Evaluating Fishing Ban Effectiveness Through Spatiotemporal Changes in Genetic Diversity of Parabramis pekinensis

To scientifically evaluate spatiotemporal changes in genetic diversity of the bream (Parabramis pekinensis) population in the lower Yangtze River following the Yangtze fishing ban, temporal genetic diversity trends (2022-2024) were analyzed using mitochondrial Cytochrome b (Cytb) from three geographical groups (Anqing, Dangtu, Changshu), while genetic differentiation and gene flow patterns among seven geographical groups (Anqing, Tongling, Wuhu, Dangtu, Nanjing, Zhenjiang, Changshu) in 2024 were assessed through whole-genome resequencing. The analysis exhibited a fluctuating upward trend interannually in genetic diversity: Haplotype diversity (H _d ) increased from 0.918 to 0.957, total haplotypes rose from 43 to 50, shared haplotypes expanded from 8 to 12, and nucleotide diversity (P _i ) grew from 0.00283 to 0.00295. These metrics indicate that the overall genetic diversity of the population is maintained at a moderate level (0.5 < H _d < 1.0, 0.001 < P _i < 0.005); conversely, genetic differentiation exhibited a declining trend over time, with the fixation index (F _st ) decreasing from 0.00775 to zero, reflecting substantially enhanced genetic connectivity. Among the seven geographical groups sampled in 2024, minimal genetic differentiation was observed, with pairwise F _st values ranging between 0 and 0.0032. And Principal Component Analysis (PCA) revealed extensive cluster overlap without geographical segregation. These results indicate negligible population structure and unrestricted gene flow among bream populations in the lower Yangtze River. It provides critical molecular genetic evidence for the comprehensive evaluation of the fishing ban's effectiveness.