Development of a Multi-Species Stock Assessment Framework for the Artisanal Fisheries of Lake Chad: Theoretical Foundations and Nigerian Application

The multi-species nature of the Lake Chad artisanal fishery, where interacting predator-prey relationships among target species complicate single-species management recommendations, requires a theoretically coherent multi-species assessment framework that has not been developed for this internationally shared water body from the Nigerian perspective. This study develops an original multi-species stock assessment framework for the Lake Chad artisanal fishery in the Borno and Yobe State sectors, grounded in predator-prey interaction theory and integrated ecosystem modelling. The framework combines species interaction coefficients estimated from diet composition studies with multi-species virtual population analysis to produce biomass trajectories and fishing mortality estimates for eight co-occurring target species simultaneously. An original feature of the framework is the explicit representation of nutritional linkages between the fishery and the food security status of fishing communities, creating a coupled socio-ecological assessment tool. Six years of species-specific catch and effort data from the National Agricultural Extension and Research Liaison Services landing monitoring programme were used to parameterise the model. Outputs include species-specific reference points accounting for inter-species competition, synergistic exploitation effects, and ecosystem productivity constraints. The multi-species maximum sustainable yield was estimated at 94% of the sum of single-species maximum sustainable yield estimates, indicating moderate species interaction effects. The study provides the most comprehensive quantitative stock assessment of the Nigerian Lake Chad fishery to date and recommends mandatory adoption of multi-species reference points in the Lake Chad Basin Commission's next joint fisheries management plan.

Keywords: multi-species assessment, Lake Chad, stock assessment framework, ecosystem modelling, Borno State