The freshwater wild tilapiines are vital for augmenting aquaculture and economic development in Uganda. On the other hand, aquaculture development plays a pivotal role in the sustainability of wild fish stocks through minimizing overfishing threats. Therefore, both sectors play symbiotic roles in supporting each other. However, several challenges constrain aquaculture and wild/capture fisheries, including poor performance of the former. Most notably, the rampant, uncontrolled translocation of genetic materials, particularly tilapiines, between aquaculture systems and natural water bodies, could lead to a decline in biodiversity and ultimately threaten fish production and productivity. Currently, there is a paucity of information on the distribution and introduction of non-native strains and their potential effects on biodiversity in the Lake Victoria Basin. Additionally, albeit several factors that affect the aquaculture development, including water quality, fish feeds, and seed quality, are known, the genetic effects that could derail the performance of fish in captivity are less investigated. To address these gaps, we employed multi-genetic tools such as SSR, mtDNA, and SNPs to understand the genetic structure, diversity, and introgression levels of the key tilapiine species: O. niloticus, O. esculentus, O. variablis, and O. leucostictus. Our results revealed evidence of introgressive hybridization between the tilapiines. The results also indicated genetic admixture and structure based on the geographical location, with some populations revealing panmixia. We observed that pond-based Nile tilapia farms are admixed, contrary to cage fish culture. The genetic threats to the wild tilapia are mainly influenced by fish translocations. The genetic admixture in the pond-based Nile tilapia culture may contribute to the continued poor performance of the fish farms. These results are key to making informed decisions regarding the sustainable management of the wild fish stocks and aquaculture systems to enhance production and productivity in Uganda and in the EAC.
Keywords: Oreochromis niloticus, hybridisation, admixture, fish translocation, aquaculture