Marine reserve more sustainable than gear restriction in maintaining long-term coral reef fisheries yields

Abstract

The long-term consequences of managing overfished fisheries through either gear restrictions or closures are among the many dilemmas facing small-scale fisheries managers. To evaluate long-term outcomes, fishing effort and catch were measured from 1995 to 2019 in two districts in Kenya, one that established a marine reserve in 1991 and another that eliminated destructive small-meshed drag nets beginning in 2001. Stock biomass in the 12 studied landing sites were below multispecies maximum sustainable yield (MMSY) and effort declined in all sites, indicating overfishing. Both interventions showed positive responses in catch per unit effort (CPUE) trends that indicated successful management but the changes were more sustained in the closure-adjacent than the gear-restricted landing sites. For example, total per-area yields in the gear-restricted sites declined steadily to an equilibrium that was 30% below the predicted MMSY. In contrast, and despite the low stock levels, closure-adjacent landing sites maintained yields near MMSY over the full time series. This is likely due to an increase in fish recovery rates by ~42% from an r of 0.23 to an r of 0.34 in the presence of a closure. The study suggests that closures that occupy ~30% of the nearshore fishing grounds could prevent suboptimal yields and fisheries collapse in nearshore East African reefs.