Assessing Low Value Crustacean Bycatch Species Using Length Based Bayesian Biomass (LBB) Method, a Tool for Data Poor Fish Stock Assessment

The majority of tropical fish stocks lack sufficient data for conventional fish stock assessment, making them data-poor fisheries. The status of stock assessment is even more dismal for the low value fishes or crustaceans landed by the trawlers in a significant quantity. Crustaceans like non-edible small crabs (Charybdis spp) and stomatopods form a significant component of the low-value bycatch landed along the northwest coast. Despite the high ecological importance of these groups and the recent declining trend in catches (2007-19), no attempts so far have been made to evaluate the stock status of these groups from the study region. As reliable time series catch and effort data for the individual species are not available, a recently developed length-based approach, LBB (Length Based Bayesian Biomass) estimation method is adopted for the present study. Two of the evaluated stocks, Charybdis hoplites and Miyakella nepa were found abundant (B/BMSY>1.1), whereas Oratosquillina interrupta (B/BMSY=0.94) was found slightly overfished. The sufficient number of larger individuals were found lacking in all three species (L95th/L infinity<<1.0). A higher incidence of juveniles in catches was estimated for C. hoplites and O. interrupta (Lmean/Lopt<<1.0).