Mitochondrial Genetic Diversity and Demographic History of Critically Endangered Oreochromis karongae (Trewavas, 1941) Along Lake Nyasa, Tanzania

Fish provide food and income opportunities for millions of people in Lake Nyasa, also known as Lake Malawi in Malawi and Lake Niassa in Mozambique. Oreochromis karongae (Trewavas, 1941), which is native to Lake Nyasa, Lake Malombe and the Shire River, is at the verge of extinction and has been listed as critically endangered species by the International Union for Conservation of Nature (IUCN), primarily due to overfishing. Using 632 bp of partial mitochondrial cytochrome oxidase subunit I (COI) sequences from 115 samples, this work aims to assess the population genetic status and demographic history of this species to better manage and advance its conservation. The analysis of molecular variance (AMOVA) revealed a low and non-significant genetic differentiation index across the populations under study (ΦST = 0.003, p = 0.278), indicating a lack of population genetic structure. Phylogenetic analysis, grouped together all COI haplotypes of O. karongae from the six sampled sites. Nonetheless, the results showed signs of population expansion from a historic bottleneck, consistent with most data from the Western Indian Ocean Fauna. The findings from this study could be used to improve management and conservation strategies for critically endangered O. karongae in Lake Nyasa.