The current population genetic status of Oreochromis niloticus (Linnaeus, 1758) along the Malagarasi River, Tanzania

In East African countries, the O. niloticus species is the second most important fish species in terms of economic significance. However, localized overfishing, habitat degradation, and hybridization have resulted in populations’ decline that poses a threat to this species in this area. This study assessed the genetic diversity, population structure, demographic history, and effective population size of this species along the Malagarasi River. Comparisons were made between the population genetic structure and demographic history of populations of this species from Malagarasi River and other sites in the East Africa (EA) region. The study used COI gene sequences isolated from O. niloticus species collected along the Malagarasi River and COI gene sequences of this species from other sites in the EA region. The populations of O. niloticus from the Moyowosi had the highest haplotype diversity (0.80 ± 0.06) and nucleotide diversity (0.72 ± 0.41 %). At Ilagala, the lowest haplotype diversity (0.44 ± 0.13) and nucleotide diversity (0.16 ± 0.13 %) were found. Fixation index (Fst value) analysis resulted into significant genetic difference among the populations along Malagarasi River (Fst = 0.08419, P < 0.01). The Fst values and minimum spanning haplotype network revealed genetic break between population of O. niloticus from the Malagarasi River and other sites of the EA region. In order to ensure the sustainable exploitation of O. niloticus and other threatened fish species along the Malagarasi River, these findings urge for strengthening the implementation of fisheries laws, particularly in areas where samples exhibit low genetic diversity.