Historical exploitation of the Mediterranean Sea and the absence of rigorous baselines makes it difficult to evaluate the current health of the marine ecosystems and the efficacy of conservation actions at the ecosystem level. Here we establish the first current baseline and gradient of ecosystem structure of nearshore rocky reefs at the Mediterranean scale. We conducted underwater surveys in 14 marine protected areas and 18 open access sites across the Mediterranean, and across a 31-fold range of fish biomass (from 3.8 to 118 g m−2). Our data showed remarkable variation in the structure of rocky reef ecosystems. Multivariate analysis showed three alternative community states: (1) large fish biomass and reefs dominated by non-canopy algae, (2) lower fish biomass but abundant native algal canopies and suspension feeders, and (3) low fish biomass and extensive barrens, with areas covered by turf algae. Our results suggest that the healthiest shallow rocky reef ecosystems in the Mediterranean have both large fish and algal biomass. Protection level and primary production were the only variables significantly correlated to community biomass structure. Fish biomass was significantly larger in well-enforced no-take marine reserves, but there were no significant differences between multi-use marine protected areas (which allow some fishing) and open access areas at the regional scale. The gradients reported here represent a trajectory of degradation that can be used to assess the health of any similar habitat in the Mediterranean, and to evaluate the efficacy of marine protected areas.

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A standard, universally useful classification scheme for deepwater habitats needs to be established so that descriptions of these habitats can be accurately and efficiently applied among scientific disciplines. In recent years many marine benthic habitats in deep water have been described using geophysical and biological data. These descriptions can vary from one investigator to another, which makes it difficult to compare habitats and associated biological assemblages among geographic regions. Using geophysical data collected with a variety of remote sensor systems and in situ biological and geologic observations, we have constructed a classification scheme that can be used in describing marine benthic habitats in deep water. 0 1999 Ifremer / CNRS / IRD / Editions scientifiques et medicales Elsevier SAS habitat / universal classification / benthic I fisheries management Resume .-Une classification des habitats benthiques profonds. Un systeme de classification des habitats benthiques profonds, pour avoir valeur de reference g&r&ale, doit pouvoir etre mis en pratique avec precision et efficacite dans les disciplines scientifiques. Ces dernieres an&es, les habitats marins benthiques profonds ont tte decrits a partir de dontrees geophysiques et biologiques ; les descriptions varient d'un chercheur a l'autre, rendant la comparaison difficile entre les habitats et les populations de differentes regions geographiques. Des donnees geophysiques obtenues par plusieurs systemes de detection a distance, et des observations biologiques et geologiques in situ, ont permis d'etablir une classification qui est proposee pour decrire les habitats marins benthiques en eau profonde. 0 1999 Ifremer / CNRS / IRD / Editions scientifiques et medicales Elsevier SAS habitat I classification universelle I benthique I gestion des pecheries

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Worldwide, chronic overfishing has depleted populations of large predatory reef fishes and caused unexpected, top-down changes in coral reef ecosystems. Groupers are especially susceptible to overexploitation, because they aggregate to reproduce at specific locations and times. An understanding of the spatial dynamics of these fishes is critical for fisheries management and conservation. However, movements and migration dynamics of endangered reef fishes are poorly known. We show, using acoustic telemetry, that Nassau groupers Epinephelus striatus exhibit highly synchronised migration to spawning sites, despite their otherwise solitary habits. Reproductive adults leave their individual territories in shallow waters near the winter full moons, and migrate to the same spawning site up to 4 times yr -1. At the spawning site, a remarkable population-wide depth change occurs within an hour as individuals dive to a maximum depth of 255 m. Our results greatly expand the previously known migration frequency and depth range of this species, and reveal an unexpected yet predictable complexity of adult fish migration between habitats. Effective conservation of this threatened species requires that deeper reefs and the timing of migration events be incorporated into fisheries management plans.

Meta-analyses of field studies have shown that biomass, density, species richness, and size of organisms protected by no-take marine reserves generally increase over time. The magnitude and timing of changes in these response variables, however, vary greatly and depend upon the taxonomic groups protected, size and type of reserve, oceanographic regime, and time since the reserve was implemented. We conducted collaborative, fishery-independent surveys of fishes for seven years in and near newly created marine protected areas (MPAs) in central California, USA. Results showed that initially most MPAs contained more and larger fishes than associated reference sites, likely due to differences in habitat quality. The differences between MPAs and reference sites did not greatly change over the seven years of our study, indicating that reserve benefits will be slow to accumulate in California’s temperate eastern boundary current. Fishes in an older reserve that has been closed to fishing since 1973, however, were significantly more abundant and larger than those in associated reference sites. This indicates that reserve benefits are likely to accrue in the California Current ecosystem, but that 20 years or more may be needed to detect significant changes in response variables that are due to MPA implementation. Because of the high spatial and temporal variability of fish recruitment patterns, long-term monitoring is needed to identify positive responses of fishes to protection in the diverse set of habitats in a dynamic eastern boundary current. Qualitative estimates of response variables, such as would be obtained from an expert opinion process, are unlikely to provide an accurate description of MPA performance. Similarly, using one species or one MPA as an indicator is unlikely to provide sufficient resolution to accurately describe the performance of multiple MPAs.

Marine Protected Areas (MPAs) are being implemented worldwide, yet there are few cases where managers make specific predictions of the response of previously harvested populations to MPA implementation. Such predictions are needed to evaluate whether MPAs are working as expected, and if not, why. This evaluation is necessary to perform adaptive management, identifying whether and when adjustments to management might be necessary to achieve MPA goals. Using monitoring data and population models, we quantified expected responses of targeted species to MPA implementation and compared them to monitoring data. The model required two factors to explain observed responses in MPAs: (a) pre‐MPA harvest rates, which can vary at local spatial scales, and (b) recruitment variability before and after MPA establishment. Low recruitment years before MPA establishment in our study system drove deviations from expected equilibrium population size distributions and introduced an additional time lag to response detectability. Synthesis and applications. We combined monitoring data and population models to show how (a) harvest rates prior to Marine Protected Area (MPA) implementation, (b) variability in recruitment, and (c) initial population size structure determine whether a response to MPA establishment is detectable. Pre‐MPA harvest rates across MPAs plays a large role in MPA response detectability, demonstrating the importance of measuring this poorly known parameter. While an intuitive expectation is for response detectability to depend on recruitment variability and stochasticity in population trajectories after MPA establishment, we address the overlooked role of recruitment variability before MPA establishment, which alters the size structure at the time of MPA establishment. These factors provide MPA practitioners with reasons whether or not MPAs may lead to responses of targeted species. Our overall approach provides a framework for a critical step of adaptive management.

Bays and estuaries play important roles in the life history of leopard sharks Triakis semifasciata, yet these coastal environments are among those most impacted by human activity. To better understand habitat use, spatial associations, and ecological roles of leopard sharks in estuarine environments, movements of leopard sharks were studied in Elkhorn Slough, California, USA. A total of 21 female leopard sharks (78 to 140 cm total length) were tagged with acoustic transmitters and tracked from August 2003 to February 2005. Eight sharks were manually tracked for 20 to 71.5 h, and 13 sharks were monitored for 4 to 280 d using an array of acoustic receivers. Female leopard sharks exhibited a high degree of fidelity to Elkhorn Slough. The distribution of tagged sharks changed seasonally and was likely associated with changes in temperature, salinity, and dissolved oxygen. Sharks used the area that comprises Elkhorn Slough National Estuarine Research Reserve (ESNERR) extensively throughout the year, but especially during spring and summer. When sharks occupied ESNERR, their habitat use was tidally influenced, with sharks using low intertidal mudflats extensively when available. Sharks using the main channel tended to remain in subtidal habitats at all tidal levels. These results suggest that efforts to protect important leopard shark habitats in bays and estuaries should focus on preserving and restoring intertidal mudflats.