Assessment of Pennahia macrocephalus stock in Beibu Gulf by length Bayesian biomass estimation method

Pennahia macrocephalus, one of the major commercial fishes in the Beibu Gulf, is of great significance to study its stocks status. Based on the biological data of P. macrocephalus collected in the Beibu Gulf from 2006 to 2014, we estimated the asymptotic body length (L_∞), relative natural mortality (M/k), relative fishing mortality (F/k), relative total mortality (Z/k), optimal body length-at-first-capture (L_{c_opt}), exploitation rate (E) and relative biomass index (B/B₀) by the length-based Bayesian biomass estimation method (LBB). Results show that the average L_∞ and L_{c_opt} were 265 mm and 157 mm, respectively, and the relative mortality rates of M/k, F/k and Z/k were 1.39, 3.58 and 4.96, respectively. The L_{c_opt} of P. macrocephalus showed an increasing trend while the L_∞ showed a decreasing trend. At present, the E of P. macrocephalus is relatively high (0.58), indicating the resources have been in the state of overexploited. The B/B₀ is less than 0.5, indicating the overexploitation of current stocks.