Environmental factors regulating temporal pattern of fish community and declining threats in the Khaliajuri haor wetland of Bangladesh.

Khaliajury haor (bowl or saucer shaped shallow depression) is one of the environmentally challenged wetland ecosystems in Northeast Bangladesh due to climate change and anthropogenic factors. The current research work is designed to study the abundance and diversity indices and the threats responsible for declining fish abundance from the haor region. Monthly sampling of water quality parameters and fish species was performed from July 2020 to June 2021. Fishermen's perception was assessed to determine the declining factors of fish abundance from the haor. A total of 59 fish and 3 prawn species were recorded belonging to 9 orders and 20 families. Cypriniformes was the most abundant group, accounting for 26.34% of the overall catch. Fish catch showed monthly variation with January (24.88%) and May (1.56%) recording the highest and lowest catch, respectively. Among the fish species, Puntius sophore (8.36%) was the most abundant species while the least contribution was noted for Bagarius bagarius (0.07%). Planktivore (32.09%) also showed the highest dominance among the trophic groups. Redundancy analysis (RDA) revealed DO as the most influencing parameter for 10 dominant species (Relative abundance > 2.5%). Furthermore, correlation analysis signifies the importance of water temperature, DO, pH, TDS, alkalinity, nitrate, and phosphate in structuring the total abundance of fish species in the Khaliajury haor. The present study identified the dewatering during dry months, overexploitation, destructive fishing practices, structures impeding fish migration, and siltation as the key factors for declining fish abundance in the Khaliajury haor. Enhancing and sustaining fish abundance and diversity in Khaliajury haor are suggested to significantly help through an ecosystem-based management strategy via sanctuary development and proper execution of acts and regulations.