International Journal of Aquaculture, 2025, Vol.15, No.1, 21-28 http://www.aquapublisher.com/index.php/ija 25 change in genotype frequency causes significant differences between the introduced population and the origin. This phenomenon of genetic drift has also been widely observed not only in Asia, but also in tilapia farming groups in the Americas. 5.2 Analysis of gene exchange between foreign populations and local populations The phenomenon of genetic exchange between foreign populations and native populations is equally common in tilapia farming. This communication is usually manifested as introducing populations to escape into the wild environment and then crossing with local wild populations. Florida, USA is a typical case. After a large number of breeding foreign tilapia escaped, they had extensive genetic communication with the local original fish population. The consequence of this communication is that the genetic structure of the native population has been significantly changed. Specific studies have shown that this hybridization will lead to reduced adaptability of native populations and even the disappearance of original unique genes (Angienda et al., 2011). Some studies also believe that this genetic communication may enhance the competitiveness of hybrid offspring in new environments to a certain extent. Therefore, how to reasonably control and manage these gene exchanges has become the common concern for aquaculture and ecological protection. 5.3 The challenge of genetic drift on the protection of tilapia germplasm resources Tilapia is native to Africa and the Middle East. Due to its fast growth rate, strong reproductive ability, low requirements for bait, strong adaptability and disease resistance, tilapia has been introduced to most parts of the world in recent decades, and its breeding output accounts for 11% of the global freshwater aquaculture production. Everything is a double-edged sword. A series of suitable characteristics such as fast growth and reproduction and strong environmental adaptability have also promoted its diffusion and invasion in natural waters, making it a “typical invasive species” (Figure 2). Currently, most tropical and subtropical areas around the world are threatened by tilapia invasion. In terms of resource volume, the tilapia resources account for 11.81% of the total catch in the main rivers in Guangdong, China. In some river sections, the tilapia resources even exceed the sum of other fish. It gradually reduces the genetic diversity of breeding populations, and even causes the disappearance of specific excellent genotypes; It also allows genes of foreign populations to be integrated into local wild populations, threatening the purity and characteristics of local populations (Tibihika et al., 2018). The spread and invasion of tilapia not only affects the stability of fishery resources and fishermen's income, but also poses a serious threat to biodiversity and the structure and function of aquatic biological systems (Mwanja et al., 2010). Figure 2 Tilapia in natural waters 6 Genetic Improvement Strategies for Tilapia Strains in Different Continents 6.1 Protection and utilization of native African strains Africa, as the origin of tilapia, has abundant wild germplasm resources. In order to protect the genetic diversity of tilapia, African countries have taken various measures. Establishing a germplasm resource library is one of them, ensuring that their genetic resources are not lost by collecting and preserving wild tilapia populations in different
RkJQdWJsaXNoZXIy MjQ4ODYzNA==