Genotype-by-Environment Interaction in Red Tilapia (Oreochromis spp.): Implications for Genetic Parameters and Trait Performance

The intensive farming of aquaculture species such as red tilapia (<i>Oreochromis</i> spp.) across diverse production systems can lead to changes in genetic parameters and responses of economically important traits in this species. This study represents the first attempt to understand these changes in growth traits (body weight, total length), quality attributes (body colour), and survival rate in red tilapia. Data for these traits were collected from 75,950 individual fish, progeny of 970 full-sib families (comprising 970 dams and 486 sires); they were selected for high body weight and evaluated in two distinct culture environments: fresh- and saltwater ponds. A multi-trait mixed model was employed to estimate genetic parameters and selection responses. Genetic variance estimates for the quality and survival traits varied across the two environments. However, genetic correlations among the traits studied were similar between fresh and saline water. Furthermore, significant G × E interactions, particularly for the quality and survival traits, were evidenced by divergent genetic correlations (<i>r_g</i> = 0.57-0.83) between homologous traits across different environments. The findings emphasise the importance of incorporating G × E interactions into the selection program for red tilapia, particularly when the breeding objectives extend to include quality and survival traits. Selection strategies should consider the prevailing culture system-for instance, favouring genotypes suited to the freshwater pond environment over those adapted to the saltwater environment. Continual assessment of full-sib groups across these environments is recommended to refine our understanding of G × E interactions and optimise future breeding programs for red tilapia. This may involve selecting genotypes capable of consistent performance across environments or developing environment-specific breeding programs.