Assessing the population genetic structure of yellow croaker in China: Insights into the ecological and genetic consequences of artificial breeding on natural populations

The large yellow croaker, a crucial marine economic fish in China, experienced a drastic decline in wild resource in the early 1980s due to overfishing and habitat degradation. Since the year 2000, the government has implemented habitat protection measures and initiated long-term, large-scale releases aimed at restoring this ecologically and economically important fish resource. Despite these efforts, there has been no definitive success in increasing the biomass of this overexploited species, and the underlying reasons for this lack of success remain elusive. Leveraging whole-genome resequencing data from a large number of samples encompassing both cultured and wild populations, this study offers the most exhaustive analysis of the genetic structure of large yellow croaker to date. The results revealed no significant geographical structure among the wild populations along the coast of China, overturning the long-held belief that designated them into three genetic management units. Additionally, it highlighted the absence of genetic introgression from cultured to wild populations. Furthermore, this study identified adaptive changes in cultured populations due to artificial selection and aquaculture environments, potentially reducing their adaptability to natural environments. This reduced adaptability may impact the survival rate of released populations and their hybridization with wild populations, providing insights into the limited success of previous release efforts. In light of these findings, this study recommends implementing conservation and management strategies based on a single genetic management unit for the large yellow croaker. When selecting breeding populations for hatchery releases, emphasis should be placed on genetic background considerations rather than solely relying on the origin of individuals captured in the sea. These insights hold significant implications for conservation and restoration of the large yellow croaker resource, particularly in the management of germplasm resources.