Accurate ocean forecasts require sufficient observations to resolve key processes, yet conventional observing systems often miss fine-scale variability in dynamic ocean regions. Top predators frequently target these features, offering an opportunity for instrumented animals to sample underrepresented areas. Here, we use sharks equipped with depth- and temperature-sensing satellite tags as opportunistic ocean observers to reduce climate forecast errors in a proof-of-concept model experiment. We compiled >8200 high-resolution shark-derived depth-temperature profiles from the Northwest Atlantic Ocean and used these data to inform an operational forecasting model. Retrospective forecasts incorporating shark-derived observations showed up to 40% lower surface temperature error than control forecasts when compared against reference satellite observations and ocean reanalysis products. Forecast improvements from shark-derived measurements were strongest in dynamic shelf and slope regions that traditional observing approaches often under-sample. These results demonstrate the potential for animal-borne observations to strengthen operational forecasting and capture complex, ecologically important dynamics in a changing ocean.

Pelagic Seascape classifications delineate spatially explicit water masses based on distinctive biogeochemical features. These are expected to act as dynamic habitats for marine megafauna that influence their movement. Here, we test if marine megafauna respond to a free, globally consistent, publicly available pelagic Seascape data-product in ways that are consistent with habitat selection of land animals using taxa with contrasting ecologies. We compiled a large satellite-tracking dataset (n = 82 individuals) comprising blue sharks (Prionace glauca, n = 28), leatherback turtles (Dermochelys coriacea, n = 26), and fin whales (Balaenoptera physalus, n = 28), tagged between 2014 and 2025. We then compared their movements across the Northwest Atlantic Ocean to Seascapes to develop dynamic resource selection functions (RSFs). Our results confirm that pelagic Seascapes act as ecologically meaningful categorical proxies of dynamic habitats and provide evidence that broad-scale movement decisions of marine fauna are structured by interacting and co-occurring biophysical features. We also reveal how pelagic Seascapes could be used in an applied context, serving as near-real time indicators of areas where marine megafauna are more likely to occur. This work demonstrates that three ecologically distinct species of marine megafauna select pelagic seascapes, analogous to habitat selection observed in terrestrial systems. We highlight the value of Seascapes as a simple, intuitive, and transferable framework for movement ecology, and anticipate that their application will foster new opportunities to apply concepts from landscape ecology into the pelagic marine realm.

Biologging studies of sharks have traditionally relied on animal capture and restraint to deploy fin-mounted satellite-linked transmitters, approaches that may induce stress, behavioral alterations, and post-release mortality. Here we evaluate a method for remotely deploying dorsal fin-mounted satellite transmitters on free-swimming sharks without capture and handling. This technique employed a modified Low Impact Minimally Percutaneous Electronic Transmitter (LIMPET) tagging system, originally developed for cetaceans, to deliver modified Smart Positioning and Temperature (SPOT) transmitting tags to the dorsal fins of free-swimming white sharks (Carcharodon carcharias). We detail the tagging system configuration, including transmitter modifications, deployment hardware, calibration procedures, and field protocols designed to maximize accuracy and attachment success. Field deployments on six sharks resulted in tag deployment with no observable behavioral signs of stress. Tag performance was influenced by placement location on the fin and dart penetration, with deployments near the dorsal fin apex and leading edge improving retention and transmission efficiency. We discuss the strengths and limitations of this approach, the types of species and study applications it’s best suited for and provide recommendations to improve transmitter design and deployment techniques for sharks. This method offers a less-invasive alternative to conventional fin-mounted shark tagging techniques requiring capture and applicable for shorter-term movement studies of large, surface-oriented species where capture and restraint are impractical or may compromise animal welfare or study objectives.

ABSTRACT Shark populations are declining globally and the effectiveness of marine protected areas (MPAs) as a conservation tool may vary by species and environmental context. This study assessed space use and residency of smoothhound sharks ( Mustelus mustelus )—an endangered, yet highly exploited shark—in relation to spatial protection and fishing risk across three areas off the southern coast of South Africa. Passive acoustic telemetry data (2016–2023) from 37 individual sharks were analysed using residency indices and generalised additive models. Smoothhounds exhibited high site fidelity, with small daily home ranges (< 10 km 2 ). Residency showed a weak but significant negative relationship with fishing risk, indicating reduced residency in areas of higher fishing pressure. Residency was consistently higher within a MPA and adjacent bay waters, as compared to a nearby unprotected bay. These findings suggest that smoothhounds may respond to spatial protection and suggest that extending protection to the MPA‐adjacent high‐use areas could enhance conservation outcomes.

The movement behavior of open ocean fishes is challenged by metabolic demands resulting from sustained swimming and the availability of resources in a dynamic, ephemeral environment. Advances in electronic tagging and tracking technologies have permitted unprecedented opportunities to describe the movements of open ocean fishes in these environments, however, our understanding of the mechanistic drivers of individual variation in movement performance is limited. In this study, we tested the hypothesis that movement capacities of open ocean sharks would be related to physiology and body condition. We measured the physiological status (e.g., energy stores and body condition) of blue sharks (Prionace glauca) captured in the open ocean, and then tracked their movements over 45 days. We then explored for relationships between physiological metrics and individual differences in metrics of movement behavior (distance traveled, activity space, behavioral state, and tortuosity) of the tracked blue sharks. Analyses detected consistent positive relationships between individual plasma triglyceride concentrations and body condition (sampled at time of capture) on distance traveled, activity space, behavioral state, and tortuosity - up to 45 days post tagging, with models explaining up to 79% of individual variation in movement. These findings highlight the potential role of metabolic lipid reserves in shaping movement behavior of open ocean, predatory sharks in patchy, ephemeral environments. More broadly, they offer new insight into the factors which may influence individual variation in the timing and scale of movement in oceanic fishes.

Understanding how marine populations adapt to their environment is important for effective management. Range shifts can decrease genetic diversity, reducing species' ability to resist extinction. The bull shark Carcharhinus leucas is a large coastal predator that uses shallow water habitats as nurseries, the extent of which defines the adult range. In the northwest Atlantic, the historic northernmost nursery for bull sharks was in the Indian River Lagoon (IRL), Florida (USA). Recently, bull sharks were shown to have founded a new nursery in Pamlico Sound (PS), North Carolina, due to warming water. To describe the evolutionary patterns associated with this change, we investigated genetic connectivity and diversity using 15 microsatellite loci among juvenile bull sharks from both the historic and contemporary IRL, the novel PS nursery, and sites in southern Florida and the Gulf of Mexico. We identified connectivity between the historic IRL and PS populations, indicating an IRL origin for the new nursery. We also found significant structure between the historic and contemporary IRL populations, but not between the contemporary IRL and southern Florida, supporting a population-wide poleward shift. These results show that northwestern Atlantic bull sharks are altering their life history to cope with warming water, and demonstrate for the first time that a large coastal predator is undergoing a genetic response to climate change.

Artificial light at night (ALAN) is a pervasive pollutant which can extend into coastal waters. Previous studies have revealed that ALAN can suppress melatonin levels in teleost fishes. However, the effects of ALAN on elasmobranch physiology have yet to be investigated. To address this knowledge gap, we examined the relationship between ALAN exposure and blood melatonin levels in wild nurse (Ginglymostoma cirratum) and blacktip (Carcharhinus limbatus) sharks sampled off Miami, Florida (USA). We hypothesized that sharks sampled at night in metropolitan areas exposed to high ALAN, would exhibit lower blood melatonin concentrations, compared to conspecifics sampled in adjacent more pristine areas with low ALAN. As shark level of mobility would likely influence exposure to ALAN, we further hypothesized species-specific differences in our results as nurse sharks are relatively sedentary, whereas blacktips are highly mobile. We also tested for the potential influence of other biological and environmental factors, along with exposure to ALAN, on species-specific melatonin levels. Consistent with our hypothesis, nurse sharks exposed to higher ALAN exhibited significantly lower melatonin concentrations compared to individuals sampled in areas with lower ALAN. Melatonin concentrations measured in blacktips did not differ between individuals sampled in high versus low areas of ALAN. These results suggest that exposure to ALAN can suppress melatonin levels in wild sharks, and that these effects may be influenced by species-specific mobility; specifically, species that are highly resident to areas of high ALAN may be more prone to this anthropogenic pollutant compared to highly mobile species that readily move between areas of high and low ALAN. The melatonin levels found here for nurse (24.6 to 425.2 pg/mL) and blacktip sharks (27.4 to 628.7 pg/mL) also represent the first assessment of blood melatonin levels reported in sharks, providing baseline information for future monitoring and inter- and intra-species comparisons.

Vessel strikes are the leading cause of sea turtle strandings. However, there is limited information on how the presence of vessel traffic can impact sea turtle behavior and space use. Currently, research into these responses consists primarily of lab studies, as in situ studies pose logistical challenges. In this study, we present a method to understand these responses in the field using both acoustic telemetry and passive acoustic monitoring to quantify turtle movement and vessel traffic, respectively. Between 2019 and 2022, we tracked green (Chelonia mydas, n = 7) and loggerhead (Caretta caretta, n = 6) turtles within Biscayne National Park (Florida, United States). We used two miniature acoustic telemetry arrays (5 receivers each), with a central passive acoustic recorder in each array to quantify vessel traffic. In addition to recording turtle presence, data from transmitters containing tri-axial accelerometers allowed us to quantify turtle activity. We used generalized linear models to determine the relationship of turtle residency and activity to hourly and daily vessel traffic. Our results indicated a weak but significant negative relationship between turtle residency and vessel traffic. We also observed reduced activity levels in response to increased vessel presence. This study demonstrates a viable in situ method for quantifying the sub-lethal impacts of vessel traffic to sea turtles, revealing that even vessel presence alone can alter sea turtle behavior. These findings provide critical information for managing vessel activity in protected areas to mitigate behavioral disturbances, not just direct mortality.

Animal movement data have transformed our understanding of ecological systems and shaped conservation practice, but have limited influence on tracking progress towards international biodiversity goals. Existing biodiversity indicators adopted in frameworks such as the Kunming–Montréal Global Biodiversity Framework — the primary multilateral conservation agreement that aims to halt and reverse biodiversity loss by 2030 — are typically not responsive enough to detect biodiversity change in time to guide action, nor sufficiently biologically informative to explain or predict changes. In this Perspective, we provide seven reasons why movement data can help to tackle these limitations by adding biological realism, mechanistic understanding, and early-warning capacity to current and future indicators. Movement data already inform conservation efforts, from local management to global treaties for migratory species, and are increasingly helpful to uncover sources of environmental change, while enhancing monitoring capability and policy relevance. We recommend that the scientific community ground existing connectivity metrics in empirical movement data, develop new indicators that flag rapid change, and invest in modelling and attribution studies that use movement data to identify drivers of biodiversity loss and recovery. Biodiversity indicators are essential for tracking progress towards international biodiversity goals, but existing indicators have important shortcomings and are not based on animal movement data. This Perspective outlines why incorporating movement data into biodiversity indicators can help to address these shortcomings, improve monitoring and inform effective conservation actions.

South Africa was the first country to protect white sharks Carcharodon carcharias—an important decision taken despite limited data on population status, but guided by a precautionary approach in recognition of the species’ ecological and economic value. Unfortunately, several lines of evidence suggest an ongoing population reduction, including declines in sightings from aggregation sites in the last decade (especially of large mature individuals), low genetic diversity, and low effective population size. Simulation modelling indicated that current levels of white shark removals by South Africa’s lethal shark control program are alone unsustainable and sufficient to drive population decline. This has led to growing calls for further conservation actions. Nevertheless, a recent study has claimed that this population has remained stable since 1991 and likely redistributed eastward due to the predatory effects of orcas. On this basis, no additional conservation management action has yet been taken. Here, we synthesize several lines of historical and newly acquired information to argue that this white shark population is more likely in decline. While predator-prey dynamics are natural phenomena, anthropogenic threats (i.e. the lethal shark control program and demersal shark fishery) are subject to management. We recognize that management must balance public safety, community livelihoods, and conservation goals. However, consistent with the country’s history of applying a precautionary approach and its commitments to existing national and international frameworks, we urge the South African government to reduce anthropogenic sources of white shark mortality, to conserve this population and its attendant ecosystem services that South Africans depend upon.

Satellite telemetry has enabled the tracking of marine predators’ vertical and horizontal habitat use and migration patterns. These insights provide valuable information that inform management and conservation of threatened species. In this study, a scalloped hammerhead, Sphyrna lewini, (125 cm FL; immature female) a Carolina hammerhead, Sphyrna gilberti, (138 cm FL; immature female) and a scalloped/Carolina hammerhead hybrid (160 cm FL; immature male) were tagged with PSATLIFE’s off the coast of North Carolina. Tag data revealed that the Carolina hammerhead exploited a wide depth range, with a maximum depth of 846 m. Dive patterns of the scalloped hammerhead revealed differences in vertical space use, with the scalloped hammerhead primarily remaining within the top 200 m of the water column, and with a maximum depth of 380 m. The hybrid individual demonstrated similar dive patterns to those of the scalloped hammerhead, with a maximum depth of 203 m. This study presents the first vertical movement data for Carolina and hybrid scalloped/Carolina hammerheads, offering new insights into interspecific variation in depth use. Future research should explore if there are differences in habitat use and foraging strategies, as they may serve as distinguishing characteristics and support the development of effective management measures.

We investigated the relationship between blood metal(loid) concentrations and plasma levels of glucose, proteins, triglycerides, cholesterol, lactate, urea, and polyunsaturated fatty acids in tiger sharks (Galeocerdo cuvier) sampled off the Fernando de Noronha Archipelago, a remote oceanic marine protected area in the Equatorial Atlantic Ocean. Results revealed that Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn were detected in the whole blood of tiger sharks and no sexual differences in blood metal(loid) concentrations were observed. Females had higher concentrations of plasma proteins and docosahexaenoic acid. In females, all analyzed elements were positively correlated with each other, except As. Only As was positively correlated with triglycerides, suggesting a potential impact of As exposure on the nutritional condition of this species. The results presented herein reinforce that sharks, even from remote sites, are exposed to metal(loid)s and that such exposure might elicit physiological responses.

Graphical AbstractThis study provides empirical evidence of a trophic cascade following the loss of white sharks (Carcharodon carcharias) from False Bay, South Africa. Arrow thickness represents the relative strength of top-down predation effects (thicker arrows indicate stronger effects, thinner arrows indicate weaker effects). Left Panel: Historically, white sharks occupied the apex of the food web, preying on Cape fur seals (Arctocephalus pusillus pusillus) and both competing with and feeding on sevengill sharks (Notorynchus cepedianus). Seals primarily preyed on schooling fishes, while sevengill sharks primarily preyed on benthic sharks. Right Panel: Following the decline and eventual disappearance of white sharks from False Bay, both seals and sevengill sharks have increased in relative abundance, coinciding with declines in small fish that seals feed on and smaller sharks that sevengills prey upon. Illustration by Kelly Quinn / Canvas of the Wild.

For highly mobile marine species such as pelagic elasmobranchs, the development of effective spatial management requires a comprehensive understanding of movement ecology. Research incorporating movement data across seasons and life stages, including reproductive states, is valuable for informing spatial management, yet is absent for most species. In the Northwest (NW) Atlantic Ocean (hereafter referred to as NW Atlantic), the porbeagle shark Lamna nasus is a pelagic species that is overfished, has a live retention ban (Canada) or landings regulations (United States), and is also commonly captured incidentally as bycatch. Research on the spatiotemporal dynamics of NW Atlantic porbeagle habitat use is limited, with all previous research utilizing pop-off satellite archival tags that are prone to large uncertainty in location estimates. This study used higher-accuracy fin-mount satellite tags to identify patterns in habitat use across life stages and seasons for porbeagle sharks tagged off the northeastern coast of the United States. During the summer and fall, the 95% kernel density estimate (referred to as “activity space”) of tagged porbeagles occurred almost exclusively on the continental shelf in the Gulf of Maine and Georges Bank. Activity space expanded and shifted southwards to include offshore environments during the winter and spring for juveniles, mature non-gravid females, and mature females of unknown reproductive states, while the activity space of mature males and gravid females remained in shelf waters year-round. This finding differs from the previous assumption that southward migrations are linked to reproduction for NW Atlantic porbeagles. Tagged porbeagles were also found to have a relatively small 50% kernel density estimate (referred to as “high occupancy area”) located around Cape Cod, Massachusetts that was well-conserved across life stages and seasons. This relatively static, small high occupancy area has implications for the population’s conservation given the high amount of fishing activity (rod-and-reel, trawl, gillnet) occurring within this region. Given the overlap between porbeagle high occupancy area and fishing activity, as well as the relatively high recapture rate of tagged sharks (10.5%), the coastal waters around Cape Cod, Massachusetts should be considered for spatial management of the NW Atlantic porbeagle.

Bowlby et al. (2023) assessed spatio-temporal trends in South Africa’s white shark (Carcharodon carcharias) population using a range of different proxies of white shark occurrence. The authors concluded that, despite significant declines in white shark sightings in several historical aggregation sites, the population as a whole has remained relatively stable throughout South Africa since its protection in 1991. The study also suggests a population redistribution eastward, likely driven by natural predator–prey dynamics (i.e., predation and related risk from orcas, Orcinus orca). Here, we highlight several issues with the methods and the inferences made in that study and argue that the data, as currently analysed and interpreted, cannot support population stability, or redistribution, of South Africa’s white sharks. We also point out that the onset of the decline of white sharks at historical aggregation sites began before the documented appearance of specialist shark-eating orcas (the main alleged cause of the decline put forward in Bowlby et al. 2023). Our concern is that unsupported claims of population stability could jeopardize conservation actions urgently needed for white sharks, if the declines documented at their historical aggregations are representative of the population trend. Below we summarize our arguments.

An important provision of the Minamata Convention on Mercury is to monitor and evaluate the effectiveness of the adopted measures and its implementation. Here, we describe for the first time currently available biotic mercury (Hg) data on a global scale to improve the understanding of global efforts to reduce the impact of Hg pollution on people and the environment. Data from the peer-reviewed literature were compiled in the Global Biotic Mercury Synthesis (GBMS) database (>550,000 data points). These data provide a foundation for establishing a biomonitoring framework needed to track Hg concentrations in biota globally. We describe Hg exposure in the taxa identified by the Minamata Convention: fish, sea turtles, birds, and marine mammals. Based on the GBMS database, Hg concentrations are presented at relevant geographic scales for continents and oceanic basins. We identify some effective regional templates for monitoring methylmercury (MeHg) availability in the environment, but overall illustrate that there is a general lack of regional biomonitoring initiatives around the world, especially in Africa, Australia, Indo-Pacific, Middle East, and South Atlantic and Pacific Oceans. Temporal trend data for Hg in biota are generally limited. Ecologically sensitive sites (where biota have above average MeHg tissue concentrations) have been identified throughout the world. Efforts to model and quantify ecosystem sensitivity locally, regionally, and globally could help establish effective and efficient biomonitoring programs. We present a framework for a global Hg biomonitoring network that includes a three-step continental and oceanic approach to integrate existing biomonitoring efforts and prioritize filling regional data gaps linked with key Hg sources. We describe a standardized approach that builds on an evidence-based evaluation to assess the Minamata Convention’s progress to reduce the impact of global Hg pollution on people and the environment.

Animal migration has fascinated scientists and the public alike for centuries, yet migratory animals are facing diverse threats that could lead to their demise. The Anthropocene is characterised by the reality that humans are the dominant force on Earth, having manifold negative effects on biodiversity and ecosystem function. Considerable research focus has been given to assessing anthropogenic impacts on the numerical abundance of species/populations, whereas relatively less attention has been devoted to animal migration. However, there are clear linkages, for example, where human-driven impacts on migration behaviour can lead to population/species declines or even extinction. Here, we explore anthropogenic threats to migratory animals (in all domains - aquatic, terrestrial, and aerial) using International Union for the Conservation of Nature (IUCN) Threat Taxonomy classifications. We reveal the diverse threats (e.g. human development, disease, invasive species, climate change, exploitation, pollution) that impact migratory wildlife in varied ways spanning taxa, life stages and type of impact (e.g. from direct mortality to changes in behaviour, health, and physiology). Notably, these threats often interact in complex and unpredictable ways to the detriment of wildlife, further complicating management. Fortunately, we are beginning to identify strategies for conserving and managing migratory animals in the Anthropocene. We provide a set of strategies that, if embraced, have the potential to ensure that migratory animals, and the important ecological functions sustained by migration, persist.

Distribution of species across jurisdictional and physical boundaries poses a challenge to management and research, and these transboundary species tend to suffer more-severe population declines from fisheries exploitation. Large pelagic sharks like the porbeagle shark, Lamna nasus, are particularly vulnerable to anthropogenic pressures due to their life history characteristics and their highly migratory behaviour. However, limited knowledge of their precise spatio-temporal movements is particularly challenging for management in situations where jurisdictional boundaries change over small spatial scales. We used satellite tags to demonstrate that porbeagle sharks tagged in the northern Northeast (NE) Atlantic (n = 3), display inter-individual variation in behaviour. Tagged sharks undertook rapid horizontal movements (up to 100 km per day) while transiting through multiple physical habitats and management jurisdictions in a matter of days along different paths. The spatial scale of these movements is important now that the population is deemed in recovery and a new catch advice for porbeagle sharks has been issued by ICES for the first time since 2009 in the NE Atlantic. These movement data highlight the value of existing, and need for continued, regional collaboration to inform sustainable fisheries and conservation management. This is achieved by maximising research impact through cross border funding mechanisms to fill knowledge gaps of species' life-history and ecology, and, in turn, improve respective outcomes for vulnerable and highly mobile shark species.