Asian Journal of Fisheries and Aquatic Research

This study assessed fish diversity, conservation status, fishermen's socio-economic conditions, and perceived causes of fish diversity decline in the Old Brahmaputra River (OBR) near Jamalpur District, Bangladesh, from January to December 2025. Monthly fish samples were collected from three sites, namely Nandina, Narundi, and Piyarpur, through professional fishermen. Socio-economic information and perceived threats to biodiversity were obtained through questionnaire interviews with 120 fishermen, supplemented by focus group discussions and cross-check interviews. A total of 3,245 fish specimens were examined, and 47 species belonging to 8 orders and 19 families were identified. Cypriniformes was the dominant order, representing 31.91% of the recorded species, followed by Siluriformes (27.65%) and Perciformes (19.14%). Based on local conservation status, 59% of the species were categorised as least concern, 15% as vulnerable, 13% as endangered, 11% as near threatened, and 2% as critically endangered. At the global level, 81% were least concern, 9% near threatened, 6% not evaluated, 2% data deficient, and 2% vulnerable. Species availability indicated that 40% of the fish were common, 28% less common, 17% abundant, and 15% rare. The socio-economic assessment showed that 70.83% of respondents depended mainly on fishing, 38.33% were aged 31-40 years, and 80.83% were married. Illiteracy was high (50%), while 14.70% had primary education and 5.88% had secondary education. About 58.82% lived in kacha houses, 67.64% had no savings, and 50% earned up to BDT 10,000 per month. Overfishing (88.23%), banned fishing gears (79.41%), harvesting of brood and juvenile fishes (76.47%), and habitat degradation (70.58%) were the major perceived threats. The findings indicate the need for conservation-oriented management and socio-economic support for fishing communities in the OBR.