Population structure and distribution characteristics of common wild tilapia in inland waters of Guangxi

【Objective】To accurately study the population structure and distribution characteristics of common wild ti‐ lapia in inland waters of Guangxi，which could provide important reference for the protection of biodiversity in Guangxi waters.【Method】From February 2023 to January 2024，3 common wild tilapia species were collected from 29 sampling points in inland waters of Guangxi，and taken back to the laboratory to measure their biological indicators such as full length，body length and body mass. The gonad was dissected out to identify the male and female and determine the go‐ nadal development stage，and their ages were determined according to the scales. The distribution characteristics and population structure of the 3 tilapia species，including body length and body mass distribution，age structure and sex ra‐ tio，were analyzed by Excel 2020，Origin 8.0 and ArcGIS 10.8.【Result】A total of 2648 tilapia were collected. There were 745 Oreochromis niloticus，1379 Coptodon zillii and 524 Sarotherodon galilaeus. The size of C. zillii was smaller than those of O. niloticus and S. galilaeus，and the 3 tilapia were basically in a state of uniform growth，with fullness > 1.00， and the tilapia in each sampling site grew well. O. niloticus and C. zillii were in the younger age group in Guangxi inland waters. The age distribution of S. galilaeus had certain regular characteristics，with older individuals mainly occurring in the lower reaches of Hongshui River and Xijiang River，while younger individuals were mainly distributed in Zuojiang River，Youjiang River and rivers that flowed into the sea. In general，there were more females than males in the 3 com‐ mon tilapia species in inland waters of Guangxi，with more males than females in some water systems. O. niloticus mainly distributed in the southern part of Guangxi，and less in the northern part of Guangxi. C. zillii could be found everywhere in the inland waters of Guangxi. S. galilaeus mainly distributed in Hongshui River and the main stream of Xijiang River， and there were also S. galilaeus distributed in Nanliu River.【Conclusion】O. niloticus and C. zillii tilapia have invaded the whole waters of Guangxi，and S. galilaeus is also distributed in most water systems in Guangxi，and its domestication de‐ gree can naturally overwinter in the northern part of Guangxi，affecting the biodiversity of local water ecosystems severels. Therefore，in the future，the impacts of tilapia and other alien fish invasions on aquatic ecosystems should be at‐ tached great importance to，systematic research on monitoring and control should be strengthened，and effective measures to prevent tilapia from moving northward should be taken.