Genetic Diversity and Spawning Patterns of Small Yellow Croaker (Larimichthys polyactis) in a Large-Scale Pooling System

Although mass-spawning pooling systems are widely used for small yellow croaker (Larimichthys polyactis) aquaculture, they often induce severe genetic bottlenecks driven by reproductive skew. This study evaluated cross-generational genetic diversity and spawning patterns to propose an optimal genetic management strategy. We analyzed 1049 adult broodstock and 950 juvenile offspring using nine microsatellite markers. To mitigate reproductive skew, fertilized eggs were collected via multi-time sampling (19 times) over a two-month spawning season and reared to the juvenile stage. Genetic diversity was highly conserved across generations, with expected heterozygosity maintained at 0.860 in the offspring. Parentage assignment succeeded for 96.2% of the offspring (914 individuals), revealing 802 unique families, of which 89.9% (721 families) were singletons. Also, 60.9% of the broodstock contributed to reproduction, exhibiting a right-skewed participation distribution. Importantly, comparisons with a short-term single-event collection control group demonstrated that our multi-time strategy effectively prevented drastic reductions in effective population size (Ne). These patterns highlight the species asynchronous spawning physiology and confirm that the strategy approximates random mating with minimal genetic drift. We suggest this long-term, multi-time egg collection method as an effective protocol for the sustainable genetic management of multiple-spawning marine fish.