Amid declining fish diversity and human pressures in freshwater ecosystems, robust basin-scale assessments are vital for effective fisheries management. This study collated nearly four decades of fishery yields from the Pearl and Yangtze Rivers to identify conservation priorities in the Pearl River Basin. It introduced a novel cumulative effect indicator based on zeta diversity—a biodiversity pattern metric—integrated with cumulative effects analysis for management decision-making. The research employed a multi-site generalized dissimilarity model to examine the non-linear relationships between fish species composition (ζ_n) and human pressures, environmental factors, and geospatial variations across elevation gradients. The cumulative effect indicator, reflecting responses to anthropogenic stress when assessing ζ₂ (related to β diversity), helped evaluate basins for conservation or restoration needs based on their unique or homogenized biotic communities. The results suggest that ζ diversity in low-elevation sub-basins has a stronger filtering effect on ζ by human pressures than in mid- to high-elevation sub-basins, where community aggregation is more random. The impact varied with diversity aspects (nestedness vs. turnover) and zeta order. A negative correlation between cumulative effects and community uniqueness validated the novel cumulative effect indicator’s effectiveness for guiding restoration in the Pearl River Delta, potential fishing bans, and karst conservation. This approach offers a theoretical basis for prioritizing areas for freshwater fish diversity conservation and fishing restrictions in the Pearl River Basin.

The introduction of non-native fish species into southern China has been widespread, with tilapia being a major contributor. Commonly known as tilapia, Coptodon zillii, Oreochromis niloticus, and Sarotherodon galilaeus, have become the most common non-native fish in southern Chinese waters, even becoming the dominant species in some waters. In order to elucidate the seasonal and spatial distributions and environmental drivers of three tilapia species in the inland waters of Guangxi, systematic sampling was performed at 34 sampling sites in the major water systems through the four seasons in 2023. A total of 6093 specimens were collected, of which C. zillii dominated the catch (59.74%). In addition, the occurrence frequency of C. zillii was 92.65%, O. niloticus was 80.88%, and S. galilaeus was 45.59%. Seasonally, all species exhibited pronounced seasonality, peaking in summer and declining to winter minima. Similarly, principal coordinate analysis (PCoA) indicated summer dispersion to a greater extent, while winter dispersion was the least of the four seasons. Spatially, C. zillii dominated the northern study area, and there was no distribution of S. galilaeus, while the proportion of S. galilaeus and O. niloticus increased as latitude moved south. The Mantel test showed three tilapia species correlated with latitude, temperature seasonality, and the min temperature of the coldest month. In addition, the results of the Generalized Additive Model (GAM) showed that the number of three tilapia species was also affected by water environmental factors: S. galilaeus was affected by turbidity, O. niloticus was affected by pH and COD_MN, and C. zillii was affected by TN and water temperature. These findings highlight the synergistic effects of environmental gradients and spatial factors in shaping tilapia distribution, providing critical insights for freshwater ecosystem management under climate change.