Fish biodiversity and conservation status of the lower streams of the Dhepa river of Dinajpur, Bangladesh

The impacts of the establishment of fish sanctuary at the upstream of the Dhepa river in Birganj, Dinajpur, Bangladesh were investigated from January to December 2016. Monthly samples were collected from 3 sites of the river, the Kantonagor (25042’13.9”N; 88038’05.8”E), Karnai (25047’08.2”N; 88040’24.6”E) and Bangibacha ghat (25039’08.9”N; 88037’48.2”E). The collected fish were transferred to the laboratory and preserved in 10% formalin. The fishes were identified using the taxonomic key. The biodiversity status, abundance and distribution were described by the Shannon-Weiner diversity index, Margalef’s index, Sampson’s dominance and evenness index which were determined using PAST software (version 3.11). A total of 61 fish species belonging to 8 orders, 18 families were identified. Based on the updated list of IUCN Bangladesh, the conservation status of the fishes were 6 vulnerable, 11 endangered, 2 critically endangered, 23 least concern, 8 near threatened, 11 not threatened. Out of 25 threatened fish species 10 species were abundantly available where 15 were rarely available. Among the studied sites of the river, Bangibacha ghat site was found fish biodiversity rich area based on the Shannon-Weiner diversity, Margalef’s and evenness index (3.56, 7.62 and 0.62 respectively). On the other hand, Simpson’s dominance index was found highest (0.11) at the Karnai area and the lowest (0.04) at the Bangibacha Bridge area. The fishes of studied sites were found at the risk of extinction due to the habitat destruction and over exploitation. To protect the fish from the being extinction, establishment of another fish sanctuary at Bangibacha ghat sites are highly required.