Bioeconomic modeling of guitarfish and plaice populations under exploitation pressure in Moroccan coastal waters

This study develops a bioeconomic model to examine the interaction between ecological competition and harvesting decisions in Moroccan coastal fisheries. The analysis focuses on the Guitarfish ( Raja undulata ) and European Plaice ( Platichthys flesus ), two species sharing similar habitats and food resources. Ecological dynamics are described using coupled logistic growth equations with asymmetric interspecific competition, while system stability is investigated through equilibrium and local stability analyses. To incorporate economic considerations, harvesting strategies are optimized using Karush–Kuhn–Tucker (KKT) conditions under sustainability constraints. Numerical simulations reveal significant trade-offs between short-term profitability and long-term resource conservation. Intensive simultaneous harvesting increases immediate economic returns but may lead to rapid declines in Plaice biomass without strict regulatory measures. Conversely, more conservative harvesting strategies promote long-term stock persistence and ecological stability. Sensitivity analysis highlights the critical influence of competition coefficients on population dynamics, showing that small parameter variations can substantially affect species coexistence and stability. The proposed framework provides practical guidance for fisheries management through optimized harvesting policies and effort regulation. Although motivated by Moroccan coastal fisheries, the model is adaptable to other competing fisheries systems and supports broader objectives of sustainable marine resource management.