The Efficacy of Fisheries Management: A Length-Based Stock Assessment of Eight Fish Species in Xingkai Lake, China

Standardized fishing gear represents a common fisheries management intervention, yet its effectiveness in multi-species freshwater ecosystems remains insufficiently assessed. This study presents the first application of the Length-Based Bayesian Biomass (LBB) method to systematically evaluate the stock status of eight major commercial fish species in Xingkai Lake (located within China). Length-frequency data collected in 2019 (marking the policy initiation) and 2024 (after five years of implementation) were used to estimate key population parameters and exploitation indicators. The results revealed that the four species (<i>Carassius gibelio</i>, <i>Acheilognathus macropterus</i>, <i>Hemiculter lucidus</i>, and <i>Hemiculter leucisculus</i>) recovered to healthy status (<i>B/B_MSY</i> ≥ 1.0), demonstrating the policy's effectiveness for small-bodied, fast-growing species. In contrast, three species (<i>Chanodichthys abramoides</i>, <i>Chanodichthys mongolicus</i>, and <i>Chanodichthys erythropterus</i>) remained grossly overfished (<i>B/B_MSY</i> < 0.5), while <i>Culter alburnus</i> experienced increased fishing pressure, indicating limited efficacy for larger, slow-growing species with collapsed initial stocks. Although the mesh size increase facilitated recovery of specific populations, fisheries resources in Xingkai Lake continue to face overfishing pressure. Management strategies lacking an ecosystem perspective may not only fail to achieve conservation objectives but could also trigger ecological risks. This study underscores that ecosystem-based management is essential for sustainable management of multi-species fisheries.