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Which management actions work best to prevent or halt overfishing and to rebuild depleted populations? A comprehensive evaluation of multiple, co-occurring management actions on the sustainability status of marine populations has been lacking. Here we compiled detailed management histories for 288 assessed fisheries from around the world (accounting for 45% of those with formal stock assessments) and used hierarchical time-series analyses to estimate effects of different management interventions on trends in stock status. Rebuilding plans, applied less commonly than other management measures (implemented at some point historically for 43% of stocks), rapidly lowered fishing pressure towards target levels and emerged as the most important factor enabling overfished populations to recover. Additionally, the ratification of international fishing agreements, and harvest control rules specifying how catch limits should vary with population biomass, helped to reduce overfishing and rebuild biomass. Notably, we found that benefits of management actions are cumulative—as more are implemented, stock status improves and predicted long-term catches increase. Thus, a broad suite of management measures at local, national and international levels appears to be key to sustaining fish populations and food production. Wise management is critical to sustaining fisheries. This study finds that rebuilding plans, ratification of international agreements and harvest control rules yield strong benefits and that these are cumulative.

Small pelagic fishes are used for human consumption, fishmeal and fish oil. They constitute 25% of global fish catch and have been of considerable conservation concern because of their intermediate position in aquatic food webs, often being a dominant dietary component of marine predators. This paper provides an overview of trends in abundance and fishing pressure on small pelagic fish stocks from single-species scientific assessments that constitute 60% of global small pelagic catch. While most individual stocks have exhibited wide variability in abundance (typical of small pelagics compared with other fish taxa), across stocks there has been remarkable stability in average fishing pressure and biomass since 1970. On average, since 1970, the biomass of assessed small pelagic stocks is estimated to have been slightly above the biomass that would produce maximum sustainable yield, but estimation of this quantity for highly fluctuating stocks is quite uncertain. There were significant differences among assessed regions, with the Mediterranean and Black Sea of greatest concern for high and growing fishing pressure. The 40% of global small pelagic fish catch not covered by single-species quantitative stock assessments since 1970 comes largely from Asia, where catches have continued to increase. At regional levels, the average abundance of assessed small pelagic fish is largely unrelated to average fishing pressure, which we argue results both from the portfolio effect, where numerous stocks fluctuate with little correlation in abundance, and from the short life span of small pelagics coupled with recruitment largely independent of spawning abundance. publishedVersion

Significance This article compiles estimates of the status of fish stocks from all available scientific assessments, comprising roughly half of the world’s fish catch, and shows that, on average, fish stocks are increasing where they are assessed. We pair this with surveys of the nature and extent of fisheries management systems, and demonstrate that where fisheries are intensively managed, the stocks are above target levels or rebuilding. Where fisheries management is less intense, stock status and trends are worse. We review evidence on the half of world fisheries that are not assessed or intensively managed and suggest their status is much worse than where fisheries are intensively managed., Marine fish stocks are an important part of the world food system and are particularly important for many of the poorest people of the world. Most existing analyses suggest overfishing is increasing, and there is widespread concern that fish stocks are decreasing throughout most of the world. We assembled trends in abundance and harvest rate of stocks that are scientifically assessed, constituting half of the reported global marine fish catch. For these stocks, on average, abundance is increasing and is at proposed target levels. Compared with regions that are intensively managed, regions with less-developed fisheries management have, on average, 3-fold greater harvest rates and half the abundance as assessed stocks. Available evidence suggests that the regions without assessments of abundance have little fisheries management, and stocks are in poor shape. Increased application of area-appropriate fisheries science recommendations and management tools are still needed for sustaining fisheries in places where they are lacking.

Many of the world's fisheries are unassessed, with little information about population status or risk of overfishing. Unassessed fisheries are particularly predominant in developing countries and in small-scale fisheries, where they are important for food security. Several catch-only methods based on time series of fishery catch and commonly available life-history traits have been developed to estimate stock status (defined as biomass relative to biomass at maximum sustainable yield: B/B-MSY). While their stock status performance has been extensively studied, performance of catch-only models as a management tool is unknown. We evaluated the extent to which a superensemble of three prominent catch-only models can provide a reliable basis for fisheries management and how performance compares across management strategies that control catch or fishing effort. We used a management strategy evaluation framework to determine whether a superensemble of catch-only models can reliably inform harvest control rules (HCRs). Across five simulated fish life histories and two harvest-dynamic types, catch-only models and HCR combinations reduced the risk of overfishing and increased the proportion of stocks above B-MSY compared to business as usual, though often resulted in poor yields. Precautionary HCRs based on fishing effort were robust and insensitive to error in catch-only models, while catch-based HCRs caused high probabilities of overfishing and more overfished populations. Catch-only methods tended to overestimate B/B-MSY for our simulated data sets. The catch-only superensemble combined with precautionary effort-based HCRs could be part of a stepping stone approach for managing some data-limited stocks while working towards more data-moderate assessment methods.

A systematic European Union (EU)-wide data framework for the collection of fisheries data in support of the EU Common Fisheries Policy (CFP) was first implemented in 2002. Since that time, EU data collection regulation has undergone 2 revisions in response to evolving policy needs. The European Commission’s Joint Research Centre (JRC) is responsible for conducting research and providing advice on fisheries management under the CFP, and since 2005 has worked closely with the Scientific, Technical and Economic Committee for Fisheries (STECF). JRC and STECF have an open data policy, and aggregated data submitted by EU member states in response to data calls issued under the provisions of the data collection regulation are published via the website of the STECF. This paper provides an overview of the fisheries data activities carried out by the JRC in support of and in collaboration with the STECF and discusses some of the benefits and drawbacks of such activities.

Fishery managers must often reconcile conflicting estimates of population status and trend. Superensemble models, commonly used in climate and weather forecasting, may provide an effective solution. This approach uses predictions from multiple models as covariates in an additional "superensemble" model fitted to known data. We evaluated the potential for ensemble averages and superensemble models (ensemble methods) to improve estimates of population status and trend for fisheries. We fit four widely applicable data-limited models that estimate stock biomass relative to equilibrium biomass at maximum sustainable yield (B/BMSY). We combined these estimates of recent fishery status and trends in B/BMSY with four ensemble methods: an ensemble average and three superensembles (a linear model, a random forest and a boosted regression tree). We trained our superensembles on 5,760 simulated stocks and tested them with cross-validation and against a global database of 249 stock assessments. Ensemble methods substantially improved estimates of population status and trend. Random forest and boosted regression trees performed the best at estimating population status: inaccuracy (median absolute proportional error) decreased from 0.42 -0.56 to 0.32 -0.33, rank-order correlation between predicted and true status improved from 0.02 - 0.32 to 0.44 - 0.48 and bias (median proportional error) declined from - 0.22 - 0.31 to - 0.12 - 0.03. We found similar improvements when predicting trend and when applying the simulation-trained superensembles to catch data for global fish stocks. Superensembles can optimally leverage multiple model predictions; however, they must be tested, formed from a diverse set of accurate models and built on a data set representative of the populations to which they are applied.

Most ecosystems are subject to both natural and human disturbances that can combine to influence populations and assemblages in complex ways. Assessing the relative influences and combined impacts of natural and human disturbance is crucial for managing human uses of ecosystems against the backdrop of their natural variability. We evaluated the separate and combined influences of disturbance from storm waves and disturbance associated with human trampling of rocky shores by conducting an experiment mimicking controlled levels of trampling at sites with different wave exposures, and before and after a major storm event in central California, USA. Results show that trampling and storm waves affected the same taxa and have comparable and additive effects on rocky shore assemblages. Both disturbance types caused significant reduction in percent cover of mussels and erect macroalgae, and resulted in significant re-organization of assemblages associated with these habitat-forming taxa. A single extreme storm event caused similar percent cover losses of mussels and erect macroalgae as did 6–12 months of trampling. Contrary to a predicted synergistic effect of trampling and storm damage, we found that impacts from each disturbance combined additively. Mussel beds in wave-exposed sites are more vulnerable to trampling impacts than algal beds at protected sites. Mussels and erect macroalgae recovered within five years after trampling stopped. These results suggest that impacts from local human use can be reversed in relatively short time frames, and that cumulative impacts can be reduced by setting recreational carrying capacities more conservatively when ecosystems are already exposed to frequent and/or intense natural disturbances.

According to the Common Fisheries Policy, all commercial fish stocks in the Mediterranean and Black Sea should be managed at MSY by 2015–2020. However, currently 95% of assessed stocks are overexploited and 73% of demersal species are not assessed. To explore the risk of overexploitation to un-assessed stocks, vulnerability scores were constructed using Productivity Susceptibility Analysis (PSA) for 151 Mediterranean demersal fish species. Out of 151 species, 58 displayed low vulnerability, 20 medium vulnerability, 25 high vulnerability and 48 were considered of major concern. More than half of stocks showed a risk of being overfished (termed “vulnerability”), greater than that of the stocks currently assessed in the Mediterranean Sea. Most of the cartilagineous fish fell into the high and major concern areas. The quality of data used for the PSA was scored and these scores could be used to improve future collection of data. Vulnerability scores are well correlated with IUCN red list classification. To rank the priority of commercial stocks still to be assessed, vulnerability scores were scaled with landings and mean price per stock. Eight of the top fifteen ranking stocks are currently not assessed. When the vulnerability of cartilaginous fish was tested against rate of decline estimated from trawl survey time-series, no strong correlation was found. The exploitation ratio (F/Fmsy) of assessed stocks was regressed, using generalized mixed models, against PSA scores and area and a significant relationship was found. Using this result, assessed stocks were used as a training set to predict the exploitation of un-assessed stocks. F/Fmsy was predicted for 151 species in 14 management areas (GSAs). The results over all areas is that 39 species-area combinations are exploited sustainably, all occurring in area 20 (Greece), while the remaining 2075 are exploited unsustainably with respect to Fmsy (F/Fmsy > 1). This prediction model, albeit after further refinement with more data and testing, could be used to predict exploitation ratio when no information on stock status is available. We predict that ≈98% of the unassessed demersal fish species are potentially overexploited in the evaluated areas. This makes it clear that strong management action will be required to achieve the targets of the Common Fisheries Policy in the next 1–5 years.

Demand for data-limited stock assessment methods is increasing, and new methods are being developed rapidly. One class of these methods requires only catch time series and, in some cases, information about life history or fishery characteristics, to estimate stock status. These catch-only methods (COMs) range from statistical models trained on data-rich stocks to mechanistic population models that make assumptions about changes in fishing effort. We review 11 COMs, comparing performance through application to data-rich stocks and simulated fisheries. The catch-only methods evaluated here produce imprecise and biased estimates of B/BMSY, especially for stocks that are lightly exploited. They were also generally poor classifiers of stock status. While no method performed best across all stocks, ensembles of multiple COMs generally performed better than individual COMs. We advocate for testing new COMs using this common platform. We also caution that performance in estimating stock status is not sufficient for gauging the usefulness of COMs in managing fisheries. Greater use of management strategy evaluation is needed before COMs can be considered a reliable tool for management.

The exploitation status of marine fisheries stocks worldwide is of critical importance for food security, ecosystem conservation, and fishery sustainability. Applying a suite of data-limited methods to global catch data, combined through an ensemble modeling approach, we provide quantitative estimates of exploitation status for 785 fish stocks. Fifty six percent (439 stocks) are below BMSY and of these, 261 are estimated to be below 80% of the BMSY level. While the 178 stocks above 80% of BMSY are conventionally considered “fully exploited”, stocks staying at this level for many years, forego substantial yield. Our results enable managers to consider more detailed information than simply a categorization of stocks as “fully” or “over” exploited. Our approach is reproducible, allows consistent application to a broad range of stocks, and can be easily updated as new data become available. Applied on an ongoing basis, this approach can provide critical, more detailed information for resource management for more exploited fish stocks than currently available. This article is protected by copyright. All rights reserved

The current fish stock assessment process in Europe can be very resource- and time-intensive. The scientists involved require a very particular set of skills, acquired over their career, drawing from biology, ecology, statistics, mathematical modelling, oceanography, fishery policy, and computing. There is a particular focus on producing a single “best” stock assessment model, but as fishery science advances, there are clear needs to address a range of hypotheses and uncertainties, from large-scale issues such as climate change to specific ones, such as high observation error on young hake. Key to our discussion is the use of the assessment for all frameworks to translate hypotheses into models. We propose a change to the current stock assessment procedure, driven by the use of model averaging to address a range of plausible hypotheses, where increased collaboration between the varied disciplines within fishery science will result in more robust advice., JRC.G.3-Maritime affairs

The current fish stock assessment process in Europe can be very resource- and time-intensive. The scientists involved require a very particular set of skills, acquired over their career, drawing from biology, ecology, statistics, mathematical modelling, oceanography, fishery policy, and computing. There is a particular focus on producing a single “best” stock assessment model, but as fishery science advances, there are clear needs to address a range of hypotheses and uncertainties, from large-scale issues such as climate change to specific ones, such as high observation error on young hake. Key to our discussion is the use of the assessment for all frameworks to translate hypotheses into models. We propose a change to the current stock assessment procedure, driven by the use of model averaging to address a range of plausible hypotheses, where increased collaboration between the varied disciplines within fishery science will result in more robust advice.

Information and understanding of fishing activities at sea are fundamental components of marine knowledge and maritime situational awareness. Such information is important to fisheries science, public authorities and policy makers. In this paper we introduce a first map at European scale of EU fishing activities extracted using Automatic Identification System (AIS) ship tracking data. The resulting map is a density of points that identify fishing activities. A measure of the reliability of such information is also presented as a map of coverage reception capabilities., Paper accepted for publication

The application of ecosystem-based management (EBM) in marine environments has been widely supported by scientists, managers, and policy makers, yet implementation of this approach is difficult for various scientific, political, and social reasons. A key, but often overlooked, challenge is how to account for multiple and varied human activities and ecosystem services and incorporate ecosystem-level thinking into EBM planning. We developed methods to systematically identify the natural and human components of a specific ecosystem and to qualitatively evaluate the strength of their interactions. Using the Gulf of Maine marine ecosystem as a case study, we show how these methods may be applied, in order to identify and prioritize the most important components to be included in an EBM plan – particularly the human activities that are the strongest drivers of ecosystem change and the ecosystem services most threatened by cumulative and indirect effects of these activities.

Design- and model-based approaches provide 2 distinct frameworks in which to analyse environmental impacts. While both approaches have been criticized to some extent, the possibility of modeling environmental variability with covariates in the analysis of structured sampling designs seems to have eluded the attention of environmental ecologists. We applied a beyond-BACI (before, after, control, impact) sampling design to a post-impact study on the effects of marinas on assem- blages of algae and invertebrates on rocky seashores at 2 locations in the NW Mediterranean. The 2 locations were on the opposite (northern and southern) sides of a promontory, about 30 km apart. A shore next to the marina and 3 reference shores were sampled at each location to obtain indepen- dent estimates of differences between disturbed and undisturbed conditions. An additional set of 3 shores were sampled at a location on the western coast to test whether structured spatial patterns around the promontory might confound the analysis of impact. Midshore and lowshore habitats were sampled on all shores. Multivariate and univariate analyses revealed differences between disturbed and reference assemblages mostly at one location in the midshore habitat. Analyses conducted on the lowshore data indicated that assemblages of marinas followed different temporal trajectories than reference shores consistently at the 2 locations. Spatial variability around the promontory was large, as indicated by significant linear and quadratic contrasts among all locations. When impacts were examined using either the geographic position of shores or their rank position around the promontory as a covariate, results did not differ from those of the original analyses. The present study highlights possible ways to overcome the dichotomy between design- and model-based approaches, namely that studies of impact can and should be examined at replicated locations whenever possible and that covariables can be included in the analysis of structured sampling designs to increase precision and accuracy in assessment of environmental impacts.

22 pages, 6 figures, 7 tables, supporting information http://dx.doi.org/10.1371/journal.pone.0119330.s001, We investigate long-term changes in the Mediterranean marine resources driving the trawl fisheries by analysing fishers' perceptions (Traditional Ecological Knowledge, TEK) throughout the Mediterranean Sea during the last 80 years. To this end, we conducted an extended set of interviews with experienced fishers that enabled us to classify species (or taxa) as 'decreasing' or 'increasing' both in terms of abundance, as well as average size in the catch. The aspect that most clearly emerged in all the investigated areas over time was the notable increase of fishing capacity indicators, such as engine power and fishing depth range. Atlantic mackerel, poor cod, scorpionfishes, striped seabream, and John Dory demonstrated a decreasing trend in the fishers' perceived abundance, while Mediterranean parrotfish, common pandora, cuttlefish, blue and red shrimp, and mullets gave indications of an increasing temporal trend. Although, as a rule, trawler captains did not report any cataclysmic changes (e.g. extinctions), when they were invited to estimate total catches, a clear decreasing pattern emerged; this being a notable finding taking into account the steep escalation of fishing efficiency during the past century. The overall deteriorating status of stocks in most Mediterranean regions calls for responsible management and design of rebuilding plans. This should include historical information accounting for past exploitation patterns that could help defining a baseline of fish abundance prior to heavy industrial fisheries exploitation. © 2015 Damalas et al., The data acquisition was supported by the European Commission through project EVOMED (“The 20th Century evolution of Mediterranean exploited demersal resources under increasing fishing disturbance and environmental change” (no MARE/2008/11: Lot 4)

9 pages, 3 figures, 4 tables, supplementary data http://icesjms.oxfordjournals.org/content/72/9/2600/suppl/DC1, Discarding of commercially important fish species in the bottom trawl fisheries in the northern Mediterranean Seawas investigated by soliciting the long-term recollections of fishers engaged or formerly engaged in such fisheries. The main aim of our investigationwas to describe the prevalence of discarding and its evolution over the past 70 years using information gathered through individual questionnaire-based interviews with fishers from ports in Spain, Italy, and Greece, following a standardized sampling protocol. Although it proved impossible to derive absolute estimates of the volume of discarded catches over the period investigated, we conclude that over the past 70 years, discarding as a practice has gradually increased in the northern Mediterranean trawl fisheries and has been accompanied by a shift in the species composition of the discarded catch. While discarding can occur for a number of reasons, our investigations indicate that discarding in the past was mostly driven by market demand, but recent legal and regulatory constraints have led to changes in fishing strategies and became a significant reason for discards, Data acquisition was supported by the European Commission through the EU project EVOMED (“The 20th Century evolution of Mediterranean exploited demersal resources under increasing fishing disturbance and environmental change”). European Commission, Directorate-General for Maritime Affairs and Fisheries. Open Call for Tenders n8 MARE/2008/11, Proposal for Lot 4, (Contract. N8 SI2 539097)

Sharks and rays’ abundance can decline considerably with fishing. Community changes, however, are more complex because of species interactions, and variable vulnerability and exposure to fishing. We evaluated long-term changes in the elasmobranch community of the Adriatic Sea, a heavily exploited Mediterranean basin where top-predators have been strongly depleted historically, and fishing developed unevenly between the western and eastern side. Combining and standardizing catch data from five trawl surveys from 1948– 2005, we estimated abundance trends and explained community changes using life histories, fish-market and effort data, and historical information.Weidentified a highly depleted elasmobranch community. Since 1948, catch rates have declined by .94% and 11 species ceased to be detected. The exploitation history and spatial gradients in fishing pressure explained most patterns in abundance and diversity, including the absence of strong compensatory increases. Ecological corridors and large-scale protected areas emerged as potential management options for elasmobranch recovery., JRC.G.4-Maritime affairs

10 pages, 4 figures, 4 tables, We conducted interviews of a representative sample of 106 retired fishers in Italy, Spain and Greece, asking specific questions about the trends they perceived in dolphin and shark abundances between 1940 and 1999 (in three 20 year periods) compared to the present abundance. The large marine fauna studied were not target species of the commercial fleet segment interviewed (trawl fishery). The fishers were asked to rank the perceived abundance in each period into qualitative ordinal classes based on two indicators: frequency of sightings and frequency of catches (incidental or intentional) of each taxonomic group. The statistical analysis of the survey results showed that both incidental catches and the sighting frequency of dolphins have decreased significantly over the 60+ years of the study period (except for in Greece due to the recent population increase). This shows that fishers' perceptions are in agreement with the declining population trends detected by scientists. Shark catches were also perceived to have diminished since the early 1940s for all species. Other long-lived Mediterranean marine fauna (monk seals, whales) were at very low levels in the second half of the 20th century and no quantitative data could be obtained. Our study supports the results obtained in the Mediterranean and other seas that show the rapid disappearance (over a few decades) of marine fauna. We show that appropriately designed questionnaires help provide a picture of animal abundance in the past through the valuable perceptions of fishers. This information can be used to complement scientific sources or in some cases be taken as the only information source for establishing population trends in the abundance of sensitive species, The data acquisition was supported by the European Commission through project EVOMED (“The 20th Century evolution of Mediterranean exploited demersal resources under increasing fishing disturbance and environmental change”, n° MARE/2008/11: Lot 4). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Coastal marine assemblages are shaped by interactions between physical factors, biological interactions, and almost ubiquitously, human impacts. Large-scale ma- nipulations 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 Mediter- ranean islands, Capraia and Giannutri, Italy. We hypothesized that fishing influences as- semblages 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.