Aitor Forcada

Marine reserves: fish life history and ecological traits matter.

Marine reserves are assumed to protect a wide range of species from deleterious effects stemming from exploitation. However, some species, due to their ecological characteristics, may not respond positively to protection. Very little is known about the effects of life history and ecological traits (e.g., mobility, growth, and habitat) on responses of fish species to marine reserves. Using 40 data sets from 12 European marine reserves, we show that there is significant variation in the response of different species of fish to protection and that this heterogeneity can be explained, in part, by differences in their traits. Densities of targeted size-classes of commercial species were greater in protected than unprotected areas. This effect of protection increased as the maximum body size of the targeted species increased, and it was greater for species that were not obligate schoolers. However, contrary to previous theoretical findings, even mobile species with wide home ranges benefited from protection: the effect of protection was at least as strong for mobile species as it was for sedentary ones. Noncommercial bycatch and unexploited species rarely responded to protection, and when they did (in the case of unexploited bentho-pelagic species), they exhibited the opposite response: their densities were lower inside reserves. The use of marine reserves for marine conservation and fisheries management implies that they should ensure protection for a wide range of species with different life-history and ecological traits. Our results suggest this is not the case, and instead that effects vary with economic value, body size, habitat, depth range, and schooling behavior.

Evaluación de los efectos del anclaje de embarcaciones sobre pradera de Posidonia oceanica (L.) en dos localidades mediterráneas

Posidonia oceanica seagrass meadows has been evaluated in two localities off Alicante Coast (Spain), Tabarca Island and Moraira, submitted to a high anchoring pressure. In spite of the great heterogeneity at small scale, it was observed that anchoring produced an erosion of the meadow that caused a decrease in the density and covering and an increase of the dead Posidonia and the alteration index. When we compare our results with previous data at Tabarca Island it is observed that the regression of the meadow has not increased during the last 13 years. This may indicate that the erosion produced by anchoring at this locality has been compensated by the natural recovering of the meadow.