During their migrations, marine predators experience varying levels of protection and face many threats as they travel through multiple countries’ jurisdictions and across ocean basins. Some populations are declining rapidly. Contributing to such declines is a failure of some international agreements to ensure effective cooperation by the stakeholders responsible for managing species throughout their ranges, including in the high seas, a global commons. Here we use biologging data from marine predators to provide quantitative measures with great potential to inform local, national and international management efforts in the Pacific Ocean. We synthesized a large tracking data set to show how the movements and migratory phenology of 1,648 individuals representing 14 species—from leatherback turtles to white sharks—relate to the geopolitical boundaries of the Pacific Ocean throughout species’ annual cycles. Cumulatively, these species visited 86% of Pacific Ocean countries and some spent three-quarters of their annual cycles in the high seas. With our results, we offer answers to questions posed when designing international strategies for managing migratory species.
Planning for marine areas, from coastal to open-ocean regions, is being developed worldwide to foster sustainable ocean management and governance. Over the past decades, significant progress has been made by governments in their thinking about marine spatial planning (MSP). MSP is globally widespread and a topic of increasing importance in the scientific and policy realms. It is currently under development in almost 70 countries, encompassing six continents and four ocean basins. Despite its acceptance and use, development and implementation of MSP still faces a myriad of present and future, conceptual and practical challenges, some of them being more striking and widespread. Here, we highlight seven major challenges that need to be properly addressed so that MSP can truly contribute to a sustainable use of the world's oceans. These include, among others, shortcomings in political and institutional frameworks, stakeholder engagement, encompassing human and social dimensions in MSP, balancing economic development and marine ecosystem conservation, and adapting to global environmental change.
Climate change is an immediate and future threat to food security globally. The consequences for fisheries and agriculture production potential are well studied, yet the possible outcomes for aquaculture (that is, aquatic farming)—one of the fastest growing food sectors on the planet—remain a major gap in scientific understanding. With over one-third of aquaculture produced in marine waters and this proportion increasing, it is critical to anticipate new opportunities and challenges in marine production under climate change. Here, we model and map the effect of warming ocean conditions (Representative Concentration Pathway scenario 8.5) on marine aquaculture production potential over the next century, based on thermal tolerance and growth data of 180 cultured finfish and bivalve species. We find heterogeneous patterns of gains and losses, but an overall greater probability of declines worldwide. Accounting for multiple drivers of species growth, including shifts in temperature, chlorophyll and ocean acidification, reveals potentially greater declines in bivalve aquaculture compared with finfish production. This study addresses a missing component in food security research and sustainable development planning by identifying regions that will face potentially greater climate change challenges and resilience with regards to marine aquaculture in the coming decades. Understanding the scale and magnitude of future increases and reductions in aquaculture potential is critical for designing effective and efficient use and protection of the oceans, and ultimately for feeding the planet sustainably.
Fishing intensity and selectivity patterns affect ecosystem structure and fisheries yield, the 2 fundamental performance measures in the ecosystem approach to fisheries. We used a simple multispecies predation model to explore the effect of alternative fishing strategies on a 3‑trophic-level food chain. Fishing strategies included highly selective fishing, nonselective fishing, and balanced harvesting that harvests all species at an instantaneous fishing mortality rate either proportional to intrinsic population growth rate or proportional to current population growth rate. The results showed that harvesting species at higher trophic levels has a low impact on total biomass but results in very low yields and severe impacts on trophic structure. Selectively harvesting species at the bottom of the food chain reduces the biomass of all fish, results in high yields, and is the only strategy that maintains unfished trophic structure. Non-selective fishing produces high total yield, but can cause extinction of fish at high trophic levels, and severely alters the trophic structure. Balanced harvest strategies produce higher total yield than harvesting species only at the bottom of the food chain, and have a smaller impact on trophic structure than selectively harvesting the top predator or nonselective fishing, but cannot fully maintain trophic structure. While these findings from a very simple model can provide insight into results from more complex models, analysis of sensitivity to structural assumptions in such simple models will be required to shed further light on the dynamic consequences of fishing across multiple trophic levels.
The response of coastal wetlands to sea-level rise during the twenty-first century remains uncertain. Global-scale projections suggest that between 20 and 90 per cent (for low and high sea-level rise scenarios, respectively) of the present-day coastal wetland area will be lost, which will in turn result in the loss of biodiversity and highly valued ecosystem services1,2,3. These projections do not necessarily take into account all essential geomorphological4,5,6,7 and socio-economic system feedbacks8. Here we present an integrated global modelling approach that considers both the ability of coastal wetlands to build up vertically by sediment accretion, and the accommodation space, namely, the vertical and lateral space available for fine sediments to accumulate and be colonized by wetland vegetation. We use this approach to assess global-scale changes in coastal wetland area in response to global sea-level rise and anthropogenic coastal occupation during the twenty-first century. On the basis of our simulations, we find that, globally, rather than losses, wetland gains of up to 60 per cent of the current area are possible, if more than 37 per cent (our upper estimate for current accommodation space) of coastal wetlands have sufficient accommodation space, and sediment supply remains at present levels. In contrast to previous studies1,2,3, we project that until 2100, the loss of global coastal wetland area will range between 0 and 30 per cent, assuming no further accommodation space in addition to current levels. Our simulations suggest that the resilience of global wetlands is primarily driven by the availability of accommodation space, which is strongly influenced by the building of anthropogenic infrastructure in the coastal zone and such infrastructure is expected to change over the twenty-first century. Rather than being an inevitable consequence of global sea-level rise, our findings indicate that large-scale loss of coastal wetlands might be avoidable, if sufficient additional accommodation space can be created through careful nature-based adaptation solutions to coastal management.
During the planning phase the efficacy of different strategies to manage marine resources should ultimately be assessed by their potential impact, or ability to make a difference to ecological and social outcomes. While community‐based and systematic approaches to establishing marine protected areas have their strengths and weaknesses, comparisons of their effectiveness often fail to explicitly address potential impact. Here, we predict conservation impact to compare recently implemented community‐based marine reserves in Tonga to a systematic configuration specifically aimed at maximizing impact. Boosted regression tree outputs indicated that fishing pressure accounted for ∼24% of variation in target species biomass. We estimate that the community‐based approach provides 84% of the recovery potential of the configuration with the greatest potential impact. This high potential impact results from community‐based reserves being located close to villages, where fishing pressure is greatest. These results provide strong support for community‐based marine management, with short‐term benefits likely to accrue even where there is little scope for systematic reserve design.
Manta and devil rays are filter-feeding elasmobranchs that are found circumglobally in tropical and subtropical waters. Although relatively understudied for most of the Twentieth century, public awareness and scientific research on these species has increased dramatically in recent years. Much of this attention has been in response to targeted fisheries, international trade in mobulid products, and a growing concern over the fate of exploited populations. Despite progress in mobulid research, major knowledge gaps still exist, hindering the development of effective management and conservation strategies. We assembled 30 leaders and emerging experts in the fields of mobulid biology, ecology, and conservation to identify pressing knowledge gaps that must be filled to facilitate improved science-based management of these vulnerable species. We highlight focal research topics in the subject areas of taxonomy and diversity, life history, reproduction and nursery areas, population trends, bycatch and fisheries, spatial dynamics and movements, foraging and diving, pollution and contaminants, and sub-lethal impacts. Mobulid rays remain a poorly studied group, and therefore our list of important knowledge gaps is extensive. However, we hope that this identification of high priority knowledge gaps will stimulate and focus future mobulid research.
Oil spill response (OSR) in the Arctic marine environment conducted as part of operational planning and preparedness supporting exploration and development is most successful when knowledge of the ecosystem is readily available and applicable in an oil spill risk assessment framework. OSR strategies supporting decision-making during the critical period after a spill event should be explicit about the environmental resources potentially at risk and the efficacy of OSR countermeasures that best protect sensitive and valued resources. At present, there are 6 prominent methods for spill impact mitigation assessment (SIMA) in the Arctic aimed at supporting OSR and operational planning and preparedness; each method examines spill scenarios and identifies response strategies best suited to overcome the unique challenges posed by polar ecosystems and to minimize potential long-term environmental consequences. The different methods are grounded in classical environmental risk assessment and the net environmental benefit analysis (NEBA) approach that emerged in the 1990s after the Exxon Valdez oil spill. The different approaches share 5 primary assessment elements (oil physical and chemical properties, fate and transport, exposure, effects and consequence analysis). This paper highlights how the different Arctic methods reflect this common risk assessment framework and share a common need for oil spill science relevant to Arctic ecosystems. An online literature navigation portal, developed as part of the 5-year Arctic Oil Spill Response Technologies Joint Industry Programme, complements the different approaches currently used in the Arctic by capturing the rapidly expanding body of scientific knowledge useful to evaluating exposure, vulnerability and recovery of the Arctic ecosystem after an oil spill.
This study assesses vessel-noise exposure levels for Southern Resident Killer Whales (SRKW) in the Salish Sea. Kernel Density Estimation (KDE) was used to delineate SRKW summer core areas. Those areas were combined with the output of a regional cumulative noise model describing sound level variations generated by commercial vessels (1/3-octave-bands from 10 Hz to 63.1 kHz). Cumulative distribution functions were used to evaluate SRKW's noise exposure from 15 vessel categories over three zones located within the KDE. Median cumulative noise values were used to group categories based on the associated exposure levels. Ferries, Tugboats, Vehicle Carriers, Recreational Vessels, Containers, and Bulkers showed high levels of exposure (Leq−50th > 90 dB re 1 μPa) within SRKW core areas. Management actions aiming at reducing SRKW noise exposure during the summer should target the abovementioned categories and take into consideration the spatial distribution of their levels of exposure, their mechanical and their operational characteristics.
Bringing western science and policy together with Traditional Knowledge and values from indigenous communities for ocean planning is lacking and a framework is needed. This article articulates indigenous perspectives about the ocean and a culturally appropriate methodology developed in the Bering Strait region for a visioning process that can be used to bridge western and indigenous value systems. Recommendations for an indigenous approach focused on inclusion, the examination of values, adequate representation, and Tribal direction in ocean planning and policy are made. This approach is needed to move forward on a path to achieving more equitable, sustainable and inclusive ocean planning for the future.
Fishers are often perceived to be poor, and low income levels are used to justify subsidies and other types of direct and indirect income support to maintain coastal communities. In this study fishers’ income levels are investigated in four Nordic countries; Denmark, Iceland, Norway and Sweden for different types of fishers and vessels and in comparison to alternative occupations. The most important result is that fishers in these countries are doing relatively well, and only in Sweden is the fishers’ average income level below the average national income. Within the fleets, there are substantial differences. Owners of coastal vessels tend to have the lowest income, and also lower than crews. Owners as well as crews on larger vessels tend to do much better and in the largest fishing nations, Iceland and Norway, they do especially well.
Systematic conservation planning (SCP) has increasingly been used to prioritize conservation actions, including the design of new protected areas to achieve conservation objectives. Over the last 10 years, the number of marine SCP studies has increased exponentially, yet there is no structured or reliable way to find information on methods, trends, and progress. The rapid growth in methods and marine applications warrants an updated analysis of the literature, as well as reflection on the need for continuous and systematic documentation of SCP exercises in general. To address these gaps, we developed a database to document SCP exercises and populated it with 155 marine SCP exercises found in the primary literature. Based on our review, we provide an update on global advances and trends in marine SCP literature. We found accelerating growth in the number of studies over the past decade, with increasing consideration of socioeconomic variables, land-sea planning, and ecological connectivity. While several studies aimed to inform conservation decisions, we found little evidence of input from practitioners. There are important gaps in geographic coverage and little correspondence with areas most threatened. Five countries lead most studies, but their networks suggest potential for capacity building through collaborations. The varying quality and detail in documentation of studies confirmed the limited opportunities to develop and assess the application of best practice in conservation planning. A global database to track the development, implementation, and impact of SCP applications can thus provide numerous benefits. Our database constitutes an important step towards the development of a centralized repository of information on planning exercises and can serve several roles to advance SCP theory and practice: it facilitates assessing geographic coverage and gaps; scientists and practitioners can access information to identify trends in the use of data, methods, and tools; reviewers and editors of journals can assess whether studies have covered important literature and developments; donors and non-government organizations can identify regions needing further work; and practitioners and policy-makers can learn from previous plans.
Ocean acidification typically reduces calcification in tropical marine corals but the mechanism for this process is not understood. We use skeletal boron geochemistry (B/Ca and δ11B) to reconstruct the calcification fluid DIC of corals cultured over both high and low seawater pCO2 (180, 400 and 750 μatm). We observe strong positive correlations between calcification fluid pH and concentrations of the DIC species potentially implicated in aragonite precipitation (be they CO32−, HCO3− or HCO3− + CO32−). Similarly, with the exception of one outlier, the fluid concentrations of precipitating DIC species are strongly positively correlated with coral calcification rate. Corals cultured at high seawater pCO2usually have low calcification fluid pH and low concentrations of precipitating DIC, suggesting that a reduction in DIC substrate at the calcification site is responsible for decreased calcification. The outlier coral maintained high pHCF and DICCF at high seawater pCO2 but exhibited a reduced calcification rate indicating that the coral has a limited energy budget to support proton extrusion from the calcification fluid and meet other calcification demands. We find no evidence that increasing seawater pCO2 enhances diffusion of CO2into the calcification site. Instead the overlying [CO2] available to diffuse into the calcification site appears broadly comparable between seawater pCO2 treatments, implying that metabolic activity (respiration and photosynthesis) generates a similar [CO2] in the vicinity of the calcification site regardless of seawater pCO2.
Identifying and counting fish individuals on photos and videos is a crucial task to cost-effectively monitor marine biodiversity, yet it remains difficult and time-consuming. In this paper, we present a method to assist the identification of fish species on underwater images, and we compare our model performances to human ability in terms of speed and accuracy. We first tested the performance of a convolutional neural network (CNN) trained with different photographic databases while accounting for different post-processing decision rules to identify 20 fish species. Finally, we compared the performance of species identification of our best CNN model with that of humans on a test database of 1197 fish images representing nine species. The best CNN was the one trained with 900,000 images including (i) whole fish bodies, (ii) partial fish bodies and (iii) the environment (e.g. reef bottom or water). The rate of correct identification was 94.9%, greater than the rate of correct identification by humans (89.3%). The CNN was also able to identify fish individuals partially hidden behind corals or behind other fish and was more effective than humans to identify fish on smallest or blurry images while humans were better to identify fish individuals in unusual positions (e.g. twisted body). On average, each identification by our best CNN using a common hardware took 0.06 s. Deep Learning methods can thus perform efficient fish identification on underwater images and offer promises to build-up new video-based protocols for monitoring fish biodiversity cheaply and effectively.
During traditional boat-based surveys of marine megafauna, behavioral observations are typically limited to records of animal surfacings obtained from a horizontal perspective. Achieving an aerial perspective has been restricted to brief helicopter or airplane based observations that are costly, noisy, and risky. The emergence of commercial small unmanned aerial systems (UAS) has significantly reduced these constraints to provide a stable, relatively quiet, and inexpensive platform that enables replicate observations for prolonged periods with minimal disturbance. The potential of UAS for behavioral observation appears immense, yet quantitative proof of utility as an observational tool is required. We use UAS footage of gray whales foraging in the coastal waters of Oregon, United States to develop video behavior analysis methods, determine the change in observation time enabled by UAS, and describe unique behaviors observed via UAS. Boat-based behavioral observations from 53 gray whale sightings between May and October 2016 were compared to behavioral data extracted from video analysis of UAS flights during those sightings. We used a DJI Phantom 3 Pro or 4 Advanced, recorded video from an altitude ≥25 m, and detected no behavioral response by whales to the UAS. Two experienced whale ethologists conducted UAS video behavioral analysis, including tabulation of whale behavior states and events, and whale surface time and whale visible time (total time the whale was visible including underwater). UAS provided three times more observational capacity than boat-based observations alone (300 vs. 103 min). When observation time is accounted for, UAS data provided more and longer observations of all primary behavior states (travel, forage, social, and rest) relative to boat-based data, especially foraging. Furthermore, UAS enable documentation of multiple novel gray whale foraging tactics (e.g., headstands: n = 58; side-swimming: n = 17; jaw snapping and flexing: n = 10) and 33 social events (nursing and pair coordinated surfacings) not identified from boat-based observation. This study demonstrates the significant added value of UAS to marine megafauna behavior and ecological studies. With technological advances, robust study designs, and effective analytical tools, we foresee increased UAS applications to marine megafauna studies to elucidate foraging strategies, habitat associations, social patterns, and response to human disturbance.
Cape monkfish (Lophius vomerinus) is one of the long-lived species and top predators in the northern Benguela region. Studies on bioaccumulation of mercury (Hg) in cape monkfish are limited. This study compared the total Hg concentration between monkfish muscle and liver tissue; and related the monkfish total Hg concentrations to fish body size and capture locations (depth and latitude). Monkfish specimens (n = 529) were collected from 2016 to 2018. The mean total Hg concentration was 0.126 ± 0.005 mg/kg in muscle tissues and 0.106 ± 0.005 mg/kg in liver tissues. No significant differences were observed between total Hg concentrations of muscles and liver tissues. Differences in Hg concentrations between monkfish length classes were observed. No significant correlation was found between total Hg concentrations and latitude. A significant increase of total Hg concentration with the depth was observed. The concentrations of Hg were below the World Health Organization (WHO limits for fish (0.5 mg/kg).
Species distribution models (SDMs) are statistical tools aiming at mapping and predicting species distributions across landscapes. Data acquisition being limited in space and time, SDM are commonly used to predict species distribution in unsampled areas or years, with the expectation that modelled habitat–species relationships will hold across spatial or temporal contexts (i.e., model transferability). This key aspect of habitat modelling has major implications for spatial management, yet it has received limited attention, especially in the dynamic marine realm. Our aims were to test geographical and temporal habitat model transferability and to make recommendations for future population‐scale habitat modelling.
Two contrasted regions of the North Western Mediterranean Sea: the cold and productive waters of the Gulf of Lion, and the warm and oligotrophic waters of Corsica.
We GPS‐tracked 189 Scopoli's shearwaters, Calonectris diomedea, at four breeding sites during the chick‐rearing period in 2011 and 2012 (418 foraging trips), and analysed their fine‐scale foraging behaviour. We then built colony‐specific habitat models (GAMMs) to test SDM geographical and temporal transferability and investigated the effect of extrinsic (environmental extrapolation) and intrinsic (trip characteristics) factors on transferability.
Scopoli's shearwaters from our four study sites had comparable foraging strategies (as assessed from trip characteristics and isotopic diet tracers). Despite such similarities, SDMs revealed colony‐specific habitat associations. Geographical and temporal model transferability was better within than between regions.
Crucially, our study illustrates how habitat–species relationships can vary between colonies located <200 km apart, and underlines the effect of spatio‐temporal extrapolation in habitat modelling. We therefore warn that defining adequate spatial scales for model predictions is critical to sound marine spatial planning and conservation.
Coral reef degradation due to environmental change, including anthropogenic disturbances, is a major concern worldwide. Detecting and assessing both temporal and spatial changes in benthic cover is a crucial requirement to inform policy makers and guide conservation measures. Here, we introduce a spatial approach based on high resolution multispectral and hyperspectral image analysis, developed in order to detect and quantify changes in benthic cover in a highly heterogeneous shallow coral reef flat in Reunion Island in the South-West Indian Ocean. We propose a new index called HCAI (Hyperspectral Coral to Algae Index), defined as the ratio of living coral cover to the sum of living coral and algal covers. Benthic cover estimates were derived from airborne hyperspectral image processing using water column correction and unmixing models implemented with the four main coral reef benthic components: corals, algae, seagrass and sand. Ground truth and LIDAR data acquired simultaneously were used to validate processing accuracy. A significant positive correlation (adjusted R2 = 0.72, p-value < 0.001) was obtained between coral cover recorded in situ and estimated from image analysis. Moreover, 13 habitat classes based on the four main benthic component covers were mapped at a scale of an entire reef. Diachronic analyses of hyperspectral images between 2009 and 2015 revealed an overall decrease of the HCAI index and a decrease in the area of all the dominant coral classes along the reef (−28.24% for the coral class for example), while the area of habitat classes dominated by algae strongly increased during the same period. Moreover, we detected and documented the spatial and temporal evolutions of coral geomorphological features composed with coral rubble deposits called rubble tongues (RTs) using different available sensors (i.e. hyperspectral, satellite, and orthophotography). Since 2003, four detected (RTs) have spread shoreward at a mean rate of 8.4 m.y−1 including significant loss of reef structural complexity and heterogeneity, a spreading pattern which was confirmed by 2009 and 2015 hyperspectral data. Remote sensing and more specifically airborne hyperspectral approaches open new perspectives for coral reef monitoring, at high temporal and spatial resolutions.
Vessel traffic has been increasing rapidly in the Arctic, and within the Canadian Arctic, tourist vessels are the fastest growing maritime sector. Vessel traffic can cause a variety of impacts on whales, including ship strikes and acoustic disturbance. Here, the overlap between tourist vessels (e.g., pleasure craft/yachts and passenger vessels/cruise ships) and whale concentration areas is assessed within the Inuvialuit Settlement Region of the western Canadian Arctic. Different management measures which could be used to reduce impacts on whales are also assessed. Passenger vessels have had a relatively constant overlap with whale concentration areas through time, whereas pleasure craft have had a recent and rapid increase. Passenger vessels may have a greater impact on whales, compared to pleasure craft, since they are larger and travel faster. Excluding vessels from the two marine protected areas in the region would have no impact on whales within concentration areas, since vessels would likely just be displaced to adjacent areas with similar whale concentrations. Restricting vessels to the Canadian government's proposed low-impact corridor may reduce impact slightly, but creating a corridor completely outside of the known whale area could more significantly reduce the potential impact of vessels on whales in those areas. Restricting vessel speed within whale areas would also reduce the impact of passenger vessels, but would not likely reduce the impact of pleasure craft. Overall, a combination of management measures may be the best way to reduce impacts on whales in concentration areas.
Slow growing, massive stony corals have often been overlooked in reef-restoration activities, despite their resilience to climate change and contribution to reef framework. Techniques to effectively propagate and outplant these species have proven challenging. However, advancement in methodology may increase rates of success. In 2013, Orbicella faveolataand Montastrea cavernosa fragments were outplanted on reefs in the Florida Keys at a nearshore and offshore location, to determine whether “microfragmenting” corals, the process of creating ∼1 cm2 fragments, increased outplant survival and growth compared with larger fragments (16–64 cm2).
Arrays of eight microfragments were planted near one larger fragment of similar size at each location. Six replicate pairs were haphazardly placed within each ∼700 m2 study site. Fragments at both sites were monitored for growth and survival over 31 months, spanning two bleaching events. Initial predation occurred on microfragments, but was absent in the larger fragments. Survival and growth differed between sites, but did not differ between the larger fragments and microfragment arrays. However, excluding plots with >40% predation at the nearshore site showed that O. faveolata microfragment arrays produced 10 times more tissue than traditionally used larger fragments. Results from this study suggest that if predation events are reduced, massive corals can be successfully grown and outplanted for restoration purposes.