Trait-based ecology merges evolutionary with classical population and community ecology and is a rapidly developing branch of ecology. It describes ecosystems as consisting of individuals rather than species, and characterizes individuals by few key traits that are interrelated through trade-offs. The fundamental rationale is that the spatio-temporal distribution of organisms and their functional role in ecosystems depend on their traits rather than on their taxonomical affiliation. The approach respects that interactions are between individuals, not between species or populations, and in trait-based models ecosystem structure emerges as a result of interactions between individuals and with the environments, rather than being prescribed. It offers an alternative to classical species-centric approaches and has the potential to describe complex ecosystems in simple ways and to assess the effects of environmental change on ecosystem structure and function. Here, we describe the components of the trait-based approach and apply it to describe and model marine ecosystems. Our description is illustrated with multiple examples of life in the ocean from unicellular plankton to fish.
In the Mediterranean Sea, the dominant type of fisheries is small-scale. Coastal communities remain dependent on fisheries for their income, some of them with limited potential for economic diversification. The top-down micro-management regime has proven ineffective to secure ecological and social sustainability as it lacks flexibility and adaptation to local and regional conditions. This paper explores the advantages of using a participatory approach and a bio-economic model to develop management scenarios in a high value small-scale shrimp trap fishery in Greece. Seeking active stakeholder involvement throughout the management process advanced the identification of management measures aiming at MSY, with high levels of acceptance from stakeholders. It also increased transparency and legitimacy of the proposed management measures and could be considered as a first step towards co-management and regionalization. The participatory approach undertaken could promote compliance and facilitate the transition to sustainable fishing, ensuring the viability of coastal communities and, thus, social sustainability.
Harmful algae can cause death in fish, shellfish, marine mammals, and humans, via their toxins or from effects associated with their sheer quantity. There are many species, which cause a variety of problems around north-west Europe, and the frequency and distribution of algal blooms have altered in the recent past. Species distribution modelling was used to understand how harmful algal species may respond in the future to climate change, by considering environmental preferences and how these may shift. Most distribution studies to date use low resolution global model outputs. In this study, high resolution, downscaled shelf seas climate projections for the north-west European shelf were nested within lower resolution global projections, to understand how the distribution of harmful algae may change by the mid to end of century. Projections suggest that the habitat of most species (defined by temperature, salinity, depth, and stratification) will shift north this century, with suitability increasing in the central and northern North Sea. An increase in occurrence here might lead to more frequent detrimental blooms if wind, irradiance and nutrient levels are also suitable. Prioritizing monitoring of species in these susceptible areas could help in establishing early-warning systems for aquaculture and health protection schemes.
Although aquaculture sometimes lessens the negative effects of fishing by lowering the need to capture wild animals and plants, some aquaculture practices still require the exploitation of wild populations. A largely overlooked case is the use of wild populations to provide seed to sea farms. Mussel farming in Northwest Spain involve the capture of thousands of tons of young mussels (0.5–2 cm long) from the nearby rocky intertidal every year to supply floating rafts. Despite its volume, the impact of this activity on other sessile organisms remains unassessed. To fill this gap in our knowledge, we monthly monitored the sessile intertidal assemblage of five protected and six exploited sites during the closed season in 2016 following a nested sampling plan. Like the by-catch typical of other fisheries, harvesting young mussels for aquaculture was detrimental to the abundance and diversity of the associated sessile assemblage not directly targeted by this activity. Coverage and richness were also significantly lowered by the exploitation of mussel seed, and the community structure of protected and exploited sites was significantly different. These differences continued until the next open season, suggesting that the closed season was too short for the recovery of the associated non-target sessile assemblage. Given the size of the local mussel industry, the incomplete recovery along the closed season implies that mussel aquaculture must be putting a sustained pressure on a sizeable portion of the rocky intertidal of Northwest Spain.
Marine fisheries are a significant source of protein for many human populations. In some locations, however, destructive fishing practices have negatively impacted the quality of fish habitat and reduced the habitat’s ability to sustain fish stocks. Improving the management of stocks that can be potentially damaged by harvesting requires improved understanding of the spatiotemporal dynamics of the stocks, their habitats, and the behavior of the harvesters. We develop a mathematical model for both a fish stock as well as its habitat quality. Both are modeled using nonlinear, parabolic partial differential equations, and density dependence in the growth rate of the fish stock depends upon habitat quality. The objective is to find the dynamic distribution of harvest effort that maximizes the discounted net present value of the coupled fishery-habitat system. The value derives both from extraction (and sale) of the stock and the provisioning of ecosystem services by the habitat. Optimal harvesting strategies are found numerically. The results suggest that no-take marine reserves can be an important part of the optimal strategy and that their spatiotemporal configuration depends both on the vulnerability of habitat to fishing damage and on the timescale of habitat recovery when fishing ceases.
No-take marine reserves are common strategies used in spatial fisheries management. There are at least four general objectives for marine reserve design: (1) maximizing conservation, (2) minimizing total reserve area, (3) maximizing reserve compactness, and (4) minimizing socioeconomic opportunity cost (e.g., fisheries revenue). A spatial optimization model was developed to solve for reserve placements under those four objectives, while evaluating the bioeconomic tradeoffs and potential gaps of a subset of bottomfish restricted fishing areas (BRFAs) for the Hawaiian bottomfish fishery. Optimized reserve placements with minimal opportunity costs had little overlap (< 9%) with the placements of the BRFAs, opportunity cost values 50–83% less than that of the BRFAs with 40–54% higher potential conservation value. When reserve placements were optimized to provide a maximal opportunity cost, solutions had up to 49% overlap with the BRFAs, highlighting a potential drawback of the BRFA system with respect to socioeconomic impacts. When opportunity cost was instead calculated as total area, the optimized placements also had considerable overlap (up to 42%) with the BRFAs, highlighting the importance of socioeconomic data to the reserve design process. The solutions that provided maximal reserve compactness may be the most pragmatic for a reserve design team with specific area and/or conservation targets, as these solutions produced compact reserve placements that best matched those targets at a minimal opportunity cost. This analysis emphasized the use of spatial optimization models to not only guide the reserve design process, but to highlight tradeoffs of conflicting fisheries objectives in reserve design.
Freshwater biodiversity is declining, despite national and international efforts to manage and protect freshwater ecosystems. Ecosystem-based management (EBM) has been proposed as an approach that could more efficiently and adaptively balance ecological and societal needs. However, this raises the question of how social and ecological objectives can be included in an integrated management plan. Here, we present a generic model-coupling framework tailored to address this question for freshwater ecosystems, using three components: biodiversity, ecosystem services (ESS), and a spatial prioritisation that aims to balance the spatial representation of biodiversity and ESS supply and demand. We illustrate this model-coupling approach within the Danube River Basin using the spatially explicit, potential distribution of (i) 85 fish species as a surrogate for biodiversity as modelled using hierarchical Bayesian models, and (ii) four estimated ESS layers produced by the Artificial Intelligence for Ecosystem Services (ARIES) platform (with ESS supply defined as carbon storage and flood regulation, and demand specified as recreation and water use). These are then used for (iii) a joint spatial prioritisation of biodiversity and ESS employing Marxan with Zones, laying out the spatial representation of multiple management zones. Given the transboundary setting of the Danube River Basin, we also run comparative analyses including the country-level purchasing power parity (PPP)-adjusted gross domestic product (GDP) and each country’s percent cover of the total basin area as potential cost factors, illustrating a scheme for balancing the share of establishing specific zones among countries. We demonstrate how emphasizing various biodiversity or ESS targets in an EBM model-coupling framework can be used to cost-effectively test various spatially explicit management options across a multi-national case study. We further discuss possible limitations, future developments, and requirements for effectively managing a balance between biodiversity and ESS supply and demand in freshwater ecosystems.
Resolutions of the United Nations General Assembly (UNGA) require states and competent authorities to protect vulnerable marine ecosystems (VMEs), ecologically important habitats in the deep sea that are considered to be especially at risk from anthropogenic disturbances such as fishing. The lack of data concerning the location and extent of VMEs poses a significant obstacle to their protection. Habitat suitability modeling is increasingly used in spatial management planning due to its ability to predict the distribution and niche of marine organisms based on limited input data. We generated broad-scale, medium-resolution (1 km2) ensemble models for ten VME indicator taxa within the New Zealand Exclusive Economic Zone and a portion of the South Pacific Regional Fishery Management Organisation (SPRFMO) convention area. Ensemble models were constructed using a weighted average of three habitat suitability model types: Boosted Regression Trees, Maximum Entropy, and Random Forest. All models performed well, with area under the curve scores above 0.9, and ensemble models marginally outperformed any of the individual modeling approaches. Highly suitable habitat for each VME indicator taxa was predicted to occur in relatively small areas throughout the region, typically associated with elevated seafloor features with steep slopes. Determining the spatial distribution of VME indicator taxa is critical for assessing the current and historical extent of bottom trawling impacts on benthic communities, and for supporting the improved spatial management of fisheries in the South Pacific Ocean. Given the additional threats of climate change and ocean acidification to VME indicator taxa throughout the deep sea, habitat suitability modeling is likely to play an increasing role in designing effective, long-term protection measures for cumulative impacts on VMEs.
Coral reef ecosystems provide many important services to society. Their importance is not only proved by their beauty but also because they provide food and livelihood for millions of people in communities around the world, especially in developing countries. This paper estimates the economic value of coral ecosystems and potential impacts of climate change and fishing activities on the loss of coral reefs in Nha Trang Bay, Vietnam. Economic valuation and bioeconomic approaches are applied to combine socioeconomic data and projections of coral reef cover based on the quantitative scenarios of sea surface temperature and fishing activity to articulate the potential economic consequences of future change in the coral reef. The loss in economic value of coral under climate change and fishing effort scenarios is estimated which ranges from US$27.78 to US$31.72 million annually. This result is useful for policy makers to draw conclusions for climate policy, biodiversity conservation, sustainable development, and priorities for further work.
Fisheries resources in the U.S. Gulf of Mexico (GoM) are under increasing pressure from both natural and anthropogenic stressors that have potentially broad effects on the ecosystem and introduce considerable uncertainty into management outcomes. To address these issues, more holistic, ecosystem-based tools are needed to inform decision-making. A Scoping Workshop with scientists, managers, and other stakeholders was held to identify and prioritize challenges in the GoM that could be addressed using ecosystem models, and how best to incorporate those models into the existing fisheries assessment and management framework. Challenges identified were associated with uncertainty in stock assessments, environmental stressors, multi-species reference points, invasive species, habitat effects, spatial management, and forage fisheries. Short-term priorities included those that address critical assumptions in stock assessments and inform imminent decision making, whereas long-term priorities were those associated with environmental stressors and novel management approaches. This information is intended to guide future ecosystem modeling efforts and help advance ecosystem based fisheries management in the region.