Applying an integrated approach to coastal marine habitat mapping in the north-western United Arab Emirates.

Habitat mapping is essential for the management and conservation of coastal marine habitats. However, accurate and up-to-date habitat maps are rarely available for the marine realm. In this study, we mapped the coastal marine habitats of >400 km of coastline in the north-western United Arab Emirates (UAE) using a combination of data sources including remote sensing, extensive ground-truthing points, local expert knowledge and existing information. We delineated 17 habitats, including critical habitats for marine biodiversity such as coral reefs and mangroves, and previously unreported oyster beds and deep seagrasses. This innovative approach was able to produce a coastal marine habitat map with an overall accuracy of 77%. The approach allowed for the production of a spatial tool well-suited for the needs of environmental management and conservation in a previously data-deficient area of the United Arab Emirates.

Small-sized and well-enforced Marine Protected Areas provide ecological benefits for piscivorous fish populations worldwide.

Many piscivorous fish species are depleted and/or threatened around the world. Marine Protected Areas (MPAs) are tools for conservation and fisheries management, though there is still controversy regarding the best design for increasing their ecological effectiveness. Here, on the basis of a weighted meta-analytical approach, we have assessed the effect of 32 MPAs, distributed worldwide, on the biomass and density of piscivorous fishes. We analysed the MPA features and the biological, commercial and ecological characteristics of fishes that may affect the response of species to protection. We found a positive effect on the biomass and density of piscivores inside MPAs. This effect was stronger for the biomass of medium-sized fishes (in relation to the maximum size reported for the species) and the density of large and gregarious species. The size of the no-take zone had a significant negative impact on both response variables and differed according to the level of enforcement, with smaller no-take zones having higher levels of enforcement. Thus, MPAs help to protect piscivorous fish species, with smaller, but well enforced reserves being more effective for the protection of the local populations of piscivorous fishes throughout the world.

Diversity of settlement-stage reef fishes captured by light-trap in a tropical south-west Atlantic Ocean coastal reef system.

This study reports the results of 5 years of monitoring reef fish post-larvae using light traps in the Bay of Tamandaré, north-east Brazil. An annotated checklist of pre-settlement fish species, their frequency of occurrence and taxonomic characteristics are provided. In total, 4,422 post-larval fishes belonging to 36 families, 56 genera and 76 species were captured. The most species-rich families were Carangidae (7), Lutjanidae (6) and Pomacentridae (4), while the families Gerreidae (30.47%), Holocentridae (16.54%), Blenniidae (12.01%), Labrisomidae (8.36%), Lutjanidae (8.29%) and Acanthuridae (5.95%) were the most abundant. This is the first study of the taxonomic diversity and assemblage structure of settlement-stage reef fishes in the tropical south-west Atlantic Ocean. Although a few common species were not captured due to selectivity of light traps, the composition and taxonomic diversity of this first collection suggests that light traps are useful for studies of the early life history of a wide range of pre-settlement reef fishes.

Author Correction: Ecological effects of full and partial protection in the crowded Mediterranean Sea: a regional meta-analysis.

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Effect of marine protected areas on distinct fish life-history stages.

The role of Marine Protected Areas on distinct life stages of Mediterranean reef fish species (classified on the basis of their economic value and mobility categories) was assessed in a network of marine reserves in SE Spain. Only abundance and biomass of adult of both commercial and demersal species were positively affected by protection. Gradients across reserve boundaries (as a clue to the occurrence of spillover) were observed for fish abundance but not for biomass, indicating a protected fish assemblage with a predominance of small-sized individuals. Also, post-larvae of commercial species were negatively related to protected zones. Active selection of settlement preferred habitats, larval accumulation favoured by the geomorphological configuration of the coast or mixed effects has been proposed as possible explanations. Juveniles showed high spatial variability resulting in a lack of response to fishing protection measures. We highlight the need of including early life stages and overall suitable habitats for them when designing MPA networks due to the crucial importance of these stages to successful fulfillment of MPA objectives.

The "Tracked Roaming Transect" and distance sampling methods increase the efficiency of underwater visual censuses.

Underwater visual census (UVC) is the most common approach for estimating diversity, abundance and size of reef fishes in shallow and clear waters. Abundance estimation through UVC is particularly problematic in species occurring at low densities and/or highly aggregated because of their high variability at both spatial and temporal scales. The statistical power of experiments involving UVC techniques may be increased by augmenting the number of replicates or the area surveyed. In this work we present and test the efficiency of an UVC method based on diver towed GPS, the Tracked Roaming Transect (TRT), designed to maximize transect length (and thus the surveyed area) with respect to diving time invested in monitoring, as compared to Conventional Strip Transects (CST). Additionally, we analyze the effect of increasing transect width and length on the precision of density estimates by comparing TRT vs. CST methods using different fixed widths of 6 and 20 m (FW3 and FW10, respectively) and the Distance Sampling (DS) method, in which perpendicular distance of each fish or group of fishes to the transect line is estimated by divers up to 20 m from the transect line. The TRT was 74% more time and cost efficient than the CST (all transect widths considered together) and, for a given time, the use of TRT and/or increasing the transect width increased the precision of density estimates. In addition, since with the DS method distances of fishes to the transect line have to be estimated, and not measured directly as in terrestrial environments, errors in estimations of perpendicular distances can seriously affect DS density estimations. To assess the occurrence of distance estimation errors and their dependence on the observer's experience, a field experiment using wooden fish models was performed. We tested the precision and accuracy of density estimators based on fixed widths and the DS method. The accuracy of the estimates was measured comparing the actual total abundance with those estimated by divers using FW3, FW10, and DS estimators. Density estimates differed by 13% (range 0.1-31%) from the actual values (average = 13.09%; median = 14.16%). Based on our results we encourage the use of the Tracked Roaming Transect with Distance Sampling (TRT+DS) method for improving density estimates of species occurring at low densities and/or highly aggregated, as well as for exploratory rapid-assessment surveys in which divers could gather spatial ecological and ecosystem information on large areas during UVC.

Ecological effects of full and partial protection in the crowded Mediterranean Sea: a regional meta-analysis.

Marine protected areas (MPAs) are a cornerstone of marine conservation. Globally, the number and coverage of MPAs are increasing, but MPA implementation lags in many human-dominated regions. In areas with intense competition for space and resources, evaluation of the effects of MPAs is crucial to inform decisions. In the human-dominated Mediterranean Sea, fully protected areas occupy only 0.04% of its surface. We evaluated the impacts of full and partial protection on biomass and density of fish assemblages, some commercially important fishes, and sea urchins in 24 Mediterranean MPAs. We explored the relationships between the level of protection and MPA size, age, and enforcement. Results revealed significant positive effects of protection for fisheries target species and negative effects for urchins as their predators benefited from protection. Full protection provided stronger effects than partial protection. Benefits of full protection for fish biomass were only correlated with the level of MPA enforcement; fish density was higher in older, better enforced, and -interestingly- smaller MPAs. Our finding that even small, well-enforced, fully protected areas can have significant ecological effects is encouraging for "crowded" marine environments. However, more data are needed to evaluate sufficient MPA sizes for protecting populations of species with varying mobility levels.

Warming-related shifts in the distribution of two competing coastal wrasses.

Warming induces organisms to adapt or to move to track thermal optima, driving novel interspecific interactions or altering pre-existing ones. We investigated how rising temperatures can affect the distribution of two antagonist Mediterranean wrasses: the 'warm-water' Thalassoma pavo and the 'cool-water' Coris julis. Using field surveys and an extensive database of depth-related patterns of distribution of wrasses across 346 sites, last-decade and projected patterns of distribution for the middle (2040-2059) and the end of century (2080-2099) were analysed by a multivariate model-based framework. Results show that T. pavo dominates shallow waters at warmest locations, where C. julis locates deeper. The northernmost shallow locations are dominated by C. julis where T. pavo abundance is low. Projections suggest that the W-Mediterranean will become more suitable for T. pavo whilst large sectors of the E-Mediterranean will be unsuitable for C. julis, progressively restricting its distribution range. These shifts might result in fish communities' re-arrangement and novel functional responses throughout the food-web.