Figure - available from: Nature
This content is subject to copyright. Terms and conditions apply.
Effect of grid-cell size on risk-exposure patterns of sharks to longline fisheries
a–d, North Atlantic Ocean (a), east Pacific Ocean (b), southwest Indian Ocean (c) and Oceania (d). Note that, regardless of the grid-cell size at which the individual-species mean spatial overlap and FEI were calculated, the species that occur in the highest-(red) and the lowest-risk zones (green) remain notably conserved, which indicates a general pattern that is not dependent on the scale at which these data were analysed. Shark-species identification codes corresponding to marker colours are given in Fig. 3. In addition, for the North Atlantic (a), hammerhead sharks (Sphyrna spp.) are represented by a black circle and oceanic whitetip sharks (C. longimanus) by a light blue circle; for the eastern Pacific Ocean (b), the salmon shark (L. ditropis) is represented by a light orange circle. Error bars are ± 1 s.d. An additional comparison of 2° × 2° with 1° × 1° grid-cell size is given in Supplementary Fig. 4.

Effect of grid-cell size on risk-exposure patterns of sharks to longline fisheries a–d, North Atlantic Ocean (a), east Pacific Ocean (b), southwest Indian Ocean (c) and Oceania (d). Note that, regardless of the grid-cell size at which the individual-species mean spatial overlap and FEI were calculated, the species that occur in the highest-(red) and the lowest-risk zones (green) remain notably conserved, which indicates a general pattern that is not dependent on the scale at which these data were analysed. Shark-species identification codes corresponding to marker colours are given in Fig. 3. In addition, for the North Atlantic (a), hammerhead sharks (Sphyrna spp.) are represented by a black circle and oceanic whitetip sharks (C. longimanus) by a light blue circle; for the eastern Pacific Ocean (b), the salmon shark (L. ditropis) is represented by a light orange circle. Error bars are ± 1 s.d. An additional comparison of 2° × 2° with 1° × 1° grid-cell size is given in Supplementary Fig. 4.

Source publication
Article
Full-text available
Effective ocean management and conservation of highly migratory species depends on resolving overlap between animal movements and distributions and fishing effort. Yet, this information is lacking at a global scale. Here we show, using a big-data approach combining satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of...

Similar publications

Article
Full-text available
Known as input in the Numerical Weather Prediction (NWP) models, Microwave Radiation Imager (MWRI) data have been widely distributed to the user community. With the development of remote sensing technology, improving the geolocation accuracy of MWRI data are required and the first step is to estimate the geolocation error accurately. However, the t...
Article
Full-text available
In organizations, companies or agencies such as the Office of Communication and Information Technology, presence has become one of the critical things in assessing the performance of workers/employees. There are several ways to do attendance, where one of them can facilitate the present process with digital tools/machines such as smartphones that u...
Article
Full-text available
For migratory animals, events at one stage of the annual cycle can produce constraints or benefits that carry over to subsequent stages. Differing life-history strategies among individuals can influence the expression of these carry-over effects, leading to pronounced within-population variation in migration. For example, reproductive roles can dri...
Conference Paper
Full-text available
This paper presents the on-going work of MyDNAmark crowdsourcing biodiversity mobile application which enable the researchers and public alike to collaboratively record the species information and observation. The MyDNAmark application utilizes the Cordova API and various other APIs such as RESTful and Google Map to provide a means to display the c...
Article
Full-text available
Educational attainment is an important social determinant of maternal, newborn, and child health1–3. As a tool for promoting gender equity, it has gained increasing traction in popular media, international aid strategies, and global agenda-setting4–6. The global health agenda is increasingly focused on evidence of precision public health, which ill...

Citations

... Combined assessments of this information with data from EO missions enables researchers to investigate the environmental factors and mechanisms that drive the observed movement patterns. As a result, researchers have identified biotic and abiotic EOVs such as SST, dissolved oxygen (DO), SSS, ocean color (a proxy for primary productivity), mesoscale eddies, and oceanographic fronts that influence the 3-dimensional distribution of pelagic elasmobranchs [11][12][13]. However, environmental data from EO missions still lack the required spatial resolution for ground-site or organismlevel analyses. ...
Full-text available
Preprint
AEROS is a 3U CubeSat pathfinder toward a future ocean-observing constellation, targeting the Portuguese Atlantic region. AEROS features a miniaturized, high-resolution Hyperspectral Imager (HSI), a 5MP RGB camera, and a Software Defined Radio (SDR). The sensor generated data will be processed and aggregated for end-users in a new web-based Data Analysis Center (DAC). The HSI has 150 spectrally contiguous bands covering visible to near-infrared with 10 nm bandwidth. The HSI collects ocean color data to support studies of oceanographic characteristics known to influence the spatio-temporal distribution and movement behavior of marine organisms. Usage of an SDR expands AEROS's operational and communication range and allows for remote reconfiguration. The SDR receives, demodulates, and retransmits short duration messages, from sources including tagged marine organisms, autonomous vehicles, subsurface floats, and buoys. The future DAC will collect, store, process, and analyze acquired data, taking advantage of its ability to disseminate data across the stakeholders and the scientific network. Correlation of animal-borne Argos platform locations and oceanographic data will advance fisheries management, ecosystem-based management, monitoring of marine protected areas, and bio-oceanographic research in the face of a rapidly changing environment. For example, correlation of oceanographic data collected by the HSI, geolocated with supplementary images from the RGB camera and fish locations, will provide researchers with near real-time estimates of essential oceanographic variables within areas selected by species of interest.
... Combined EO and animal tracking data, allows researchers to investigate the mechanisms that drive those patterns. Researchers have identified multiple biotic and abiotic parameters such as SST, SSH, primary productivity, SSS, mesoscale oceanographic fronts and eddies, oceanographic currents, dissolved oxygen, and bathymetry to correlate with elasmobranch distribution in a dynamic environment [10]- [13]. The contribution from established EO missions still lack, however, the required spatial resolution for site or organism-level analyses [14]. ...
Full-text available
Preprint
AEROS aims to develop a nanosatellite as a precursor of a future system of systems, which will include assets and capabilities of both new and existing platforms operating in the Ocean and Space, equipped with state-of-the-art sensors and technologies, all connected through a communication network linked to a data gathering, processing and dissemination system. This constellation leverages scientific and economic synergies emerging from New Space and the opportunities in prospecting, monitoring, and valuing the Ocean in a sustainable manner, addressing the demand for improved spatial, temporal, and spectral coverage in areas such as coastal ecosystems management and climate change assessment and mitigation. Currently, novel sensors and systems, including a miniaturized hyperspectral imager and a flexible software-defined communication system, are being developed and integrated into a new versatile satellite structure, supported by an innovative on-board software. Additional sensors, like the LoRaWAN protocol and a wider field of view RGB camera, are under study. To cope with data needs, a Data Analysis Centre, including a cloud-based data and telemetry dashboard and a back-end layer, to receive and process acquired and ingested data, is being implemented to provide tailored-to-use remote sensing products for a wide range of applications for private and institutional stakeholders.
... The impact that turtle grazing has on their environment is likely accelerated further by the decline in large sharks that continues globally (Ferretti et al., 2010;Queiroz et al., 2019). Reports of seagrass overgrazing by turtles from Bermuda and Indonesia , both show seagrass meadows where predators are ecologically extinct (Heithaus et al., 2014). ...
Article
Large grazers (megaherbivores) have a profound impact on ecosystem functioning. However, how ecosystem multifunctionality is affected by changes in megaherbivore populations remains poorly understood. Understanding the total impact on ecosystem multifunctionality requires an integrative ecosystem approach, which is especially challenging to obtain in marine systems. We assessed the effects of experimentally simulated grazing intensity scenarios on ecosystem functions and multifunctionality in a tropical Caribbean seagrass ecosystem. As a model, we selected a key marine megaherbivore, the green turtle, whose ecological role is rapidly unfolding in numerous foraging areas where populations are recovering through conservation after centuries of decline, with an increase in recorded overgrazing episodes. To quantify the effects, we employed a novel integrated index of seagrass ecosystem multifunctionality based upon multiple, well-recognized measures of seagrass ecosystem functions that reflect ecosystem services. Experiments revealed that intermediate turtle grazing resulted in the highest rates of nutrient cycling and carbon storage, while sediment stabilization, decomposition rates, epifauna richness, and fish biomass are highest in the absence of turtle grazing. In contrast, intense grazing resulted in disproportionally large effects on ecosystem functions and a collapse of multifunctionality. These results imply that (i) the return of a megaherbivore can exert strong effects on coastal ecosystem functions and multifunctionality, (ii) conservation efforts that are skewed toward megaherbivores, but ignore their key drivers like predators or habitat, will likely result in overgrazing-induced loss of multifunctionality, and (iii) the multifunctionality index shows great potential as a quantitative tool to assess ecosystem performance. Considerable and rapid alterations in megaherbivore abundance (both through extinction and conservation) cause an imbalance in ecosystem functioning and substantially alter or even compromise ecosystem services that help to negate global change effects. An integrative ecosystem approach in environmental management is urgently required to protect and enhance ecosystem multifunctionality.
... Recent accumulation of fine-scale animal location data has provided unprecedented insights into habitat selection and spatial behavior at levels varying from the resource patch to the landscape scale (Jesmer et al., 2018;Kays et al., 2015;Strandburg-Peshkin et al., 2017). As a result, the understanding of behavioral and environmental factors that drive animal movement decisions in terrestrial and aquatic habitats has increased significantly (Queiroz et al., 2019;Tucker et al., 2018). However, this surge in animal space use research has seldom included detailed studies that combine both riparian and aquatic landscape variables. ...
Full-text available
Article
Neotropical freshwater habitats are particularly sensitive to degradation by human activity. Piscivorous semi‐aquatic freshwater megafauna inhabit both the terrestrial and aquatic mediums and thus may be good indicators of wetland habitat quality. However, the drivers of their space use at the terrestrial and aquatic landscape levels are not well understood. We studied the spatial behavior and habitat use of giant otters in Madre de Dios, Peru, inhabiting areas with variable levels of protection. We combined unmanned aerial vehicle (UAV) and satellite images to develop different terrestrial and water‐associated land cover variables. We tested the influence of these predictors on giant otter habitat use at multiple spatial scales, comparing used and available locations. Giant otters favored bank areas with dense forest canopy cover. In the aquatic medium, giant otters showed positive selection for open water and fallen logs and avoided floating vegetation. These findings may be explained by preference for optimal fish habitat to maximize foraging yield and bank areas that provide more cover from predators and higher quality denning locations. Variables developed from UAV images outperformed satellite‐derived variables. Despite recent signs of deforestation in lake banks in unprotected areas, spatial model predictions indicated that unprotected oxbow lakes did not differ in their habitat suitability from protected freshwater habitats. Management implications of our findings include identification of factors driving habitat suitability to guide policy and decisions regarding protection or restoration of oxbow lake ecosystems to support giant otter populations. In addition, we demonstrate that UAVs have value in complementing satellite‐derived images and providing a cost‐effective methodology to assess habitat quality for semi‐aquatic species at the land‐water interface.
... Elasmobranchs are one of the main predators of the world's oceans (Pacoureau et al., 2021). Shark population assessments for several regions have estimated that one-quarter of them are critically threatened mainly due to overexploitation, pollution, and ecological imbalances (Queiroz et al., 2019;Besnard et al., 2021). Globally, sharks are of high demand for human consumption and have declined by 71.1% between 1970 and 2018 due to an 18-fold increase in fishing activities (Pacoureau et al., 2021). ...
Article
Stable isotopic values of carbon (δ¹³C) and nitrogen (δ¹⁵N) were used to characterize the trophic structure and biomagnification of Cadmium (Cd), Mercury (Hg) and Selenium (Se) in a trophic web of 18 taxa namely zooplankton, crustaceans, mollusks, fishes, and Mustelus henlei shark collected off the western coast of Baja California Sur, Mexico. Isotopic results indicated interspecies variations in the trophic web structure with mean δ ¹³C values of – 20.0 ‰ (zooplankton) < − 18.2 ‰ (M. henlei) < − 14.1 ‰ (Thaisella kiosquiformis, mollusk). In general, δ¹⁵N and δ¹³C values increased from primary consumers (zooplankton) to predators, following the isotopic patterns of other trophic webs. The concentrations of Cd, Hg and Se were relatively less in most of the organisms except mollusks that presented high concentrations of Cd. The biomagnification factors of the trophic web showed biodilution of Cd (Food Web Magnification Factor, FWMFCd = 0.2), biomagnification of Hg (FWMFHg = 3.34) and Se (FWMFSe = 1.45) respectively. However, the concentrations of Se did not increase consistently from the lower trophic levels to the higher ones. This study documents the dynamics of a marine trophic structure and demonstrates that biodilution/biomagnification processes of metal contaminants are largely species specific and are closely related to physical - chemical and food web structure.
... The life histories of sharks and rays typically include restrictive features such as slow growth and low fecundity that make them particularly vulnerable to fishing pressure [1][2][3], and over a third of chondrichthyans are now threatened with extinction [4]. Understanding of reproductive behavior on fish movement and habitat selection has been recognized as crucial for proper management of teleost species [e.g., [5][6][7][8] but is far less understood in elasmobranchs. ...
Full-text available
Article
Understanding shark mating dynamics and mating site use may be vital to species management. The Dry Tortugas courtship and mating ground (DTCMG) has been known as a mating site for nurse sharks, Ginglymostoma cirratum, since 1895. In a 30-yr (1992-2021) study we have documented long-term site fidelity to this area with data from 137 adult sharks (89 female, 48 male) tagged with PIT, fin, and acoustic tags. Of 118 sharks tagged from 1993 to 2014, at least 80 (68%) returned to the DTCMG in subsequent years during the June-July mating season. Known individuals returned in up to 16 different mating seasons and over periods of up 28 years, indicating that life span extends well into the forties for this species. Of all returning sharks, 59% (N = 47) have been monitored for over 10 years and 13% (N = 10) have been monitored for over 20 years. Males arrived annually in May and June and departed in July, whereas females arrived biennially or triennially in June, with a secondary peak in site use in September and August, likely associated with thermoregula-tion during gestation. During the mating season, males made more frequent visits of shorter duration (median = 34 visits for 1 h per visit) to the DTCMG, whereas females made fewer visits but remained on site for longer periods (median = 12.5 visits for 4.4 h per visit). Females typically mated biennially but showed a triennial cycle in 32% of cases, with many females switching cycles at least once. This pattern would reduce the potential reproductive lifetime output of a female by 11% compared to what would be projected from a strict bien-nial cycle. The long-term mating site fidelity of this shark population reveals the importance of identifying and protecting mating sites for this and other elasmobranch species.
... Automatic Identification System (AIS) data provides valuable information about shipping activity in the oceans, revealing for example the appearance of new shipping routes (Eguíluz et al. 2016). In particular, concerning fishing vessels, global AIS analyses have provided inferences on the global distribution of fishing intensity , the unequal share of the industrial fishing effort among countries (McCauley et al. 2018), the economic impact of fishing in the high seas (Sala et al. 2018), the network of fishing ports supporting fishing activity in different ocean regions (Rodríguez et al. 2021), or the overlap with marine animals (Queiroz et al. 2019). ...
Full-text available
Preprint
Automated positioning devices can generate large datasets with information on the movement of humans, animals and objects, revealing patterns of movement, hot spots and overlaps among others. This information is obtained after cleaning the data from errors of different natures. However, in the case of Automated Information Systems (AIS), attached to vessels, these errors can come from intentional manipulation of the electronic device. Thus, the analysis of anomalies can provide valuable information on suspicious behaviour. Here, we analyse anomalies of fishing vessel trajectories obtained with the Automatic Identification System. The map of silence anomalies, those occurring when positioning data is absent for more than 24 h, shows that they occur more likely closer to land, observing 94.9% of the anomalies at less than 100 km from the shore. This behaviour suggests the potential of identifying silence anomalies as a proxy for illegal activities. With the increasing availability of high-resolution positioning of vessels and the development of powerful statistical analytical tools, we provide hints on the automatic detection of illegal activities that may help optimise monitoring, control and surveillance measures.
... Vandeperre et al. 2014a, Howey et al. 2017, and one study (Maxwell et al. 2019) re vealed that adult males and juvenile females partially overlap in some habitats in the northeastern Pacific. Although a recent tagging study described the migration pattern of pregnant blue sharks in the northwestern Pacific (Fujinami et al. 2021), information from satellite tags about the movements of blue sharks in the central and western North Pacific is lacking compared with other oceans (Queiroz et al. 2019). ...
Article
Spatial segregation is a key component to understand the ecology of highly migratory species; however, this aspect is poorly known for many pelagic shark species. We investigated spatial segregation by sex and life-history stage in blue sharks Prionace glauca in the northwestern Pacific, using satellite tracking data gathered from 74 electronic tags as well as fisheries-dependent size-measurement datasets, which allowed us to update a schematic diagram of the migration patterns of this population. Blue sharks were tracked for 30 to 271 d (mean 125 d) during which they moved extensively between temperate and subtropical waters. Juveniles were distributed mainly in the North Pacific Transition Zone (30–45° N), but expanded their range southward as they grew, while adults in the entire northwestern Pacific showed clear spatial segregation by sex. Adult females migrated seasonally between temperate and subtropical areas for reproduction, while adult males occupied broad distribution area yet mainly in temperate waters (30–40° N), and their habitats partially overlapped with those of juveniles of both sexes. These findings provide new insights for updating the schematic migration diagram of this population, especially because adult males were previously thought to distribute mainly in tropical and subtropical waters. Furthermore, a majority of adult females found north of 30° N exhibited fresh mating marks; this observation suggests that the mating ground of blue sharks in the northwestern Pacific is broader (20–40° N) than previously thought (20–30° N), and partially overlaps with the species' parturition and nursery grounds (30–50° N).
... Publicly available data for bycatch species in these fisheries are sparse, but some suggest that pelagic shark and rays make up the majority of their megafauna bycatch (Clarke et al., 2014;Hall & Roman, 2013). While comparable data are not readily available for other regions, available evidence suggests that elasmobranch catch is similarly high in other tuna fisheries (Clarke et al., 2013;Hall & Roman, 2013;Queiroz et al., 2019). Further, it is likely that pelagic elasmobranch bycatch is even higher than reported data for these fisheries due to poor compliance, low observer coverage and poor enforcement of reporting requirements (Babcock & Pikitch, 2011;Forget et al., 2021;Miyake et al., 2004;Oliver et al., 2015). ...
Full-text available
Article
The incidental capture by marine fisheries as bycatch poses a global threat to pelagic sharks and rays. In large, industrialized fisheries that often operate in areas beyond national jurisdiction, at least 22 threatened species of pelagic elasmobranchs are caught as bycatch, representing the majority of megafauna bycatch in tuna fisheries. Here, we investigate (1) the efficacy of the current policies of the five tuna‐related Regional Fisheries Management Organizations (tRFMOs) in mitigating elasmobranch bycatch, (2) data needed to better assess the amount and impact of elasmobranch bycatch and (3) the research necessary for the adoption of new policies. We found that tRFMOs have adopted 34 active policies that address pelagic elasmobranch bycatch. However, most policies (~76%, n = 26) are unlikely to avoid or minimize elasmobranch bycatch. Instead, most policies focus on mitigating post‐capture mortality via remediation and requiring or encouraging research and data collection. Despite the emphasis on research mandates, we find that the existence of research was not related to policy adoption, suggesting that lack of research has not historically prohibited policymaking. Overall, we suggest that current research and data transparency, though perhaps not necessary for policy adoption, are not sufficient to adequately evaluate the population‐level impacts of bycatch on many elasmobranch species in tRFMO‐managed fisheries. Given these results, we recommend a precautionary approach that involves reforms in tRFMO voting processes to facilitate the adoption of binding requirements for elasmobranch catch limits, bycatch avoidance, pre‐ and post‐capture handling and release modifications and protection of areas important to threatened pelagic elasmobranchs.
... Large obligate swimming fish (or ram ventilators), such as many large pelagic species, routinely encounter capture from recreational sports fishers (catch-and-release angling), as bycatch in global longline fisheries (e.g. protected elasmobranchs), or as part of management or research programmes [1,2]. In the field study of large free-ranging fishes, capture and release is required to attach animal-borne bio-loggers, which can directly measure swimming speed [3][4][5][6][7]. ...
... For most sharks, β ranges between a few negative thousandths [23] and a few positive hundredths [24]. 2 Formally, parasite drag is the drag at zero lift and it mainly comprises of the friction between the body and the water; induced drag is the cost of generating hydrodynamic lift. 3 The first term in this equation is the potential energy of the swimmer; it has a negative sign because depth is the greatest at the nadir. ...
Full-text available
Article
Marine organisms normally swim at elevated speeds relative to cruising speeds only during strenuous activity, such as predation or escape. We measured swimming speeds of 29 ram ventilating sharks from 10 species and of three Atlantic bluefin tunas immediately after exhaustive exercise (fighting a capture by hook-and-line) and unexpectedly found all individuals exhibited a uniform mechanical response, with swimming speed initially two times higher than the cruising speeds reached approximately 6 h later. We hypothesized that elevated swimming behaviour is a means to increase energetic demand and drive the removal of lactate accumulated during capture via oxidation. To explore this hypothesis, we estimated the mechanical work that must have been spent by an animal to elevate its swim speed and then showed that the amount of lactate that could have been oxidized to fuel it comprises a significant portion of the amount of lactate normally observed in fishes after exhaustive exercise. An estimate for the full energetic cost of the catch-and-release event ensued.