Gorai River is one of the important rivers in Bangladesh for rich aquatic biodiversity. The river is originated from the Ganges-Padma River system, a trans-boundary river between India and Bangladesh. Once the river was rich in fish biodiversity, but due to man-made and natural causes the availability of fish reduced drastically. A comprehensive analysis of fish diversity indices, gear efficiency, catch composition and decline causes of fish diversity in Gorai River, Bangladesh was accomplished. The data were collected on monthly basis from January to December 2018 from three major fishing sites of the river. A total of 62 fish and 2 prawn species under 12 orders and 24 families were recorded. Cypriniformes was the leading order consisting 27% of the total catch. The mean values of Shannon-Weaver diversity (H 0 ), Simpson's index (1-D), Margalef's richness (d) and Pielou's evenness (J 0 ) indices were recorded as, 1.478 AE 0.495, 0.57 AE 0.197, 15.115 AE 4.435 and 0.481 AE 0.152, respectively. At the similarity of 58.7%, two groups were attained in the cluster analysis and the Non-metric Multidimensional Scaling (nMDS) showed 40% similarity among the three sites in twelve months based on the Bray-Curtis similarity matrix. The highest and lowest CPUE were recorded from seine net (5.2 AE 1.72 kg gear À1 haul À1 ) and hook & long lines (0.0135 AE 0.0015 kg gear À1 haul À1 ), respectively whereas, highest and lowest gear efficiency were recorded from lift net (0.321 AE 0.036 kg gear À1 person À1 hour À1 ) and fish trap (0.0005 AE 0.0002 kg gear À1 person À1 hour À1 ), respectively. Alternatively, the highest fish catch was recorded on April (21228 AE 464.38 kg) and lowest on August (3855 AE 138.21 kg). According to the fishermen fish biodiversity of the Gorai River declined day by day due to overexploitation, destructive fishing practice, pollution, construction of obstacles for fish movement, and natural causes like siltation. Proper implementation of fish acts and regulations, use of authorized fishing gear, community-based fisheries management, sanctuary establishment and management, stocking of fish fingerling, and raising public awareness can play a great role in enhancing and conserving fish biodiversity in the Gorai River of Bangladesh.

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Integrated aquaculture is an efficient method to address food scarcity and land resources. This study analysed the impacts of integrated rice–prawn–vegetable farms (RPVF) compared with conventional rice farms (CRF) on farming households in southwest Bangladesh, in terms of cropping pattern, financial profitability and viability, and cash-flow. Data were collected through face-to-face recall interviews from farmers of CRF and RPVF. For RPVF, farmers cultivated diverse produce in the wet season, such as prawn/shrimp, carps in reservoirs and vegetables on dikes, and boro rice with vegetables in the dry season, whereas only rice was cultivated in both seasons for CRF. The annual hectare−1 net revenue from integrated RPVF was USD 2742.7, 3.6 times higher than for CRF (USD 756.6). RPVF had a higher undiscounted benefit–cost ratio (BCR) of 1.58 as compared with 1.34 for CRF. Net Present Value (NPV) and discounted BCR show that the integrated RPVF has higher potential and profitability than CRF. Year-round vegetable production and selling have resulted in a smooth cash-flow in integrated RPVF. Authorised extension agencies, such as the Department of Fisheries and Department of Agricultural Extension collaboratively can promote RPVF in other potential parts of Bangladesh, through which farmers can benefit year after year by investing farm income for the same farm and envisage food security.

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