Projections of the impacts of gear-modification on the recovery of fish catches and ecosystem function in an impoverished fishery

Abstract

The regulation of fishing gear is a widely accepted fisheries management solution that requires further research to improve the chances of achieving sustainable yields, maintaining ecological integrity, and assisting fishers to escape from poverty. Fishing traps are a good candidate for modification because they are used widely, represent one of the most profitable gears, and often catch key species known to promote ecological resilience. The ecological and economic implications of modifying fishing traps with escape slots were examined in a heavily fished and poor artisanal Kenyan fishery. Catches of fish from traps with four escape slot sizes (2, 4, 6, and 8cm,) were examined for differences in the catch rates and composition and to calibrate a simulation model. The simulation model was used to predict how the ecological and economic outcomes will change as the standing stock responds to the new size selectivity of the fishing traps. The results suggest a fishery's wide implementation of the 2cm escape slots could provide an immediate benefit to the ecosystem by reducing the catch of juvenile fishes and algal browsers, which could help avoid or reverse coral-macroalgal phase shifts that can reduce reef biodiversity. However, the model predicts a decline in per trap profits in the first year that the 2cm escape slot is implemented. This period would be followed by profitability increasing by a factor of 1.6 and 2.2 in the second year for the 2cm and 4cm escape slots respectively. Sequential implementation of 2cm slots followed by 4cm slots in the fourth year reduces the total economic cost of implementing the 4cm slots by 34%. Consequently, sequential implementation of these traps is suggested as a potential way to simultaneously conserve key ecosystem functions and reduce poverty.