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6 pages, 5 figures, supporting information https://doi.org/10.1073/pnas.1900194116.-- All data reported in this paper are archived and publicly available at http://dataservices.gfz-potsdam.de/pik/showshort.php?id=escidoc:2956913., While the physical dimensions of climate change are now routinely assessed through multimodel intercomparisons, projected impacts on the global ocean ecosystem generally rely on individual models with a specific set of assumptions. To address these single-model limitations, we present standardized ensemble projections from six global marine ecosystem models forced with two Earth system models and four emission scenarios with and without fishing. We derive average biomass trends and associated uncertainties across the marine food web. Without fishing, mean global animal biomass decreased by 5% (±4% SD) under low emissions and 17% (±11% SD) under high emissions by 2100, with an average 5% decline for every 1 °C of warming. Projected biomass declines were primarily driven by increasing temperature and decreasing primary production, and were more pronounced at higher trophic levels, a process known as trophic amplification. Fishing did not substantially alter the effects of climate change. Considerable regional variation featured strong biomass increases at high latitudes and decreases at middle to low latitudes, with good model agreement on the direction of change but variable magnitude. Uncertainties due to variations in marine ecosystem and Earth system models were similar. Ensemble projections performed well compared with empirical data, emphasizing the benefits of multimodel inference to project future outcomes. Our results indicate that global ocean animal biomass consistently declines with climate change, and that these impacts are amplified at higher trophic levels. Next steps for model development include dynamic scenarios of fishing, cumulative human impacts, and the effects of management measures on future ocean biomass trends, Financial support was provided by the German Federal Ministry of Education and Research through ISI-MIP (Grant01LS1201A1), the European Union’s Horizon 2020 Research and Innovation Program (Grant 678193), and the Ocean Frontier Institute (Module G). We acknowledge additional financial support as follows: to H.K.L., W.W.L.C., and B.W. from the Natural Sciences and Engineering Research Council (NSERC) of Canada; to D.P.T. from the Kanne Rasmussen Foundation Denmark; to A.B.-B. from the NSERC Transatlantic Ocean Science and Technology Program; to W.W.L.C. and T.D.E. from the Nippon Foundation-Nereus Program; to E.D.G., M.C. and J. Steenbeek from the European Union’s Horizon 2020 Re-search and Innovation Program (Grants 682602 and 689518); to E.A.F., J.L.B., andT.R. from Commonwealth Scientific and Industrial Research Organization and the Australian Research Council; to N.B., L.B., and O.M. from the French Agence Nationale de la Recherche and Pôle de Calcul et de Données pour la Mer; and to S.J. from the UK Department of Environment, Food and Rural Affairs

Climate change is shifting the abundance and distribution of marine species with consequences for ecosystem functioning, seafood supply, management and conservation. Several approaches for future projection exist but these have never been compared systematically to assess their variability. We conducted standardized ensemble projections including 6 global fisheries and marine ecosystem models, forced with 2 Earth-system models and 4 emission scenarios in a fished and unfished ocean, to derive average trends and associated uncertainties. Without fishing, mean global animal biomass decreased by 5% (±4%) under low and 17% (±11%) under high emissions by 2100, primarily driven by increasing temperature and decreasing primary production. These climate-change effects were slightly weaker for larger animals and in a fished ocean. Considerable regional variation ranged from strong biomass increases in high latitudes to strong decreases in mid-low latitudes, with good model agreement on the direction of change but variable magnitude. Uncertainties due to differences among ecosystem or Earth-system models were similar, suggesting equal need for model improvement. Our ensemble projections provide the most comprehensive outlook on potential climate-driven ecological changes in the ocean to date. Realized future trends will largely depend on how fisheries and management adapt to these changes in a changing climate.

Marine legislation is becoming more complex and marine ecosystem-based management is specified in national and regional legislative frameworks. Shelf-seas community and ecosystem models (hereafter termed ecosystem models) are central to the delivery of ecosystem-based management, but there is limited uptake and use of model products by decision makers in Europe and the UK in comparison with other countries. In this study, the challenges to the uptake and use of ecosystem models in support of marine environmental management are assessed using the UK capability as an example. The UK has a broad capability in marine ecosystem modelling, with at least 14 different models that support management, but few examples exist of ecosystem modelling that underpin policy or management decisions. To improve understanding of policy and management issues that can be addressed using ecosystem models, a workshop was convened that brought together advisors, assessors, biologists, social scientists, economists, modellers, statisticians, policy makers, and funders. Some policy requirements were identified that can be addressed without further model development including: attribution of environmental change to underlying drivers, integration of models and observations to develop more efficient monitoring programmes, assessment of indicator performance for different management goals, and the costs and benefit of legislation. Multi-model ensembles are being developed in cases where many models exist, but model structures are very diverse making a standardised approach of combining outputs a significant challenge, and there is a need for new methodologies for describing, analysing, and visualising uncertainties. A stronger link to social and economic systems is needed to increase the range of policy-related questions that can be addressed. It is also important to improve communication between policy and modelling communities so that there is a shared understanding of the strengths and limitations of ecosystem models.

Model intercomparison studies in the climate and earth sciences communities have been crucial to build credibility and coherence for future projections. They have quantified variability among models, spurred model development, contrasted within- and among-model uncertainty, assessed model fits to historical data, and provided ensemble projections of future change under specified scenarios. Given the speed and magnitude of anthropogenic change in the marine environment, and consequent effects on food security, biodiversity, marine industries and society, the time is ripe for similar comparisons among models of fisheries and marine ecosystems. Here, we describe the Fisheries and Marine Ecosystem Model Intercomparison Project protocol version 1.0 (Fish-MIP v1.0), part of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP), a cross-sectoral network of climate impact modellers. Given the complexity of the marine ecosystem, this class of models has substantial heterogeneity of purpose, scope, theoretical underpinning, processes considered, parameterizations, resolution (grain size) and spatial extent. This heterogeneity reflects the lack of a unified understanding of the marine ecosystem, and implies that the assemblage of all models is more likely to include a greater number of relevant processes than is any single model. The current Fish-MIP protocol is designed to allow these heterogeneous models to be forced with common Earth System Model (ESM) CMIP5 outputs under prescribed scenarios for historic (from 1950s) and future (to 2100) time periods; it will be adapted to CMIP6 in future iterations. It also describes a standardized set of outputs for each participating Fish-MIP model to produce. This enables the broad characterization of differences between, and uncertainties within, models and projections when assessing climate and fisheries impacts on marine ecosystems and the services they provide. The systematic generation, collation and comparison of results from Fish-MIP will inform understanding of the range of plausible changes in marine ecosystems, and improve our capacity to define and convey strengths and weaknesses of model-based advice on future states of marine ecosystems and fisheries. Ultimately, Fish-MIP represents a step towards bringing together the marine ecosystem modelling community to produce consistent ensemble medium- and long-term projections of marine ecosystems.

Eddy, T.D. ... et al.-- 14 pages, 6 figures, supporting Information, Since the 1950s, invertebrate fisheries catches have rapidly expanded globally to more than 10 million tonnes annually, with twice as many target species, and are now significant contributors to global seafood provision, export, trade and local livelihoods. Invertebrates play important and diverse functional roles in marine ecosystems, yet the ecosystem effects of their exploitation are poorly understood. Using 12 ecosystem models distributed worldwide, we analysed the trade-offs of various invertebrate fisheries and their ecosystem effects as well as ecological indicators. Although less recognized for their contributions to marine food webs, our results show that the magnitude of trophic impacts of invertebrates on other species of commercial and conservation interest is comparable with those of forage fish. Generally, cephalopods showed the strongest ecosystem effects and were characterized by a strong top-down predatory role. Lobster, and to a lesser extent, crabs, shrimp and prawns, also showed strong ecosystem effects, but at lower trophic levels. Benthic invertebrates, including epifauna and infauna, also showed considerable ecosystem effects, but with strong bottom-up characteristics. In contrast, urchins, bivalves, and gastropods showed generally lower ecosystem effects in our simulations. Invertebrates also strongly contributed to benthic–pelagic coupling, with exploitation of benthic invertebrates impacting pelagic fishes and vice versa. Finally, on average, invertebrates produced maximum sustainable yield at lower levels of depletion (~45%) than forage fish (~65%), highlighting the need for management targets that avoid negative consequences for target species and marine ecosystems as a whole, Key financial support for this project was provided by the Lenfest Ocean Program with a grant to HKL. MC was partially funded by the European Commission through the Marie Curie Career Integration Grant Fellowships – PCIG10-GA-2011-303534 – to the BIOWEB project and by the Spanish National Program Ramon y Cajal. VC acknowledges support from NSERC, Canada. SM gratefully acknowledges the support provided by Defra project M1228 ‘Fizzyfish’

Lauria, V., Vaz, S., Martin, C. S., Mackinson, S., and Carpentier, A. 2011. What influences European plaice (Pleuronectes platessa) distribution in the eastern English Channel? Using habitat modelling and GIS to predict habitat utilization. – ICES Journal of Marine Science, 68: 1500–1510. Conservation of fish habitat requires knowledge of how spatial distributions of species are related to environmental factors. Habitat modelling and mapping are useful in predicting species–environment relationships. Species abundance is modelled as a function of environmental parameters to understand species habitat utilization better. The influence of environmental factors on plaice (Pleuronectes platessa) distribution was investigated for two life stages and over two seasons. Generalized linear modelling and quantile regression modelling were used to relate the relative abundance of (juvenile and adult) fish to environmental predictors (seawater temperature, salinity, water column depth, bed-shear stress, and sediment type) in autumn and summer. The resulting regression parameters were used to map preferential and potential habitat distributions within a geographic information system. Models were evaluated by comparing predicted against observed abundances. Seabed sediment type was the main significant predictor of plaice preferential and potential habitats, whereas other factors did not show such a clear influence. The results contribute to a better understanding of the spatial ecology of the species.

An ecosystem model of the western English Channel ecosystem in 1994 was used to explore the effects of the use of a fishing policy optimization routine on profits, number of jobs and ecosystem structure. The optimization for single objective led to the specialization of the fishing fleet, with some fleet types being almost excluded. The profits and mainly the job optimizations led to big changes in the ecosystem structure, with loss of diversity, but the overall biomass of all vertebrate groups represented in the model increased considerably. For the objective focusing on ecosystem structure, there was an increase in biodiversity, with many long-lived groups predicted to increase, although the overall vertebrate biomass suffered just a small increase. An “ideal” mixed policy configuration was found when slightly greater weight was given to ecosystem structure than was given to profits and jobs. This scenario led to an overall reduction in effort but also to increased profits and biodiversity, while keeping the number of jobs at the same level as the baseline estimates. The results of the optimizations showed that the average trophic level of the catches is quite resistant to changes in the underlying system structure. On the other hand, despite the high level of aggregation of the model structure, a biodiversity index estimated by the model presented large changes as a function of the weights placed on the single policy functions, reflecting the changes in the system structure. The output of the application of the fishing optimization presented here should be considered in qualitative rather than in quantitative terms as an aid and part contribution to the complicated discussions on future long term management actions. Nonetheless it points to an overall reduction in fishing capacity, an objective widely accepted within the scientific community, while keeping the fishery in a profitable state.

To explore the contributions that fishing, trophic interactions and plankton production make to explanations of the observed variation of higher trophic (principally fish) levels in the western English Channel ecosystem, Ecosim simulations were run from 1973 to 1999 using the most complete data set yet assembled. The results indicate that a bottom-up mechanism plays an important role in the system production. Inclusion of a primary producer biomass forcing term, estimated from empirical data, improved the goodness of fit of the model estimates to the available biomass data by about 25% compared to fitting using only the series of fishing mortalities. Model fitting was further improved by changing the so-called vulnerability parameters, causing an overall improvement of 62% in explained variation. Incorporating the new vulnerability values, the model was used to estimate a primary production anomaly function to replace the primary producer biomass forcing in driving the model simulations. In this scenario, the model estimated a series of values for primary producer abundance that approximated the empirical data, but gave lower estimates than were observed towards the end of the period. This version also gave a better fitting to the zooplankton abundance data and generally improved the fitting to all functional groups.

Modelling is perceived as being one of the only tools available to address the new agenda of ecosystem management. However, little is currently understood with regard to the influence of model structure and configuration on predictions and hence management recommendations. In the present study we used a detailed Ecopath with Ecosim (EwE) model of the Barents Sea to test the impacts of food-web aggregation and the removal of weak linkages. Aggregation of a 41-compartment food-web to 27 and 16 compartment systems, greatly affected system properties (e.g. connectance, system omnivory, ascendancy), and also influenced dynamic stability. Highly aggregated models recovered more quickly following disturbances (a pulse of increased fishing pressure) compared to the original disaggregated model. Models aggregated with emphasis placed on particular parts of the food-web (fish, marine-mammals or invertebrates) exhibited marked differences in system indices, despite having the same number of compartments. Models in which invertebrates and basal materials (primary producers and detritus) were heavily aggregated proved particularly resilient to system disturbances. Models focusing on marine-mammals (but in which all other groups were heavily aggregated) also proved very resilient to disturbance, partly due to the slow turnover rates and low biomasses of these top-predatory consumers compared to all other functional groups in the model. Thus, the psychology and decisions of scientists constructing the model can greatly affect its performance and predictions. The Pareto c index is proposed, as a useful measure of skewness towards weak trophic links in food-web models. The 41-compartment ‘control’ model exhibited the highest Pareto c value, and hence was most skewed. Removal of weak links from the food-web, either by eliminating fluxes below a certain threshold or by random-sampling the diet-composition matrix, resulted in models with much lower connectance and Pareto c values. Such models were inherently less stable than the 41-compartment ‘control’ model. Recovery to within 10% of starting values took longer when links had been removed, and the magnitude of fluctuations following a disturbance was also increased. Our findings infer a clear contradiction. Aggregated models possessed fewer weak links but recovered from a disturbance more quickly than disaggregated models (i.e., they were more stable). By contrast, food-webs from which weak links were specifically removed were the least stable of all the models tested. Thus whether weak links are removed through ‘lumping’ or ‘chopping’ seems to have very different system consequences.

In communities sharing a common energy source, the energetic equivalence hypothesis predicts that numerical abundance (N) scales with body mass (M )a sM )0.75 . However, in size-structured food webs all individuals do not share a common energy source, and the energy available (E ) to larger individuals is constrained by inefficient energy transfer through the food chains that support them. This is expected to lead to steeper scalings of N with M. Here, we formalize and test an existing model for predicting abundance–body mass scaling, where the decline in E with M is calculated from the mean predator–prey body mass ratio (from size-based nitrogen stable isotope analysis) and trophic transfer efficiency. We show that the steep predicted scalings of abundance and body mass (N scales as M )1.2 , B scales as M )0.2 ) in a marine food web are consistent with empirical estimates and can be attributed to the small predator–prey body mass ratio (106 : 1). As a previous study has shown that environmental stability may favour low predator–prey mass ratios and long food chains, we predict that steeper abundance–body mass relationships will be found in more stable environments.

We present the first acoustic observations of predator-prey interactions between fin whales and herring. The school dynamics and predation events of Norwegian spring-spawning herring (Clupea harengus) in a cold front area (about 125 km 2 ) in the Norwegian Sea in April were quantified. Data from high-resolution sonar tracking of herring schools combined with echosounder data were integrated with pelagic-trawl samples. A total of 44 herring schools were each observed for an average of 34.8 min. Altogether, 184 behavioural events were recorded, with an event occurring every 8.3 min on average. Intra-school events (compression, reorganization, ring, pseudopodium, elongate, diving, surfacing) were observed every 15.3 min and inter-school events (approach, join, leave, split) every 22.9 min. We observed 17 fin whales (Balaenoptera physalus), six Atlantic white-sided dolphins (Lagenorhynchus acutus) and five killer whales (Orcinus orca) within the experimental area. Predator events occurred every 91 min on average. Of these marine mammals only fin whales swimming alone or in small groups (2-5 ind.) were observed to attack herring. Attacks from fin whales were observed every 170 min. They strongly influenced the density, shape and structure of the herring schools. Large fish such as cod (Gadus morhua) and saithe (Pollachius virens) preying on herring in coastal areas were not caught in the pelagic trawl or detected by acoustics. Herring schools were on average large (987 m 2 ), dense, swam at depth (148 m) and had a moderate swimming speed (1.1 body lengths per second), reflecting a risk-averse, anti-predator behaviour to marine mammals. We discuss differences in schooling dynamics, anti-predator behaviour, attack frequency and predation risk between herring attacked by fin whales in an offshore area and herring attacked by gadoid predators closer to the coast in a similar study in May.

Methods of assessing the structure and function of food webs are needed to provide a basis for assessing large-scale direct (e.g. fisheries) and indirect (e.g. climate change) effects of human activities on marine ecosystems. We present a simple synthesis of the complex structure and function of a real marine food web, based on analyses of body size distributions, production-body size relationships and trophic level-body size relationships. We show how size-based estimates of production, species richness and trophic level (from nitrogen stable isotope analysis) can be used to quantify trophic transfer efficiency, mean predator-prey body-mass ratios and the mean ratio of the number of predator to prey species in marine food webs. We applied these methods to the central North Sea, and estimated transfer efficiencies of 3.7 to 12.4%, a mean predator-prey body-mass ratio of 109:1 and a mean ratio of the number of predator to prey species of 0.34. We conducted sensitivity analyses to show how differences in the fractionation of δ 15 N and changes in the slope of the rela- tionship between production and δ 15 N affected our predictions. Our estimates of transfer efficiency and mean predator-prey body-mass ratios are similar to those obtained by costly and labour-intensive diet- and ecosystem-modelling studies. Coupled analyses of size and trophic structure may provide a method for validating ecosystem models and assessing human impacts on marine ecosystems.

Using the Celtic Sea and the North Sea as case studies, we show that a fleet-based approach is the pathway to implement an effective ecosystem approach to fisheries management (EAFM) in European seas. First, a diagnostic on the health of each ecosystem is proposed based on: the reconstruction of long time-series of catch, the analysis of mean indicators or stocks trajectories derived from ICES stock assessment results, and the analysis of ecosystem indicators. Then, we present a fleet-based synthesis using indicators of both the ecological impact and the economic performances of the major fleets operating within each ecosystem. In particular, assessment diagrams show whether each fleet segment, on average, sustainably exploits the stocks. Although results are preliminary due to the poor quality of available data, the analysis shows that simple indicators can be estimated and clearly highlight contrasts between fleet segments. Such an approach contributes to the evolution from a stock-based to a fleet based management, which reflects the ecological, economical and social pillars of the sustainable development of fisheries., JRC.G.4-Maritime affairs