BIODIVERSITY AND THREATENED STATUS OF FISHES IN THE DHEPA RIVER OF DINAJPUR, BANGLADESH

Abstract

The present study was conducted to assess the fish biodiversity and threatened status of fishes in the Dhepa River from September 2015 to April 2016. The fishes were collected from 3 sampling sites: Kantonagor area, Karnai area and Bangibacha bridge area of the Dhepa river in each month. Then the collected fish samples were identified by morphometrically and meristically and preserved with 10% formalin in laboratory. The Shannon-Weiner diversity index, Margalef’s index, Sampson’s dominance index and evenness were determined by using PAST software (version 3.11) to describe the abundance and distribution pattern of fishes. A total of 61 fish species belonging to 8 orders, 18 families and 11 major groups including prawns were identified. Cypriniformes was recorded as the most diversified fish group in terms of both number of species and number of individuals observed. The ShannonWeiner diversity index was found highest (3.56) at the Bangibacha bridge area and the lowest (2.84) at the Karnai area. Higher Shannon-Weiner diversity index value was found in September and November (3.41) where low during March (2.30). Margalef’s index was found highest (7.62) at the Bangibacha Bridge area during September (8.38) and the lowest (5.79) at the Karnai area during April (6.54). On the other hand, evenness index was lowest (0.37) at the Karnai area during March (0.19) and the highest (0.62) at the Bangibacha Bridge were in two successive months i.e., in January, February (0.61). The fish species of the Dhepa river found to be evenly distributed. Simpson's dominance index were found to be highest (0.11) at the Karnai area during March (0.23) and the lowest (0.04) at the Bangibacha Bridge area in five successive months i.e., in September, October, November, January and February (0.05) Species richness and evenness were increased in winter months and decreased in summer months on the basis of biodiversity index. Among 61 species 6 were vulnerable, 11 endangered, 2 critically endangered, 23 were least concern, 8 were near threatened 11 not threatened according to IUCN Bangladesh (2016). Among 25 threatened fish species, 10 species were abundantly available and 15 species were rarely available in the Dhepa River. Finally, it is recommended that establishment of fish sanctuaries could be the effective means to conserve both threatened and non-threatened fish species of the river.