Species Portfolios for Climate-Smart Integrated Multi-Trophic Aquaculture in Coastal Kenya: Ecological Compatibility, Production Potential and Scaling Pathways

Integrated multi-trophic aquaculture (IMTA) is increasingly recognized as a climate-smart approach for improving aquaculture productivity, nutrient-use efficiency and environmental performance in coastal systems. However, successful IMTA development depends on selecting functionally compatible species portfolios. This PRISMA-guided review synthesized evidence on candidate species for IMTA integration along the Kenyan coast, with emphasis on ecological compatibility, production potential, environmental function, seed availability, health risks, market readiness and scaling pathways. Literature was searched in Scopus, Web of Science, ScienceDirect, Google Scholar, and FAO repositories using terms related to IMTA, mariculture, coastal aquaculture, seaweed, bivalves, sea cucumbers, gastropods, finfish, crustaceans and climate-smart aquaculture. Of 642 records identified, 527 remained after duplicate removal, 106 full texts were assessed for eligibility and 78 sources were retained for qualitative synthesis. The review identified marine tilapia, rabbitfish, milkfish and mullets as potential fed or partially fed finfish anchors for pond, pen and cage-based systems. Seaweeds, particularly Gracilaria, Ulva, Kappaphycus and Eucheuma, offer potential for dissolved nutrient uptake, while oysters provide particulate filtration but require strict food safety and depuration protocols. Sea cucumbers, polychaeta worms, sea urchins, and benthic gastropods such as Terebralia and Telescopium spp. are promising deposit-feeding components for reducing benthic organic loading. Mud crabs and shrimps offer economic diversification but require careful management because of predation, feed demand and biosecurity risks. The most feasible near-term portfolios include finfish–seaweed–sea cucumber, finfish–oyster–seaweed, finfish–gastropod–sea cucumber and finfish–seaweed–benthic invertebrate systems. Key constraints include weak hatchery capacity, unreliable seed supply, disease surveillance gaps, limited biosecurity, market uncertainty, lack of skills to manage a multispecies system, challenges on species compatibility and inadequate long-term ecological monitoring. The review proposes a species-selection framework linking trophic function, system design, environmental service, farmer capacity and value-chain readiness to support climate-smart IMTA scaling in coastal Kenya.