Estimating Biological Reference Points of the Pink Shrimp, Farfantepenaeus notialis (Perez-Farfante, 1967) Targeted by Shrimp Trawlers in Sierra Leone

Abstract

Time series of catch and effort data for Farfantepenaeus notialis were analysed in ‘R’ using a data limited state-space Bayesian Catch-maximum Sustainbale Yield (CMSY) method for stock assessment from catch (tonnes) and abundance data (t/day). The study categorically compared the status of F. notialis in two periods (1981-1996) and (2008-2018) denoted as periods I and II, respectively. Results for management based on Bayesian Schaefer model (BSM) analysis for Period I gave (Prior relative biomass (B/k) = 0.06; MSY = 2.25t , 95% CL = 1.98 - 2.56; Fmsy = 0.379 yr-1 , 95% CL = 0.29 - 0.495; Bmsy = 5.94t , 95% CL = 4.69 - 7.51; Biomass = 4.78t; B/Bmsy = 0.806; Fishing mortality = 0.583yr-1 and Exploitation rate, F/Fmsy = 1.54) while that of Period II showed (Prior relative biomass (B/k) = 0.35; MSY = 0.662t, 95% CL = 0.567 - 0.773; Fmsy = 0.421yr-1 , 95% CL = 0.314 - 0.563; Bmsy = 1.58t , 95% CL = 1.22 - 2.04; Biomass = 1.09t; B/Bmsy = 0.69; Fishing mortality = 0.532yr-1 and Exploitation rate, F/Fmsy = 1.27). By implications, all estimated biological reference points portrayed an overfished status of F. notialis in 1989-1996 and in 2008-2018. Stock recovery measures are strongly advised for the stock in Sierra Leone.

Keywords

• bayesian
• exploitation
• fishing pressure
• reference point
• stock
• sustainability