CONICET | Buscador de Institutos y Recursos Humanos

In the absence of a historical baseline, no-take marine reserves can provide a reference to the unfished condition in exploited species of limited mobility. This study documents the recovery of the spiny lobster Palinurus elephas population within a large no-take marine reserve (MR) in the northwestern Mediterranean, and uses it as a baseline to assess stock status in exploited grounds in the region.Lobster indices of density and biomass within the MR continued to increase after 25 years of protection, a period close to the species? lifespan. Catch per unit effort (CPUE) in terms of weight more than doubled from 2000 to 2015 inside the reserve while the increase of CPUE in numbers was only 20%. This faster increase in biomass reflected individual growth and spillover of predominantly smaller lobsters to adjacent fished grounds. A highly depleted status of the exploited populations was inferred from the demographic structure and CPUEs inside and outside the MR, with fishery:MR ratios and relative reproductive potential per unit area less than 0.05. In the MR the size-class of maximum egg production increased over time, in contrast to the stable and smaller sizes responsible for egg production in the fished areas. At present, the contribution of small size classes (below the 90 mm CL minimum landing size) to the overall egg production is only 1.5% in the MR while it reaches 30% in the fished areas. Total mortality estimated from recent size compositions assuming equilibrium was from three to four times higher in the fished areas than inside the MR, resulting in a reduction in predicted spawning potential per recruit to close to 20% of the unfished level. This experiment, albeit limited due to lack of replication and plausible confounding effects of environmental variability, emphasizes the value of long-term no-take areas as reference laboratories for investigating fishing effects.