Original Contribution to the Theory of Fisheries-Independent Abundance Estimation using Acoustic Telemetry in Nigerian Inland Waters

Conventional fisheries-dependent abundance estimation methods for Nigerian inland fisheries are subject to substantial sampling biases arising from gear selectivity, non-random spatial effort distribution, and reporting inaccuracies, yet alternative fisheries-independent methods appropriate for the logistical constraints of Nigerian inland water bodies have not been theoretically developed or validated. This study makes an original theoretical and methodological contribution to fisheries-independent abundance estimation through the adaptation and validation of acoustic telemetry-based mark-resight models for two case study water bodies: Shiroro Reservoir in Niger State and Oguta Lake in Imo State. The original methodological contribution involves the derivation of a spatially stratified Bayesian mark-resight estimator that explicitly accounts for heterogeneous fish detection probabilities arising from variation in acoustic receiver coverage density and fish movement patterns. Acoustic transmitters were surgically implanted in 120 Lates niloticus in Shiroro and 80 Clarias gariepinus in Oguta Lake. Fixed and mobile receiver arrays were deployed to create detection grids. The spatially explicit Bayesian estimator produced population abundance estimates with credible interval widths 34% narrower than conventional Petersen mark-recapture estimates computed from the same data. Validation against electrofishing depletion estimates at accessible shoreline sections confirmed the accuracy of the acoustic telemetry-based approach. The study establishes the theoretical basis for standardised acoustic telemetry-based stock assessment in Nigerian inland fisheries and recommends a phased national implementation plan under the coordination of the National Institute for Freshwater Fisheries Research.

Keywords: acoustic telemetry, abundance estimation, Bayesian model, inland fisheries, Nigeria