were found to be the most abundant macrobenthos in respect to quantitative abundance. Macrobenthic fauna was highly (P<0.01) correlated with diptera. Oligochaeta represented a strong and significant relationship with sediment pH. Environmental parameters showed significant relationship within different parameters but it varied in respect to season of the beel. The findings of this study are expected to provide baseline information on fish, plankton and macrobenthos biodiversity in the beels for sustainable use of beel fisheries resources.