International Journal of Aquaculture, 2025, Vol.15, No.3, 135-148 http://www.aquapublisher.com/index.php/ija 144 7.3 Contradiction between genetic pollution and natural population protection Large-scale breeding of tilapia and multi-line introduction of species inevitably brings genetic pollution to wild relative populations and native fish. Genetic contamination refers to the hybridization of farmed fish with wild fish, or foreign lines with local lines, resulting in dilution or alteration of the genetic purity and genetic characteristics of the original population. On the one hand, in Africa, local tilapia species exist in some natural waters (such as Mozambique tilapia, Galaria tilapia, etc.). When people introduce Nile tilapia into these waters for breeding, hybridization may occur between different species, and the hybrid offspring produced breaks the original species boundaries, which may cause the unique gene pool of certain species to disappear in the long run (Ciezarek et al., 2024). On the other hand, in foreign countries, some of the original indigenous fish in the territory may also cross with escaped tilapia. For different tilapia strains introduced from abroad, hybridization during breeding may also reduce the purity and performance stability of the breeding strains (Figure 2). Faced with the risk of genetic pollution, there is a certain contradiction between fish resource protection and breeding production: an overly strict isolation policy may limit the development of the breeding industry, but if left unchecked, it may cause irreversible damage to biodiversity. Figure 2 (a) ADMIXTURE analysis of all O. shiranus-O. placidus, “Chambo”, and O. chungruruensis atK=2andK=3.(b)The proportion of species-diagnostic SNPs which are either homozygous for the alternate allele (Hom.), heterozygous (Het.), or homozygous for the reference allele (ref.) in the three O. chungruruensis individuals (abbreviation shi-plac-O. shiranus + O. placidus). *indicates genetically identified O. shiranus shiranus × “Chambo” hybrids in Lake Itamba (Adopted from Ciezarek et al., 2024) 8 Technical Innovation and Future Paths 8.1 The application potential of precision breeding and gene editing in tilapia Since the 21st century, cutting-edge advances in life sciences have brought revolutionary opportunities for tilapia breeding. Among them, genome selection and gene editing are highly expected to significantly improve breeding efficiency and break through target trait improvements that are difficult to achieve in traditional technologies. Genome selection (GS) uses genome-wide marker information for breeding value evaluation, has been successful in varieties such as Atlantic salmon and has also begun to be used in tilapia. A review pointed out that the growth genetic progress of tilapia in each generation through GS can reach more than 10%, which is far higher than that of traditional methods. Some leading institutions (such as WorldFish) have established SNP chips and breeding databases for tilapia to lay the foundation for precise breeding. In the future, as sequencing costs further reduce, large-scale genome-wide selection will be more feasible. Gene editing (GE) provides tools for directly modifying
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