Establishment of wild tilapia population community in main rivers of southern Guangxi.
[Objective]: The distribution and species of wild tilapia in the main rivers of southern Guangxi were investigated, and whether the tilapias have established stable population community was determined. It would provide effective basis for protecting the diversity of fish resources and preventing and controlling the ecological invasion of tilapia in the main waters of southern Guangxi. [Method]: Sampling points were set in main rivers in southern Guangxi. Tilapia samples were collected by netting and angling. Tilapia samples were taken back to the laboratory for anatomical measurement, and the total length, body length, body weight and other characteristics were counted. Gonads were taken for identification of males and females and gonadal development stages. The age composition was studied by observed scales. Correlation of body length-body weight and the fatness coefficient were also calculated. [Result]: The study found that wild tilapia populations existed in the main river systems in southern Guangxi, the main populations were Nile tilapia(Oreochromis niloticus) and redbelly tilapia(Coptodon zillii). It was found that the age of individuals was mainly one year old, but there were many individuals were two years old or above. The whole population was at young age. Gonads development of wild tilapia was fine. The sexually mature individuals accounted for high proportion of the total samples. Correlation of body length-body weight showed that the growth of Nile tilapia in Baise, Wuxuan and Wuzhou was allometric growth in the open air, while that in other sampling sites was uniform growth. The growth of redbelly tilapia in each sampling point was uniform in the open air. The results of fatness calculation showed that the average fatness of Nile tilapia and redbelly tilapia were 3.25-4.05 and 3.44-4.18, respectively. It showed that the wild tilapias grew well in the wild in southern Guangxi. [Conclusion]: Wild tilapia has successfully established populations in the main water system of southern Guangxi, and has a good living condition. The administration concerned should strengthen the supervision of wild tilapia in time to prevent it from further expanding and endangering native fish populations.