Evaluation of Fish Stock Enhancement Programme in Kainji Lake Reservoir, Niger State

Fish stock enhancement through cage-based hatchery production and reservoir stocking is an increasingly adopted management tool to offset declining yields in overfished reservoirs. This study evaluated the effectiveness of the fish stock enhancement programme implemented in Kainji Lake Reservoir, Niger State, North Central Nigeria. The evaluation combined secondary data analysis of stocking records and landing statistics from 2020 to 2024 with post-stocking biological monitoring surveys conducted at six reservoir stations. Tagged juveniles of Oreochromis niloticus and Heterotis niloticus were stocked at three density levels, and recapture rates at fisher landing sites were monitored over a twelve-month period. Catch per unit effort trends before and after stocking were compared using time series analysis. Tag return data from 1,240 recaptured fish provided information on growth, survival, and dispersal patterns. Oreochromis niloticus showed higher recapture success (14.2%) compared to Heterotis niloticus (6.8%). Catch per unit effort improved significantly by 22 percent at stations within 15 kilometres of the stocking release points. However, fishers at distant stations reported no catch improvement, indicating limited dispersal of stocked individuals. Post-stocking genetic analysis confirmed no hybridisation between stocked and wild populations. Cost-benefit analysis of the stocking programme indicated a positive return of 1.8 naira per naira invested based on increased landing values. The study identifies stocking density optimisation and spatial distribution of release points as key areas for programme improvement. Keywords: stock enhancement, Kainji Lake, reservoir stocking, fisheries management, Niger State.