Length-based indicators for the sustainability of small-scale fisheries in the Northern Bay of Bengal Coast, Bangladesh

Abstract

The small-scale fisheries in the northern Bay of Bengal coast of Bangladesh have been suffering due to an uncontrolled expansion of the fishing effort. Given this, it is important for all stakeholders to understand the current stocks’ status and their response to the present degree of removal. This study used two different methodological approaches to assess six commercially important fish species’ stock status from this coast with fisheries representative length–frequencydata: a length-based Bayesian biomass estimation method (LBB) for relative fishing mortality and stock biomass, and Froese’s length-based indicators (LBIs) for the sustainability of the fisheries. The present findings revealed that the biomass of Bregmaceros mcclellandi, Escualosa thoracata, Ilisha filigera, Johnius belangerii and Coilia dussumieri was below the target reference points (B/BMSY < 1 in LBB and SB < SBtarget in LBIs), suggesting overfished status of those fisheries. The biomass of Megalaspis cordyla, on the other hand, was above the threshold level (B/BMSY=1.1 in LBB &SB > 0.4SBtarget in LBIs). Depending on the outputs, this study recommended not to catch fish with lengths equal or smaller than the length at first sexual maturity to avoid growth overfishing, exclude the mega-spawners (length >Lopt+10% of Lopt) from the catch for preventing recruitment overfishing, and bring the fishing mortality back to the sustainable level (F=M) by reducing the existing number of boats to its half for fisheries long-term survivability.