Assessing genetic variation in Nile tilapia populations across Sub-Saharan Africa: a review for conservation and sustainable aquaculture

Abstract

Nile tilapia (Oreochromis niloticus) plays a critical role in the nutrition and economy of tropical and subtropical regions, particularly in Sub-Saharan Africa. The rapid expansion of aquaculture and environmental pressures, such as the introduction of non-native strains, threaten the genetic diversity of this species. Understanding the genetic diversity of Nile tilapia populations is crucial for ensuring sustainable aquaculture and conservation efforts in the region. This review analyzes the genetic diversity of Oreochromis niloticus in Sub-Saharan Africa using various molecular markers. It examines genetic differentiation, heterozygosity, and population structure in farmed and wild populations, focusing on aquaculture, environmental pressures, and human activities. A systematic review of 105 studies provides insights for conservation and sustainable aquaculture development. The study highlights that wild populations maintain higher genetic diversity compared to farmed ones, which face genetic erosion due to limited gene pools and poor breeding practices. Inbreeding and hybridization pose further threats, particularly where non-native strains have been introduced for aquaculture. The review emphasizes the value of molecular tools like microsatellites, mtDNA, RFLP, and SNP for assessing genetic diversity and population structure. Despite challenges in using mtDNA for hybridization studies, SNPs provide more detailed insights. The review recommends adopting full-genome resequencing for improved genetic monitoring and management and advocates for conservation strategies, including protecting natural habitats and establishing fish and sperm banks, to preserve genetic diversity in regions like Lake Kivu and East Africa.