Stock exploitation status of silver croaker (Pennahia argentata) from the East China Sea

Abstract

Silver croaker (Pennahia argentata) is an important economic species in the East China Sea (ECS); however, its population has been declining, and studies on its status are scarce. This study collected biological data, including length, weight, and gonadal maturity of silver croaker from the southern coastal waters of Zhejiang Province between 2015 and 2021, to evaluate its life history and assess stock status. Methods from the TropFishR package were employed to estimate population growth and natural mortality parameters. Two widely used length-based data-limited models, length-based bayesian biomass estimation method (LBB) and length-based spawning potential ratio method (LBSPR), were applied to assess the stock status of silver croaker in the ECS. The results indicated that with a maximum age (A_max) of 4 years, the asymptotic length (L_inf) was 23.80 cm, growth rate (K) was 0.74/year, and natural mortality coefficient (M) ranged from 1.068 to 1.376. Under the assumption of A_max = 5 years, L_inf was 26.77 cm, K was 0.63/year, and M ranged from 0.818 to 1.193. The LBB and LBSPR models showed that, except for scenarios with L_∞ = 23.8 cm, M/K = 1.46, and L_∞ = 26.77 cm, M/K = 1.30, 1.38, or 1.48, the selectivity at length parameters $L_{50}^S$and$L_{95}^S$ for silver croaker exhibited an increasing trend over the years. In the LBB model, $L_{50}^S$ for different years consistently fell below the optimum length (L_{c_opt}), indicating that most individuals did not reach the size at first sexual maturity or optimal catch length. Moreover, under high fishing pressure, the Spawning Potential Ratio (SPR) and the unfished biomass ratio (B/B₀) for silver croaker showed a decreasing trend, despite some stability or recovery in recent years. However, in all scenarios, SPR values were below 0.2, and B/B₀ values were below 0.5, suggesting a significant risk of population collapse for silver croaker in the ECS due to intense fishing pressure. Therefore, it is recommended to reduce the current fishing pressure and increase the minimum catch size of this species for effective conservation and management in this region.