Ichthyofaunal integrity, hydrological and environmental features trade-off in the Sunderbans, India

Herein, we studied the ichthyofaunal diversity of the Bidyadhari River in the Indian Sundarbans for three consecutive months (April 2018-June 2018). The fishes in this study were captured and collected from two collecting stations (points) using bag nets operated by local fishers. We determined Simpson’s index of diversity (1-D), Shannon-Wiener’s index (H) and the coefficient of community (CC) to find out the species richness, abundance, evenness and the levels of similarity between the two collection points. We converted the H values to true diversities (effective number of species [ENS]) for an adequate comparison. The indices and coefficient (H = 3.72-4.05, 1-D = 0.96-0.97 and CC = 0.87) indicate that the overall integrity of biodiversity of the two collecting points is moderately high. From the true diversity values, we conclude that the first collecting point is 1.39 times as diverse as the second one. It is attributed to a complex of abiotic and biotic factors that we talk about in the discussion part. We also recorded 19 species of fishes which are new reports for the Indian Sundarbans and discuss the possible reasons for their occurrence.