Abstract
The physicochemical and biological attributes of a river ecosystem usually reveal the status of the subsistent aquatic life and affiliated species richness index of the biodiversity. The study was conducted to reassess the physical and biological condition of the 2nd Hilsa sanctuary of Bangladesh. Towards appraisal of water quality, physicochemical parameters (i.e., temperature, pH, DO, transparency and conductivity), and concentration of plankton were determined. Samples were collected from four different stations of 2nd Hilsa sanctuary areas with their special feature. The study revealed a slight spatial variation in physicochemical parameters of river water. While the parameters were found to be at acceptable levels, some measures are needed to improve the quality of water to ensure successful migration and reproduction of the Hilsa fish. The water quality parameter was found slightly alkaline (7.86 ± 0.31). The transparency was found (35.51 ± 25.32 cm) followed by water temperature (26.7 ± 3.86 °C), alkalinity (80.4 ± 15.27 mg/L), Hardness (134.33 ± 64.61 mg/L), CO₂ (11.46 ± 2.19 mg/L), DO (6.49 ± 0.79 mg/L), salinity (1.83 ± 1.48 ppt), biomass of phytoplankton, was estimated (30±5.1 ×10² cell/L) and zooplankton (8±2.9 ×10² cell/L). The largest quantity of plankton as a natural food (both in number and taxa) was found in the Meghna River basin compared to the other rivers. This assessment of the physical, hydrological, chemical and biological profile of the environment of the Hilsa fishery areas of the country delivers obvious evidence which is important to the apprising of the hilsa fisheries management action plan fo sustainable management in future.