Fishing ground expansion and its consequences for estimates of sustainability in artisanal coral reef fisheries

Sustainable fisheries require balancing ecological production with resource capture, but this balance is often obscured by changes in the fishing area. Further, expansion of fishing grounds is commonly proposed to mitigate overfishing by dispersing effort and promoting nearshore recovery, but its long-term consequences remain poorly understood. We evaluated artisanal coral reef fisheries along Kenya's fringing reef over a 23-year period, comparing ecological and fisheries production in non-expanded and expanded fishing grounds. Seventy percent of landing sites expanded by an average of 5% annually. Fishery catches were assessed against ecological production using fish censuses (1987–2024) and a biomass-production model ( R 2 = 0.78). Area changes significantly influenced per-area effort and catch estimates, requiring interpolation between initial and final measurements. Across all methods, capture consistently exceeded ecological production estimates, indicating unsustainable capture rates. Both area categories exhibited an effort–catch resource capture overshoot dynamic, with expanded areas showing delayed but more pronounced declines in per-area effort and yield after peak catches. Future yield projections varied with area estimation methods, expansion status, and catchability assumptions and projected that expansion would delay the time required to restore optimal yields. These findings highlight that fishing ground expansion is a less efficient use of fishing area, excludes several more efficient gears and livelihoods, slows recovery, and does not guarantee sustainability, or high long-term employment or yields. Detecting these patterns required regular evaluation of multiple fisheries and fisheries' independent variables, long-term assessments of effort, area, and ecological production. Moreover, simple time series and future projection methods can promote recommendations that hide the resource overshoot dynamic caused by a misalignment and time lags between production and capture rate estimates.