Clupeids in the kaptai reservoir, a blessing or a curse: estimation of fisheries reference points

Abstract

Sustainable fisheries management depends on the degree of the present exploitation status of significant fish stocks. A recently developed fish stock assessment approach, CMSY, was used to estimate the fisheries reference points of data-limited Gudusia chapra and Corica soborna from the Kaptai reservoir using catch data, resilience, and exploitation records during the first and last year of the time series catch data. CMSY, along with a Bayesian state-space Schaefer production model (BSM), estimated maximum sustainable yield (MSY) as 2680 mt and 2810 mt, and 3280 mt and 3020 mt for the above stocks, respectively. The MSY range for both stocks was higher than the last catches meaning that both stocks are perfectly sustainable. The lower biomass B (4340 mt) for G. chapra estimated by CMSY and BMSY (4490 mt) indicates that the stock has started to be depleted. However, considering the precautionary fisheries management, the lower limit of MSY might be suggested to follow. Therefore, it could be suggested not to exceed the MSY limit (2680 mt) for the sustainability of G. chapra stock while it was 3020 mt for the C. soborna fishery. The intrinsic growth rate r was 0.862–1.19 yr−1 for G. chapra and 0.428–0.566 yr−1 for C. soborna, suggesting a high and medium increase of biomass in the existing population, respectively. A F/FMSY less than 1 and B/BMSY greater than 1 report both stocks at underfishing and underfished states. The study recommends enforcing strict and lawful actions regarding the net's mesh size to catch less small fish. Otherwise, negligence of this crucial management practice may bring severe threats to the sustainability of the whole reservoir resources and the reservoir ecosystem.