Spatial distribution, clustering and locational correlates of aquaculture enterprises in Nyeri County, Kenya

Abstract Spatially explicit information is necessary for aquaculture support, management and environmental planning. This study described the distribution of aquaculture farmers and production units, assessed spatial patterns, and examined locational correlates of aquaculture enterprises across the eight sub-counties of Nyeri County, Kenya. We analysed 1,203 registered farmer records, including 1,176 valid georeferenced locations for nearest-neighbour analysis and 1,191 farms for water-proximity analysis. Distribution was assessed using farmer counts, pond counts and pond area; spatial concentration was evaluated using kernel density and nearest-neighbour analysis; and farm locations were overlaid with agro-ecological zones, rivers, dams and roads. Registered farmers were relatively evenly distributed among sub-counties (Gini = 0.047), whereas pond counts (Gini = 0.110) and pond area (Gini = 0.301) were more unequal. Kieni East and Mathira East each had the largest number of registered farmers (167), Kieni East had the most ponds (250), and Mathira West had the largest pond area (73,520 m²). Farmer count was positively but not significantly correlated with pond count (r = 0.668, p = 0.070) and was not significantly correlated with pond area (r = -0.472, p = 0.238). Farm locations were strongly clustered: the observed mean nearest-neighbour distance was 0.354 km compared with an expected distance of 0.842 km, giving an index of 0.420 (z = -38.058, p < 0.001). Overall, 846 farms (71.03%) were within 1 km of a mapped river or dam. Relative to Kieni East, high-density cluster membership was more likely in Kieni West, Mathira West and Tetu, increased with pond count, and decreased with log-transformed pond area. The findings show that farmer participation, farm concentration and production-unit capacity have distinct geographies. An updated georeferenced registry would support differentiated extension, water management, pond rehabilitation, biosecurity, input delivery and market aggregation.