Small indigenous fish species (SIS) play a vital role in providing animal protein sources for human. The Gorai river, a Ganges tributary is a habitat of considerable number of SIS. A total of 11040 individual from 40 species were collected belonging 7 orders and 19 families using 5 fishing nets and 1 fish trap of which 2 species were critically endangered, 7 endangered, 7 species vulnerable, 18 species not threatened, 2 data deficient and 4 species were not in evaluated category. Dominant orders were Cypriniformes and Perciformes each contained 12 species, dominant family was Cyprinidae (11 species) and most dominant species was Chela cachius (2253 individuals). Diversity indices ranges from Simpson's dominance index (0.06-0.09), Simpson's index (0.91-0.94), Shannon Weiner index (3.08-3.24), Evenness (0.56-0.66), Menhinick's index (0.61-0.67), Margalef's index (4.48-4.77), Equitability (0.84-0.89) and Fisher alpha (5.86-6.31), respectively. Highest numbers (38) of SIS were caught by set bag net. Maximum total length 4.6 cm of Corica soborna was the new record. Considering the nutritional importance and reducing number of SIS inhabiting in the river Gorai, the present study aimed at documentation of SIS, their threatened status and conservation of SIS through laws and regulations.

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Sandha River water regime is used as a nursery, feeding and breeding places by commercially important fish species due to the presence of unique environment. Therefore, the present study has been conducted to assess water quality parameters, fish species abundance, fish diversity indices, conservation issues and management policy to guard the valuable aquatic resources of Sandha River from March 2015 to February 2016. Among the water quality parameters, temperature and pH were found at a slight rising level which possessed insignificant negative correlation with fish species abundance (p<0.01). Fish diversity indices were calculated of which the value of Shannon-Wiener Index just above 3 which indicated the river ecosystem still approving good fish community structure where lower value of richness described short food webs. Garretts Ranking Technique was applied to identify the reasons behind the decline of Sandha River fish species over the periods. The study, therefore, concluded that the river has experienced with slight climate modifications and significant anthropogenic activities especially huge fishing pressure which in a feedback reduce the fisheries stock resources with time. Community-based fisheries management (CBFM) hence would be an appropriate tool to make the water resources sustainable.

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