Unprecedented and rapid changes are ongoing in northern high latitude, marine ecosystems, due to climate warming. Species distributions and abundances are changing, altering both ecosystem structure and dynamics. At the same time, human impacts are increasing. Less sea ice opens for the opportunity of more petroleum-related activities, shipping and tourism. Fisheries are moving into previously unfished habitats, targeting more species across more trophic levels. There is a need for ecosystem-based fisheries management (EBFM) and ecosystem-based management (EBM) to take the rapid, climate driven changes into account. Recently, there has been much development in qualitative, semi-quantitative, and quantitative scientific approaches to support EBFM and EBM. Here, we present some of these approaches, and discuss how they provide opportunities for advancing EBFM and EBM in one high-latitude system, namely the Barents Sea. We propose that advancing EBFM and EBM is more about adding tools to the toolbox than replacing tools, and to use the tools in coordinated efforts to tackle the increasing complexities in scientific support to management. Collaborative and participatory processes among stakeholders and scientists are pivotal for both scoping and prioritizing, and for efficient knowledge exchange. Finally, we argue that increasing uncertainty with increasing complexity is fundamental to decision making in EBFM and EBM and needs to be handled, rather than being a reason for inaction or irrelevance.
Carrying capacity models for aquaculture have increased in complexity over the last decades, partly because aquaculture growth, sustainability, and licensing are themselves extremely complex. Moreover, there is an asymmetric pattern to all these components, when considered from an international perspective, because of very different regulation and governance of the aquaculture sector in Asia, Europe, and America. Two case studies were used, from Long Island Sound in the United States, and Belfast Lough, in Europe, to examine the interactions between cultivated shellfish and other autochthonous benthic filter-feeders. The objective is to illustrate how such interactions can be incorporated in system-scale ecological models and analyzed from the perspective of ecological carrying capacity. Two different models are described, one based on equations that relate the filtration rate of the hard clam Mercenaria mercenaria to physiological and population factors and one based on a habitat-specific analysis of multiple species of benthic filter-feeders. Both types of models have relative advantages and challenges, and both were integrated in ecosystem modeling frameworks with substantial numbers of state variables representing physical and biogeochemical processes. These models were applied to (1) examine the relative role of the two components (cultivated and wild) in the filtration of particulate organic matter (both phytoplankton and organic detritus), (2) quantify the effect of wild species on harvest of cultivated organisms (eastern oyster and blue mussel), and (3) assess the role of organically extractive aquaculture and other filter-feeders on top–down control of eutrophication.
Gear selectivity and discards are important issues related to fisheries management but separately modelled. This work examines for the first time the overall size-selection pattern on the total amount of individuals of a species entering the trawl codend. An innovative approach was used based on modelling the escapement through the codend in the sea and the subsequently selection process by the fisher on the deck of the fishing vessel resulting into the discards and landings. Three different trawl codends and three species were investigated in the case study conducted. A dual sequential model accounting for both gear size-selectivity and the subsequent fisher-size-selectivity was applied, under the hypothesis that a fish entering the codend can follow a multinomial distribution with three probabilities, the escape, the discard and the landing probability, respectively. The model described the escape probability through the gear and the landing probability by the fisher as S-shaped curves leading to a bell-shaped curve for the discard probability affected by both gear and fisher selection. The model described well the experimental data in all cases. Sampling scheme of three compartments proved adequate. The model provides at the same time selectivity and discards parameters useful in fisheries management.
The appetite for ecosystem-based fisheries management (EBFM) approaches has grown, but the perception persists that implementation is slow. Here, we synthesize progress toward implementing EBFM in the United States through one potential avenue: expanding fish stock assessments to include ecosystem considerations and interactions between species, fleets, and sectors. We reviewed over 200 stock assessments and assessed how the stock assessment reports included information about system influences on the assessed stock. Our goals were to quantify whether and how assessments incorporated broader system-level considerations, and to explore factors that might contribute to the use of system-level information. Interactions among fishing fleets (technical interactions) were more commonly included than biophysical interactions (species, habitat, climate). Interactions within the physical environment (habitat, climate) were included twice as often as interactions among species (predation). Many assessment reports included ecological interactions only as background or qualitative considerations, rather than incorporating them in the assessment model. Our analyses suggested that ecosystem characteristics are more likely to be included when the species was overfished (stock status), the assessment is conducted at a science centre with a longstanding stomach contents analysis program, and/or the species life history characteristics suggest it is likely to be influenced by the physical environment, habitat, or predation mortality (short-lived species, sessile benthic species, or low trophic-level species). Regional differences in stomach contents analysis programs may limit the inclusion of predation mortality in stock assessments, and more guidance is needed on best practices for the prioritization of when and how biophysical information should be considered. However, our results demonstrate that significant progress has been made to use best available science and data to expand single-species stock assessments, particularly when a broad definition of EBFM is applied.
Aquatic ecosystems are under severe pressure. Human activities introduce an array of pressures that impact ecosystems and their components. In this study we focus on the aquatic domains of fresh, coastal and marine waters, including rivers, lakes and riparian habitats to transitional, coastal as well as shelf and oceanic habitats. In an environmental risk assessment approach, we identified impact chains that link 45 human activities through 31 pressures to 82 ecosystem components. In this linkage framework >22,000 activity-pressure-ecosystem component interactions were found across seven European case studies. We identified the environmental impact risk posed by each impact chain by first categorically weighting the interactions according to five criteria: spatial extent, dispersal potential, frequency of interaction, persistence of pressure and severity of the interaction, where extent, dispersal, frequency and persistence account for the exposure to risk (spatial and temporal), and the severity accounts for the consequence of the risk. After assigning a numerical score to each risk criterion, we came up with an overall environmental impact risk score for each impact chain. This risk score was analysed in terms of (1) the activities and pressures that introduce the greatest risk to European aquatic domains, and (2) the aquatic ecosystem components and realms that are at greatest risk from human activities. Activities related to energy production were relevant across the aquatic domains. Fishing was highly relevant in marine and environmental engineering in fresh waters. Chemical and physical pressures introduced the greatest risk to the aquatic realms. Ecosystem components that can be seen as ecotones between different ecosystems had high impact risk. We show how this information can be used in informing management on trade-offs in freshwater, coastal and marine resource use and aid decision-making.
Understanding the biogeochemical cycles and distribution of trace elements in the marine environment is one of the main challenges in chemical oceanography. We describe herein the trace metal composition of the uppermost surface ocean of various oceanographic regions (Arctic and Southern Oceans, subtropical Atlantic Ocean, and Mediterranean Sea). Our results show that trace metals in the top meter of the ocean are found in two clearly differentiated layers according to metal abundance and stoichiometry, namely the surface microlayer (SML) and its underlying subsurface water (SSW). Although metal concentrations in the subsurface dissolved fractions vary regionally and globally, it shows a singular metal stoichiometric signature. This work emphasizes the need to study of the SML as unique compartment to improve our understanding of the biogeochemical cycle of trace metals in the surface ocean, especially for metals, such as Pb, Fe and Cu, which are abundant in the SML.
Ecosystem based management (EBM) is an ocean management theory that examines an ecosystem holistically, accounting for both human uses and natural processes. EBM has gained popularity due to growing conflicts over ocean space, fueled by increasing demands for natural resources and a rising awareness for environmental values. EBM asserts that by scoping short-term natural resource exploitation to allow for the preservation of the ecosystem's core structure and function, sustainable long-term exploitation can be achieved. Therefore, determining the ecosystem's structure and function is a main tenet to EBM. To translate EBM theory to practice, important ecological areas, or “ecological hotspots,” are identified to understand the core ecosystem spaces that drive overall function. Marine Spatial Planning (MSP) is a process in which to operationalize EBM theory, including ecological hotspots. The literature has taken time to assess EBM from the theoretical perspective, however few studies exist that examine EBM-MSP interactions as EBM theory is translated into practice and secondly compare approaches across countries. This paper focuses on a comparative analysis of how ecological hotspots were (or are being) identified within two ecosystems, the Barents Sea and Gulf of Maine. The EBM ocean plans to be assessed are the Norwegian Barents Sea-Lofoten ocean management plan (BSMP) and the U.S. Northeast Ocean Plan (NEOP). It is found that the motivating factors that prompted the development of the BSMP and NEOP influenced when and how quickly ecological hotspots were determined. This paper aims to contribute to the discussion revolving around how EBM-MSP decision-making processes are operationalized.
There is large variation across countries regarding their use of marine protected areas (MPAs) for conservation or sustainable management purposes. This is the first in-depth econometric analysis that makes use of a large panel dataset to identify the key socio-economic and geographical factors that correlate strongly with the extent of MPA coverage. The findings provide strong evidence of an Environmental Kuznets Curve in the domain of MPAs ‒ i.e. MPA coverage (as a share of total territorial waters) initially declines as average income per capita rises, but then starts increasing above a relatively low threshold level of economic development. This also holds when using the Human Development Index of the United Nations Development Programme in place of the level of (real) GDP per capita. There is also consistent evidence suggesting that democracy and population density are strong (positive and negative respectively) correlates of MPA coverage.
Fisheries have historically focused on single-species management, but there is a global movement to incorporate ecosystem-based processes. Marine protected areas (MPAs) offer an important management tool for enhancing ecosystem structure and function. This study investigated whether a non-lethal indicator of trophic position (TP) could be used to evaluate fishery health in southern California MPAs. We hypothesized that a common predator, kelp bass (Paralabrax clathratus), would occupy a higher TP and smaller niche space inside MPAs than at fished reference sites, and that these patterns would be supported by trends in abundance and gut contents. Stable isotope analysis of nitrogen (δ15N) and carbon (δ13C) were used to estimate the TP and niche space of kelp bass (N = 125) collected inside and outside of four MPAs during summer 2016–2017. Although all MPA sites supported a significantly higher biomass of kelp bass than reference sites, there was no consistent pattern in TP and niche space inside versus outside of MPAs. Gut contents showed that exploitation of ephemeral pelagic foods may reduce localized effects of MPAs on prey availability for this species. Our findings suggest that MPAs will not have consistent impacts on food web dynamics for higher level generalist predators and that ecosystem-level responses to protection may vary across locations within a bioregion. These results emphasize the importance of accounting for site-specific differences in food web structure before applying ecosystem-based metrics to fishery management.
Sea-level change around southern Africa (southern Namibia, South Africa, southern Mozambique) since Termination I has been quantified using a variety of indicators. Existing and new data are reviewed to provide a baseline for future studies and identify key research needs and opportunities in the region. While the southern African records broadly agree with other far-field records, detailed Holocene records present as-yet unresolved discrepancies with glacial isostatic adjustment (GIA) model predictions. Two domains, the west coast and east coast are considered. Radiocarbon dated saltmarsh facies and marine shells in life position provide the basis for the west coast sea-level curve back to 9 ka BP. Given the age and elevation uncertainties, a Mid-Holocene highstand of +2 to +4 m is suggested between 7.3 and 6 ka BP, as are several Late Holocene oscillations of <1 m amplitude. On the east coast, fewer data are available for the Mid to Late Holocene (post 7 ka BP) compared to the west, but many submerged indicators are available back to 13 ka BP. Reappraisal of existing data suggests a sea-level curve similar to that of the west coast. In both instances, the resolution of existing sea-level index points is neither sufficient to accurately constrain the magnitude and timing of the peak highstand nor the existence of minor inferred subsequent oscillations. Between 13 and 7 cal ka BP chronological and geomorphological evidence (submerged shoreline complexes) suggest several alternating periods of slow and rapid sea-level change. Despite abundant data, the indicator resolution to quantify these changes remains elusive.