Impacts of Invasive Fish Species on Native Fish Species: Mechanisms, Evidence, and Management

Abstract Invasive fish species (IFS) are major drivers of biodiversity loss and ecosystem change in inland and coastal waters worldwide. Through predation, competition, habitat modification, hybridization, disease transmission, and indirect food-web effects, invasives reduce native species abundance and richness, erode genetic integrity, and alter ecosystem functioning. This review synthesizes recent evidence on impact pathways, highlights representative case studies (e.g., Nile perch in Lake Victoria; tilapias, Clarias spp., and Pterygoplichthys spp. in Asia), evaluates monitoring tools (notably environmental DNA), and outlines management and research priorities. Emphasis is given to quantitative attribution of impacts, the role of propagule pressure and environmental change, and integrated prevention–detection–response strategies.