Socio‐Economic and Ecological Drivers of the Spread of Non‐Native Tilapia ( Oreochromis niloticus ) Species in Kenya

ABSTRACT Nile tilapia (Oreochromis niloticus) is the dominant non‐native fish species in Kenya's inland waters, but its spread reflects a coupled socioecological process rather than a simple biological invasion. This review examines the socio‐economic, governance and ecological drivers of its expansion within a socioecological systems and invasion biology framework, with evidence published between 2000 and 2025. A systematic search was conducted in Scopus, Web of Science, ScienceDirect, AGRIS, CAB Abstracts and Google Scholar, supplemented by institutional repositories and selected grey‐literature sources. The search identified 1220 records, of which 62 studies met the predefined inclusion criteria after screening and full‐text assessment in accordance with PRISMA guidelines. The 62 included studies indicate that Nile tilapia contribute substantially to fish production and rural livelihoods in Kenya. Strong market demand, food‐security objectives and production‐oriented policies have supported aquaculture expansion, stocking and movement of Nile tilapia between water bodies. These activities have increased opportunities for both intentional and unintentional dispersal, particularly through stocking programmes, hatchery distribution, aquaculture escapes and informal fish movements. The ecological evidence documents genetic introgression with native tilapiines, declines in native fish populations and changes in the fish community and trophic structure in several freshwater systems. However, the reviewed evidence indicates that the magnitude of these effects varies among systems and that native fish declines cannot be attributed to Nile tilapia alone because other anthropogenic pressures also contribute. The findings indicate that Nile tilapia spread is shaped by interactions among socio‐economic incentives and human‐ and non‐human‐mediated dispersal and governance conditions. Its economic and food‐security benefits can simultaneously create ecological risks where fish movement, hatchery practices and biosecurity are inadequately controlled. Fisheries management should therefore combine stronger hatchery traceability and biosecurity, regulation and monitoring of live‐fish movements, genetic surveillance and biodiversity safeguards with continued attention to food‐security and livelihood objectives.