Abstract. 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 sizeclasses 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.

Coastal marine assemblages are shaped by interactions between physical factors, biological interactions, and almost ubiquitously, human impacts. Large‐scale manipulations of human access replicated over a range of physical and biological conditions can generate insights over the processes shaping marine assemblages. We examined the relative roles of human impacts and hydrographic conditions on assemblages of shallow (3–10 m depth) rocky reefs by comparing no‐take reserves with fishing areas occurring in gradients of exposure of the coastline to dominant winds and waves around two Mediterranean islands, Capraia and Giannutri, Italy. We hypothesized that fishing influences assemblages directly by reducing populations of target fish species, and indirectly by reducing predation on sea urchins, intensifying herbivory, and causing “barrens” of encrusting coralline algae. We examined how the possible effects of fishing varied with physical exposure of the coastline. The composition of fish assemblages differed significantly between sites within no‐take reserves and fished reference sites. Abundances and sizes of predatory fishes targeted by local fisheries were greater in no‐take reserves than in fished areas. Sea urchin densities, the extent of coralline barrens, and the structure of the algal and invertebrate benthic assemblages showed clear variation associated with exposure of the coastline to dominant winds and waves, but weak effects of protection from human use. Densities of the black sea urchin Arbacia lixula were significantly greater along the windward than along the leeward sides of the islands, and were positively correlated with the extent of coralline barrens. In contrast, the purple sea urchin Paracentrotus lividus was more abundant along the leeward sides of islands and showed indirect responses to protection at Giannutri, where purple sea urchins tended to have greater densities at fished than at protected sites. Protection from fishing influenced fish assemblages directly, and benthic assemblages indirectly, but the latter effect was observed only at sites with lower physical exposure. Indirect effects of fishing and recovery of assemblages within marine protected areas through cascading trophic interactions are likely to vary depending on local physical conditions and on the characteristics of species that are locally dominant.

Extreme climate events produce simultaneous changes to the mean and to the variance of climatic variables over ecological time scales. While several studies have investigated how ecological systems respond to changes in mean values of climate variables, the combined effects of mean and variance are poorly understood. We examined the response of low-shore assemblages of algae and invertebrates of rocky seashores in the northwest Mediterranean to factorial manipulations of mean intensity and temporal variance of aerial exposure, a type of disturbance whose intensity and temporal patterning of occurrence are predicted to change with changing climate conditions. Effects of variance were often in the opposite direction of those elicited by changes in the mean. Increasing aerial exposure at regular intervals had negative effects both on diversity of assemblages and on percent cover of filamentous and coarsely branched algae, but greater temporal variance drastically reduced these effects. The opposite was observed for the abundance of barnacles and encrusting coralline algae, where high temporal variance of aerial exposure either reversed a positive effect of mean intensity (barnacles) or caused a negative effect that did not occur under low temporal variance (encrusting algae). These results provide the first experimental evidence that changes in mean intensity and temporal variance of climatic variables affect natural assemblages of species interactively, suggesting that high temporal variance may mitigate the ecological impacts of ongoing and predicted climate changes.

Understanding the extent to which natural assemblages withstand changes in the regime of disturbance has considerable practical and theoretical interest. In this paper we examine the separate and interactive effects of intensity, temporal variation, and spatial extent of disturbance on temporal variance in assemblages of algae and invertebrates of rocky shores in the northwest Mediterranean. Temporal variation of disturbance is a predictor variable in the experiment, while temporal variance in abundance and number of taxa and in structure of assemblages are response variables. Multivariate analyses detected a positive relationship between intensity of disturbance and temporal variance in the structure of assemblages, while temporal variation of disturbance elicited the opposite effect. Univariate analyses conducted on the most abundant taxa revealed idiosyncratic patterns, while temporal variance in mean number of taxa was greatly reduced by disturbance, with no distinction among levels of intensity, temporal variation, or spatial extent. These outcomes suggest caution in interpreting the results of experiments in which intensity and temporal variation of disturbance cannot be separated. Distinguishing between these traits of disturbance may be key to predicting the ecological consequence of environmental fluctuations, including those expected under modified climate scenarios.