Marine cage aquaculture suitability, Kenyan coast

Kenya's coastal waters hold considerable potential for marine cage aquaculture, yet site selection has historically relied on opportunistic assessment rather than rigorous environmental evaluation. This study presents an integrated biophysical suitability assessment of four coastal creek systems – Mida Creek, Kilifi Creek, Takaungu Creek, and Mtwapa Creek – spanning approximately 110 km of the Kenyan coastline. Bathymetric surveys, in-situ physicochemical measurements, nutrient sampling, plankton assessments, and acoustic current profiling were integrated within a multi-criteria evaluation framework benchmarked against FAO guidelines for marine cage aquaculture. Bathymetric surveys revealed pronounced morphological variability among sites. Kilifi Creek and Mtwapa Creek offered the greatest depth ranges (up to 43 m and 31 m respectively), with substantial proportions meeting minimum depth requirements for cage installation, while Takaungu Creek (mean 1.95 m) and Mida Creek (mean 3.32 m) were largely unsuitable on depth criteria alone. Water quality parameters were generally within acceptable ranges for marine finfish culture across Kilifi and Mtwapa creeks, with tidal dynamics strongly influencing nutrient distribution and phytoplankton community structure. Current measurements at Mtwapa Creek confirmed a regular twice-daily tidal cycle with mean mid-water column current speeds of approximately 0.20 m/s, which is within the optimal range for cage flushing and waste dispersal. Suitability scoring favoured mid-water column depths for cage deployment, with near-surface layers requiring careful engineering consideration due to elevated peak current speeds. These findings provide the first evidence-based site ranking for marine cage aquaculture along this coastline, with Kilifi and Mtwapa creeks identified as priority candidates for development, offering actionable guidance for spatial planning, investment and Blue Economy development.