The deep sea plays a critical role in global climate regulation through uptake and storage of heat and carbon dioxide. However, this regulating service causes warming, acidification and deoxygenation of deep waters, leading to decreased food availability at the seafloor. These changes and their projections are likely to affect productivity, biodiversity and distributions of deep‐sea fauna, thereby compromising key ecosystem services. Understanding how climate change can lead to shifts in deep‐sea species distributions is critically important in developing management measures. We used environmental niche modelling along with the best available species occurrence data and environmental parameters to model habitat suitability for key cold‐water coral and commercially important deep‐sea fish species under present‐day (1951–2000) environmental conditions and to project changes under severe, high emissions future (2081–2100) climate projections (RCP8.5 scenario) for the North Atlantic Ocean. Our models projected a decrease of 28%–100% in suitable habitat for cold‐water corals and a shift in suitable habitat for deep‐sea fishes of 2.0°–9.9° towards higher latitudes. The largest reductions in suitable habitat were projected for the scleractinian coral Lophelia pertusa and the octocoral Paragorgia arborea, with declines of at least 79% and 99% respectively. We projected the expansion of suitable habitat by 2100 only for the fishes Helicolenus dactylopterus and Sebastes mentella (20%–30%), mostly through northern latitudinal range expansion. Our results projected limited climate refugia locations in the North Atlantic by 2100 for scleractinian corals (30%–42% of present‐day suitable habitat), even smaller refugia locations for the octocorals Acanella arbuscula and Acanthogorgia armata (6%–14%), and almost no refugia for P. arborea. Our results emphasize the need to understand how anticipated climate change will affect the distribution of deep‐sea species including commercially important fishes and foundation species, and highlight the importance of identifying and preserving climate refugia for a range of area‐based planning and management tools.

Using a bioenergetic and allometric approach, we developed multispecies trophodynamic models of the marine community of northern and central Patagonia in the southwestern South Atlantic Ocean that included hake (Merluccius hubbsi), squid (Illex argentinus), anchovy (Engraulis anchoita), and South American sea lions (Otaria flavescens). We used these to explore the effects of model structure and parameter uncertainty on predictions of the effects of different management regimes using continuation and bifurcation analysis. We considered five different functional responses and used the Akaike Information Criterion for model selection. The best models involved laissez-faire Holling Type III-shaped functional responses and the worst one corresponded to the Ecosim form. These models showed many similar behaviours but also showed marked differences in some exploitation scenarios. This suggests that using a single model structure as the basis for managing these stocks could lead to misleading, and potentially dangerous, conclusions.

The Northwest Atlantic marine ecosystem off Newfoundland and Labrador, Canada, has been commercially exploited for centuries. Although periodic declines in various important commercial fish stocks have been observed in this ecosystem, the most drastic changes took place in the early 1990s when the ecosystem structure changed abruptly and has not returned to its previous configuration. In the Northwest Atlantic, food web dynamics are determined largely by capelin (Mallotus villosus), the focal forage species which links primary and secondary producers with the higher trophic levels. Notwithstanding the importance of capelin, the factors that influence its population dynamics have remained elusive. We found that a regime shift and ocean climate, acting via food availability, have discernible impacts on the regulation of this population. Capelin biomass and timing of spawning were well explained by a regime shift and seasonal sea ice dynamics, a key determinant of the pelagic spring bloom. Our findings are important for the development of ecosystem approaches to fisheries management and raise questions on the potential impacts of climate change on the structure and productivity of this marine ecosystem.

The United Nations General Assembly Resolution 61/105, concerning sustainable fisheries in the marine ecosystem, calls for the protection of vulnerable marine ecosystems (VME) from destructive fishing practices. Subsequently, the Food and Agriculture Organization (FAO) produced guidelines for identification of VME indicator species/taxa to assist in the implementation of the resolution, but recommended the development of case-specific operational definitions for their application. We applied kernel density estimation (KDE) to research vessel trawl survey data from inside the fishing footprint of the Northwest Atlantic Fisheries Organization (NAFO) Regulatory Area in the high seas of the northwest Atlantic to create biomass density surfaces for four VME indicator taxa: large-sized sponges, sea pens, small and large gorgonian corals. These VME indicator taxa were identified previously by NAFO using the fragility, life history characteristics and structural complexity criteria presented by FAO, along with an evaluation of their recovery trajectories. KDE, a non-parametric neighbour-based smoothing function, has been used previously in ecology to identify hotspots, that is, areas of relatively high biomass/abundance. We present a novel approach of examining relative changes in area under polygons created from encircling successive biomass categories on the KDE surface to identify “significant concentrations” of biomass, which we equate to VMEs. This allows identification of the VMEs from the broader distribution of the species in the study area. We provide independent assessments of the VMEs so identified using underwater images, benthic sampling with other gear types (dredges, cores), and/or published species distribution models of probability of occurrence, as available. For each VME indicator taxon we provide a brief review of their ecological function which will be important in future assessments of significant adverse impact on these habitats here and elsewhere.

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Introduction 153Living marine resource management context, history and background 154The fisheries 154The ecosystems 155Implementation of ecosystem-based approaches in living marine resource management 156Habitat closures and marine protected areas 157Models to provide tactical and strategic management advice 157Addressing questions on groundfish carrying capacity 159Directly examining pairwise species interactions 160 AbstractThe northwest Atlantic has had a notable history of living marine resource (LMR) exploitation. There have been calls for evaluating and improving approaches to manage those resources as stocks have undergone sequential depletion, with some dramatic instances of stock declines. The need for more holistic ecosystem-based approaches to manage LMRs has been increasingly recognized as part of these calls, along with the recognition that there are broader issues to consider when managing a fishery. We discuss some of the major efforts to this end which are extant among our institutions. We emphasize current initiatives to implement ecosystem-based fisheries management in the northwest Atlantic, with a focus on how advice based on the natural sciences supports an ecosystem-based approach. We present this information as a case study within a rich historical context of fisheries science and management.

Ecosystem-based fisheries management (EBFM) emphasizes sustainability at multiple levels of organization beyond single target species. Therefore, biological reference points (BRPs) for aggregated groups are required, which optimize yields while preventing overexploitation of individual species. We evaluate the tradeoffs between yield and biodiversity objectives for a wide range of aggregation strategies using multispecies surplus production models and comparing 2 simulated fish communities. We simulated population trajectories with an operating model detailing predation and competitive interactions for all individual species within each community, and with additional stochastic environmental variability for one community. Species trajectories were then aggregated by functional feeding guild, taxonomy, habitat association, size class, and at the entire community level. We estimated production parameters and BRPs (e.g. maximum sustainable yield, MSY) using a simple assessment model applied to each aggregated time series, then we applied the MSY fishing rates to each simulated community as alternative fishing strategies and compared equilibrium biomass and yield under each strategy. We were able to define multi-species reference points to meet both yield and biodiversity objectives across full system, taxonomic, habitat, feeding, and size-based aggregations. Species complexes were best able to meet both objectives when species with broadly similar productivity, environmental sensitivity and species interactions were aggregated into the complex. The impacts of simulated environmental variability on BRPs were substantial for certain species and aggregates, so including the combined impacts of environmental variation and species interactions in precautionary reference points appears critical to EBFM.

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