The Bombay duck (Harpadon nehereus) forms the second-largest single-species marine fishery in Bangladesh and therefore has a significant impact on the local economy, providing employment, food, and nutrition to thousands of people. Despite the immense importance, this fishery has never been a priority for the relevant regulatory authorities. To enhance the sustainability of this fishery, an effective management policy based on the scientific evaluation of the current stock’s status is urgently required. Therefore, this study used three methodological approaches (traditional size structure-based stock assessment to reveal current exploitation status; the length-based spawning potential ratio (LB-SPR) to evaluate the stock’s spawning biomass; and Froese’s sustainability indicators for sustainable fishing) to conduct a thorough assessment of the Bombay duck stock to establish basic standards for the sustainable management of this fishery. The results revealed that this fishery is presently suffering from overexploitation and the stock’s spawning biomass (SPR = 8%) is below the limit reference point because of the juvenile-oriented fishing behavior of the fishery. Based on the outputs, this study recommended the mesh size regulation of the set bag nets (SBNs) (5 cm mesh size for the codend) to ensure not to catch immature fishes with a length equal to or smaller than 17.95 cm; and reduce the existing number of SBNs by half to reduce fishing pressure on the stock to ensure the sustainability of this fishery.

The two economically important shrimp species in Bangladesh are the tiger shrimp, Penaeus monodon, and the brown shrimp, Metapenaeus monoceros. However, a continuous decline in the landing of these species from the industrial trawling made it critical to assess their stock biomass status to explore their response to the present degree of removal. Given the minimum data requirement and robustness, this study employed the depletion-based stock reduction analysis (DB-SRA) to assess these fisheries rigorously. For the industrial fishing zone (beyond the 40 m depth in the EEZ of Bangladesh), the estimated historic mean carrying capacity (K) was 5015 metric tons for the Penaeus monodon and 35,871 metric tons for Metapenaeus monoceros. The estimated overfishing limits (OFL), which were much smaller than the reported catches throughout the time series, indicate the overfishing status of these fisheries. As a result, the estimated biomass for the reference year (B₂₀₂₀) for both species was lower than B_MSY, indicating that these fisheries are not producing MSY. Therefore, for the rebuilding and sustainable management of these stocks, this study recommended a catch limit of 100 metric tons for P. monodon and 750 metric tons for M. monoceros for the next ten years from biomass projections.

The present study was conducted to measure the heavy metals (Pb, Cd, Hg) concentrations in the muscles of four edible mollusk species (Perna viridis, Crassostrea crassostrea, Sepia officinalis and Loligo edulis) for two seasons. The heavy metal concentrations were analyzed by Atomic Absorption Spectrophotometer (AAS). The wet weight concentration of heavy metals varied for Pb: 0.03 - 0.05 1mg/kg, Cd 0.03 - 0.04 mg/kg and Hg 0.01 - 0.023 mg/kg. The trend of metals in mollusk muscles were found as Pb > Cd > Hg. There was no significant variation of Cd and Hg concentrations in mollusk species that were analyzed, but Pb varied (F = 22.297; p = 0.00), in terms of both seasons and species. Principal Component Analysis and correlation matrix showed significant anthropogenic intrusions of Pb, Cd and Hg in mollusks. There was significant positive correlation between Cd vs Pb (1.00) and Hg vs Cd (0.447) indicates their common origin especially from industries and municipal wastes. The determined concentrations of all metals in the present study were lower than the limits permitted by World Health Organization (WHO) and European Union (EU) guidelines. Bangladesh J. Zool. 44(1): 123-131, 2016