Microsatellite Marker Analysis of Genetic Structure in Nile Tilapia (Oreochromis niloticus) Populations in Kainji Lake, Niger State

The Nile tilapia (Oreochromis niloticus) is one of the most economically significant freshwater fish species in Nigeria, supporting the livelihoods of thousands of artisanal fishers around Kainji Lake in Niger State, North Central Nigeria. Understanding the genetic structure of tilapia populations is critical for sustainable fisheries management and informed stocking policies. This study analyzed the genetic structure of O. niloticus from three sampling zones in Kainji Lake using microsatellite markers. Fin clip and scale tissue were collected from 120 fish specimens. DNA extraction was performed by proteinase K digestion, and six polymorphic microsatellite loci were amplified by fluorescently labeled PCR primers. Fragment analysis was performed on a capillary electrophoresis platform. Allelic data were analyzed for Hardy-Weinberg equilibrium, FST, and effective population size using Arlequin 3.5 and GenAlEx 6.5. Moderate genetic differentiation (mean FST 0.08) was detected between sampling zones, suggesting partial population structuring. Bottleneck analysis indicated signs of recent effective population size reduction at two zones, likely linked to overfishing pressure. These findings provide baseline population genetic data to guide rational fisheries management at Kainji Lake. Keywords: Oreochromis niloticus, microsatellite markers, population genetics, Kainji Lake, Niger State.