Fish Stock Status and Its Clues on Stocking: A Case Study of Acanthopagrus schlegelii from Zhanjiang Coastal Waters, China

Global fisheries face overfishing challenges, endangering fish stock and biodiversity. While hatchery release stocking programs aim to bolster fish populations, their effectiveness remains uncertain due to challenges in data acquisition, such as obtaining stocking details and differentiating between wild and stocked individuals. This study evaluates the stock status of black sea bream (Acanthopagrus schlegelii) released in Chinese hatchery programs since the 1980s. Samples from Zhanjiang fish markets (January 2019–October 2021) underwent analysis using the length–weight relationship (LWR), length-based spawning potential ratio (LBSPR), and length-based Bayesian (LBB) methods. The male and female LWRs were W = 0.0188L2.9725 and W = 0.016L3.0284, respectively, and the observed condition factors indicated good health. The estimates imply that the region is conducive to species survival and can sustain its stocking programs. The LBSPR (SPR = 0.21 (0.17–0.25)) and LBB (B/BMSY = 1.1 (0.718–1.34), B/B0 = 0.37 (0.253–0.473)) results suggest a rebuilding population capable of replenishing to more sustainable levels. However, F/M and net selectivity estimates indicate that fishing practices target juvenile fish, limiting the reproductive potential of A. schlegelii. These findings underline the need for enhanced management strategies, including delayed harvesting and the use of size-specific fishing gear, to ensure the long-term sustainability of the species.