Non-linear response of catch rates to increasing salinity levels in a small-scale fishery

Abstract Gear and catch diversification can provide natural insurance to fishers by stabilising catch rates, thanks to the differential response of fish species to varying environmental conditions. The effectiveness of diversification, however, may be diminished if there is a threshold above which compensatory changes are weakened and species abundance tends to move in the same direction. We analyse this hypothesis using data from an open-access artisanal fishery in an estuarine ecosystem, located in a Colombian Biosphere. Reserve. We find evidence of a threshold in salinity levels in the 25–30 g kg −1 range for most gears employed in the fishery. Below the threshold, catch diversification stabilises the mean catch rate, but above it, catch rates decline. The evidence of a threshold defining a high salinity conditions regime calls for the adoption of adaptive fishery management strategies, as well as social protection mechanisms for vulnerable fishers.