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 stock 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.

This study presents the results of analytical assessment of offshore shrimp stock in Bangladesh marine waters. A time series of annual catch per unit effort (CPUE) was derived from commercial logbook data during the period from 1986 to 2016 and used as a turning series for a Schaefer biomass model. The current stock size and annual harvest rate were estimated to be around 20300 t and 20% respectively, with the stock size increasing in the last ten years. The estimated maximum sustainable yield (MSY) reference points with 95% confidence intervals are optimal biomass B MSY = 15800 t (11300-22000 t) and optimal harvest rate u MSY = 30% (21-42%). The average annual catch was 4650 t, close to the estimated MSY of 4710 t (4570-4860 t). Overall, the stock is estimated to be in a good state and the data show that CPUE in recent years is slightly above the long-term average. The assessment results are subject to considerable uncertainty, reflected in wide confidence intervals around the estimated stock status. Moreover, the simple assessment model has restrictive assumptions that may not capture the underlying dynamics of the Bangladesh shrimp fishery, a multispecies tropical fishery with changes in the fleet composition and fishing technology. Nevertheless, the model fits well to the CPUE data and the assessment is a valuable basis for giving short-term and long-term management advice.

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 BMSY, 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.