Distribution and Driving Environmental Factors of Three Tilapia Species in the Inland Waters of Guangxi, China

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 CODMN, 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.