Movements Of Sharks Research Articles

Scalloped Hammerhead (Sphyrna lewini) Movement Behavior toward Diver in Banda Waters, Maluku

Shark diving tourism opens opportunities to study shark behavior towards diver. As one of the popular attractions for the marine tourism in Indonesia, shark diving play significant role for the conservation in the eastern part of Indonesia. Banda Sea, as well as Morotai, Derawan, Raja Ampat, Nabire and Teluk Cenderawasih, Bali, Lombok, Komodo, and Gorontalo, is famous for its shark diving attraction. Despite its famous status as a tourism attraction, little is known about the behavior of scalloped hammerhead shark during the interaction with Self-Contained Underwater Breathing Apparatus (SCUBA) diver. The information of scalloped hammerhead shark movement behavior during interaction with SCUBA diver is important for developing ecological assessment, safe diving practice, and shark tourism carrying capacity. This research involves DOV (Diver Operated Video) to record the movement patterns of shark while interacting with SCUBA Diver. Evaluation of approximately 457 photos and 32 videos of the Sphyrna lewini during 14 days of observations has been analyzed during SCUBA diving shows the most common shark agonistic display: pectoral fins depression - apart from other displays such as tail slapping, flank displaying, charging, snout raise, and jaw gapping. It also reveals three (3) new shark agonistic postures which were never been recorded previously: charging, snout raise, and jaw gapping. This study showed that there are consistent behaviors observed while meeting with SCUBA divers and this may be beneficial for development of safety diving management, as well as conservation efforts.

Spatial Dynamics and Fine-Scale Vertical Behaviour of Immature Eastern Australasian White Sharks (Carcharodon carcharias).

Knowledge of the 3-dimensional space use of large marine predators is central to our understanding of ecosystem dynamics and for the development of management recommendations. Horizontal movements of white sharks, Carcharodon carcharias, in eastern Australian and New Zealand waters have been relatively well studied, yet vertical habitat use is less well understood. We dual-tagged 27 immature white sharks with Pop-Up Satellite Archival Transmitting (PSAT) and acoustic tags in New South Wales coastal shelf waters. In addition, 19 of these individuals were also fitted with Smart Position or Temperature Transmitting (SPOT) tags. PSATs of 12 sharks provided useable data; four tags were recovered, providing highly detailed archival data recorded at 3-s intervals. Horizontal movements ranged from southern Queensland to southern Tasmania and New Zealand. Sharks made extensive use of the water column (0-632 m) and experienced a broad range of temperatures (7.8-28.9 °C). Archival records revealed pronounced diel-patterns in distinct fine-scale oscillatory behaviour, with sharks occupying relatively constant depths during the day and exhibiting pronounced yo-yo diving behaviour (vertical zig-zag swimming through the water column) during the night. Our findings provide valuable new insights into the 3-dimensional space use of Eastern Australasian (EA) white sharks and contribute to the growing body on the general ecology of immature white sharks.

Preliminary Data about Habitat Use of Subadult and Adult White Sharks (Carcharodon carcharias) in Eastern Australian Waters.

Simple SummaryIn eastern Australia, the movement of subadult and adult white sharks is poorly understood as very few animals are encountered. To investigate how deep they dive, where they travel and water temperatures they live in, we tagged three white sharks (340–388 cm total length) between May 2021 and January 2022. All sharks moved away from the coast after release and preferred offshore habitats. The three sharks mainly stayed within 50 m of the surface, in water temperatures between 14–19 °C and dived deeper during the day. They all moved north–south along the coastline and spent little time in the same location but there was evidence that they stayed in some locations longer than others. Very little information is available for adult white sharks in eastern Australia and studies like this provide key information about their preferences. As they travel long distances it is important for multijurisdictional management to effectively mitigate human-shark interactions whilst supporting conservation efforts.In eastern Australia, white sharks (Carcharodon carcharias) are targeted in shark control programs, yet the movement of subadults and adults of the eastern Australasian population is poorly understood. To investigate horizontal and vertical movement and habitat use in this region, MiniPAT pop-up satellite archival tags were deployed on three larger white sharks (340–388 cm total length) between May 2021 and January 2022. All sharks moved away from the coast after release and displayed a preference for offshore habitats. The upper < 50 m of the water column and temperatures between 14–19 °C were favoured, with a diel pattern of vertical habitat use evident as deeper depths were occupied during the day and shallower depths at night. Horizontal movement consisted of north–south seasonality interspersed with periods of residency. Very little information is available for adult white sharks in eastern Australia and studies like this provide key baseline information for their life history. Importantly, the latitudinal range achieved by white sharks illuminate the necessity for multijurisdictional management to effectively mitigate human-shark interactions whilst supporting conservation efforts of the species.

Multi-year acoustic tracking reveals transient movements, recurring hotspots, and apparent seasonality in the coastal-offshore presence of Greenland sharks (Somniosus microcephalus)

Variable movement strategies can complicate the conservation and management of mobile species. Given its extreme life history traits as a long-lived, deep-water species, the Greenland shark (Somniosus microcephalus) is vulnerable to fisheries bycatch, but little is known over its long-term movements across a spatially and seasonally variable Arctic environment. To address this knowledge gap, the movements of Greenland sharks in coastal fjords and offshore waters of Baffin Bay were examined using seven years of acoustic telemetry data. Seasonal patterns in broad-scale movements and inshore-offshore connectivity were compared among 155 sharks (101 males, 54 females [mean LT = 2.65 ± 0.48 m, range 0.93-3.5 m]) tagged in 6 discrete coastal locations spanning from Grise Fiord to Cumberland Sound (Nunavut). Sharks exhibited transient movements throughout coastal and offshore regions with some evidence of seasonally recurring hotspots revealed by repeat detections of individuals at sites over multiple years. Shark presence in coastal fjords occurred exclusively during the coastal ice-free period (July to November), regardless of the location of tagging or detection, while presence in the offshore was recorded during the period of ice re-formation and cover (November to July). Through multi-year telemetry, it was possible to reveal repetitive patterns in broad-scale habitat use for a complex marine predator with direct relevance for understanding the seasonal distribution of mobile Arctic consumers and informing regional fisheries management.

Active acoustic telemetry reveals ontogenetic habitat-related variations in the coastal movement ecology of the white shark

BackgroundLittle is known about the fine-scale behavioural choices white sharks make. The assessment of movement at high spatio-temporal resolution can improve our understanding of behavioural patterns. Active acoustic telemetry was used along a coastal seascape of South Africa to investigate the movement-patterns of 19 white sharks tracked for 877 h within habitats known to host different prey types.ResultsA three-state hidden Markov model showed higher ontogenetic variability in the movements of white sharks around estuary-related coastal reef systems compared to around a pinniped colony. Our results further suggest white sharks (1) use the same searching strategy in areas where either pinnipeds or fishes are present; (2) occupy sub-tidal reef habitats possibly for either conserving energy or recovering energy spent hunting, and (3) travel directly between the other two states.ConclusionsWhite sharks appear not to simply roam coastal habitats, but rather adopt specific temporally optimized behaviours associated with distinct habitat features. The related behaviours are likely the result of a balance among ontogenetic experience, trophic niche, and energetics, aimed at maximizing the use of temporally and spatially heterogeneous environments and resources. The possible implications for the future conservation of white sharks in coastal areas are discussed, with particular attention to South Africa’s present conservation and management challenges.

First descriptions of the seasonal habitat use and residency of scalloped hammerhead (Sphyrna lewini) and Galapagos sharks (Carcharhinus galapagensis) at a coastal seamount off Japan

BackgroundThe Northwestern Pacific is a data-poor region for studies into the movements and habitat use of open ocean and pelagic sharks. However, this region experiences considerable pressure from commercial fishing. Therefore, shark movement data from this region carry significant implications for conservation and management, particularly for threatened species. Here, we provide the first data on seasonal residency and movements of scalloped hammerhead (Sphyrna lewini) and Galapagos sharks (Carcharhinus galapagensis), using acoustic and satellite telemetry, and dive logbooks, off Japan.ResultsEight female sharks, four of each species, were tagged around a coastal seamount off southeastern Japan (Mikomoto Island) in August 2015, and monitored for a period of up to 363 days using an array of six receivers around the island. Analyses of the more abundant scalloped hammerhead acoustic data suggest high seasonal residency predominantly from August to November associated with lower chlorophyll-a concentrations, before sharks then leave the island and return the following summer. Residency for scalloped hammerhead sharks were highest among those receivers closest to the Kuroshio Current, which produces strong coastal upwelling, however SST was not found to be predictive of occurrence at Mikomoto. Shark presence was corroborated by analysis of dive-log data from a local ecotourism operator. We also produced two unique satellite tracks, whereby a scalloped hammerhead exhibited a 200-km dispersal into a coastal embayment west of the tagging location and a Galapagos shark migrated over 800 km offshore into the high seas.ConclusionThis study provided some of the first behavioral and movement data for scalloped hammerhead and Galapagos sharks in Japan. Our findings suggest varying spatial and temporal visitation of two shark species to a coastal seamount, underscored by some degree of seasonal residency and site fidelity and linked, for scalloped hammerhead sharks at least, to varying productivity. Furthermore, we provided preliminary evidence for long-distance dispersal of these species, and some site fidelity to seamounts in the region. This study highlights the importance of describing shark movements to aid in filling critical data gaps for poorly understood, endemic populations of threatened species.

Global collision-risk hotspots of marine traffic and the world’s largest fish, the whale shark

Marine traffic is increasing globally yet collisions with endangered megafauna such as whales, sea turtles, and planktivorous sharks go largely undetected or unreported. Collisions leading to mortality can have population-level consequences for endangered species. Hence, identifying simultaneous space use of megafauna and shipping throughout ranges may reveal as-yet-unknown spatial targets requiring conservation. However, global studies tracking megafauna and shipping occurrences are lacking. Here we combine satellite-tracked movements of the whale shark, Rhincodon typus, and vessel activity to show that 92% of sharks’ horizontal space use and nearly 50% of vertical space use overlap with persistent large vessel (>300 gross tons) traffic. Collision-risk estimates correlated with reported whale shark mortality from ship strikes, indicating higher mortality in areas with greatest overlap. Hotspots of potential collision risk were evident in all major oceans, predominantly from overlap with cargo and tanker vessels, and were concentrated in gulf regions, where dense traffic co-occurred with seasonal shark movements. Nearly a third of whale shark hotspots overlapped with the highest collision-risk areas, with the last known locations of tracked sharks coinciding with busier shipping routes more often than expected. Depth-recording tags provided evidence for sinking, likely dead, whale sharks, suggesting substantial “cryptic” lethal ship strikes are possible, which could explain why whale shark population declines continue despite international protection and low fishing-induced mortality. Mitigation measures to reduce ship-strike risk should be considered to conserve this species and other ocean giants that are likely experiencing similar impacts from growing global vessel traffic.

Tidal and diel effects on the movement and space use of bull sharks (Carcharhinus leucas) and bonnetheads (Sphyrna tiburo) in a Florida Estuary

Tidal and diel effects on the movement and space use of bull sharks (Carcharhinus leucas) and bonnetheads (Sphyrna tiburo) in a Florida Estuary

Sex and Size Influence the Spatiotemporal Distribution of White Sharks, With Implications for Interactions With Fisheries and Spatial Management in the Southwest Indian Ocean

Human activities in the oceans increase the extinction risk of marine megafauna. Interventions require an understanding of movement patterns and the spatiotemporal overlap with threats. We analysed the movement patterns of 33 white sharks (Carcharodon carcharias) satellite-tagged in South Africa between 2012 and 2014 to investigate the influence of size, sex and season on movement patterns and the spatial and temporal overlap with longline and gillnet fisheries and marine protected areas (MPAs). We used a hidden Markov model to identify ‘resident’ and ‘transient’ movement states and investigate the effect of covariates on the transition probabilities between states. A model with sex, total length and season had the most support. Tagged sharks were more likely to be in a resident state near the coast and a transient state away from the coast, while the probability of finding a shark in the transient state increased with size. White sharks moved across vast areas of the southwest Indian Ocean, emphasising the need for a regional management plan. White sharks overlapped with longline and gillnet fisheries within 25% of South Africa’s Exclusive Economic Zone and spent 15% of their time exposed to these fisheries during the study period. The demersal shark longline fishery had the highest relative spatial and temporal overlap, followed by the pelagic longline fishery and the KwaZulu-Natal (KZN) shark nets and drumlines. However, the KZN shark nets and drumlines reported the highest white shark catches, emphasising the need to combine shark movement and fishing effort with reliable catch records to assess risks to shark populations accurately. White shark exposure to shark nets and drumlines, by movement state, sex and maturity status, corresponded with the catch composition of the fishery, providing support for a meaningful exposure risk estimate. White sharks spent significantly more time in MPAs than expected by chance, likely due to increased prey abundance or less disturbance, suggesting that MPAs can benefit large, mobile marine megafauna. Conservation of white sharks in Southern Africa can be improved by implementing non-lethal solutions to beach safety, increasing the observer coverage in fisheries, and continued monitoring of movement patterns and existing and emerging threats.

Estimated life-history traits and movements of the Caribbean reef shark (Carcharhinus perezi) in The Bahamas based on tag-recapture data

Estimated life-history traits and movements of the Caribbean reef shark (Carcharhinus perezi) in The Bahamas based on tag-recapture data

Spatio-Temporal Variability in White Shark (Carcharodon carcharias) Movement Ecology During Residency and Migration Phases in the Western North Atlantic

Understanding how mobile, marine predators use three-dimensional space over time is central to inform management and conservation actions. Combining tracking technologies can yield powerful datasets over multiple spatio-temporal scales to provide critical information for these purposes. For the white shark (Carcharodon carcharias), detailed movement and migration information over ontogeny, including inter- and intra-annual variation in timing of movement phases, is largely unknown in the western North Atlantic (WNA), a relatively understudied area for this species. To address this need, we tracked 48 large juvenile to adult white sharks between 2012 and 2020, using a combination of satellite-linked and acoustic telemetry. Overall, WNA white sharks showed repeatable and predictable patterns in horizontal movements, although there was variation in these movements related to sex and size. While most sharks undertook an annual migratory cycle with the majority of time spent over the continental shelf, some individuals, particularly adult females, made extensive forays into the open ocean as far east as beyond the Mid-Atlantic Ridge. Moreover, increased off-shelf use occurred with body size even though migration and residency phases were conserved. Summer residency areas included coastal Massachusetts and portions of Atlantic Canada, with individuals showing fidelity to specific regions over multiple years. An autumn/winter migration occurred with sharks moving rapidly south to overwintering residency areas in the southeastern United States Atlantic and Gulf of Mexico, where they remained until the following spring/summer. While broad residency and migration periods were consistent, migratory timing varied among years and among individuals within years. White sharks monitored with pop-up satellite-linked archival tags made extensive use of the water column (0–872 m) and experienced a broad range of temperatures (−0.9 – 30.5°C), with evidence for differential vertical use based on migration and residency phases. Overall, results show dynamic inter- and intra-annual three-dimensional patterns of movements conserved within discrete phases. These results demonstrate the value of using multiple tag types to track long-term movements of large mobile species. Our findings expand knowledge of the movements and migration of the WNA white shark population and comprise critically important information to inform sound management strategies for the species.

Forecasting intraspecific changes in distribution of a wide-ranging marine predator under climate change

Globally, marine animal distributions are shifting in response to a changing climate. These shifts are usually considered at the species level, but individuals are likely to differ in how they respond to the changing conditions. Here, we investigate how movement behaviour and, therefore, redistribution, would differ by sex and maturation class in a wide-ranging marine predator. We tracked 115 tiger sharks (Galeocerdo cuvier) from 2002 to 2020 and forecast class-specific distributions through to 2030, including environmental factors and predicted occurrence of potential prey. Generalised Linear and Additive Models revealed that water temperature change, particularly at higher latitudes, was the factor most associated with shark movements. Females dispersed southwards during periods of warming temperatures, and while juvenile females preferred a narrow thermal range between 22 and 23 °C, adult female and juvenile male presence was correlated with either lower (< 22 °C) or higher (> 23 °C) temperatures. During La Niña, sharks moved towards higher latitudes and used shallower isobaths. Inclusion of predicted distribution of their putative prey significantly improved projections of suitable habitats for all shark classes, compared to simpler models using temperature alone. Tiger shark range off the east coast of Australia is predicted to extend ~ 3.5° south towards the east coast of Tasmania, particularly for juvenile males. Our framework highlights the importance of combining long-term movement data with multi-factor habitat projections to identify heterogeneity within species when predicting consequences of climate change. Recognising intraspecific variability will improve conservation and management strategies and help anticipate broader ecosystem consequences of species redistribution due to ocean warming.

Behavioural response of a whale shark during the passage of a typhoon.

During a behavioural survey of a tagged whale shark (Rhincodon typus) conducted in 2019 in the waters off Kagoshima, Japan, a typhoon passed close to the area under surveillance. As the typhoon approached, monitoring of the shark's movements indicated that it dived to depths of up to 90 m, and during this period, the authors recorded the effects of the typhoon-induced waves. They also detected changes in the vertical thermal structure of the waters, possibly due to the disturbance caused by the typhoon.

Comprehensive analytical approaches reveal species‐specific search strategies in sympatric apex predatory sharks

Animals follow specific movement patterns and search strategies to maximize encounters with essential resources (e.g. prey, favourable habitat) while minimizing exposures to suboptimal conditions (e.g. competitors, predators). While describing spatiotemporal patterns in animal movement from tracking data is common, understanding the associated search strategies employed continues to be a key challenge in ecology. Moreover, studies in marine ecology commonly focus on singular aspects of species' movements, however using multiple analytical approaches can further enable researchers to identify ecological phenomena and resolve fundamental ecological questions relating to movement. Here, we used a set of statistical physics‐based methods to analyze satellite tracking data from three co‐occurring apex predators (tiger, great hammerhead and bull sharks) that predominantly inhabit productive coastal regions of the northwest Atlantic Ocean and Gulf of Mexico. We analyzed data from 96 sharks and calculated a range of metrics, including each species' displacements, turning angles, dispersion, space‐use and community‐wide movement patterns to characterize each species' movements and identify potential search strategies. Our comprehensive approach revealed high interspecific variability in shark movement patterns and search strategies. Tiger sharks displayed near‐random movements consistent with a Brownian strategy commonly associated with movements through resource‐rich habitats. Great hammerheads showed a mixed‐movement strategy including Brownian and resident‐type movements, suggesting adaptation to widespread and localized high resource availability. Bull sharks followed a resident movement strategy with restricted movements indicating localized high resource availability. We hypothesize that the species‐specific search strategies identified here may help foster the co‐existence of these sympatric apex predators. Following this comprehensive approach provided novel insights into spatial ecology and assisted with identifying unique movement and search strategies. Similar future studies of animal movement will help characterize movement patterns and also enable the identification of search strategies to help elucidate the ecological drivers of movement and to understand species' responses to environmental change.

Continental-Scale Network Reveals Cross-Jurisdictional Movements of Sympatric Sharks With Implications for Assessment and Management

Understanding the movement ecology of marine species and connectivity of populations is required for effective fisheries management. This is especially the case for species with wide-ranging distributions for which movement can span across several jurisdictions with different management regulations. We used the Australian national network of acoustic receivers facilitated by the Integrated Marine Observing System (IMOS) to describe the extent and frequency of movements for two large epipelagic shark species, the bronze whaler (Carcharhinus brachyurus) and dusky shark (Carcharhinus obscurus). A total of 210 sharks (117 bronze whalers and 93 dusky sharks) were tracked for a 10-year period during which 21% and 9% of detected bronze whalers and dusky sharks, respectively, moved between Australian states. Bronze whalers showed more variable inter-state movements, mostly between Western Australia and South Australia but also eastwards to New South Wales (NSW). Although no dusky sharks tagged in Western Australia undertook inter-state movements, ∼50% of the sharks tagged in South Australia went to Western Australia. Five of the 14 dusky sharks tagged in NSW (36%) were detected across different states but remained on the east and southeast coasts (Queensland, NSW, Victoria, and Tasmania). The IMOS receivers also detected six bronze whalers in Ningaloo Reef, representing an extension of the previously known Australian distribution. Our findings highlight the value of collaboration between researchers and the value of national infrastructure, by providing a more accurate understanding of inter-state movements. This new information will allow the development of more adequate population dynamic models for stock assessment and management advice, requiring collaboration among state agencies for coordinating research activities, sharing data and resources, and establishing appropriate cross-jurisdictional policies. This is essential to achieve successful management and conservation outcomes for highly migratory species.

Horizontal and vertical movements of immature dusky sharks Carcharhinus obscurus in relation to commercial longline fisheries in the western North Atlantic Ocean

BackgroundMany species of sharks, including the dusky shark Carcharhinus obscurus, are often incidentally captured in commercial pelagic and bottom longline fisheries. Incidental capture can lead to at-vessel or post-release mortality and can be detrimental to populations of threatened, endangered, or prohibited species. The estimated at-vessel mortality for dusky sharks can be high in longline fisheries and, to minimize mortality, time–area closures have been designated in the western North Atlantic Ocean to mitigate interactions with longline fisheries, yet incidental capture of dusky sharks is still common. We compared the vertical and horizontal movements of dusky sharks to the overall fishing effort and depth fished of commercial pelagic and bottom longline fisheries to determine when and where overlap is present that could lead to incidental capture.ResultsTwenty-one (n = 21) dusky sharks were tagged with pop-up archival transmitting satellite tags and all were immature animals (123–200 cm FL) apart from two individuals (230 and 300 cm FL). Sharks were tagged off the coasts of North Carolina (71%) and Florida (29%). Twenty tags (95%) reported and provided tracks between 1 and 107 days (median 15 days) and 10 tags (50%) remained on sharks for > 4 days. Most individuals remained within the bottom longline closed area off the coast of North Carolina during their time at liberty. Dusky sharks primarily occupied the 20–40 m depth range 26% of the time, and overlapped with bottom and pelagic longline gears 41% and 59% of the time, respectively. Overlap was highest in the winter and spring for both commercial fisheries.ConclusionsThe use of archival satellite telemetry in this study has provided valuable preliminary information on vertical and horizontal movements of immature dusky sharks in western North Atlantic Ocean. Dusky sharks may be more vulnerable to incidental capture in the pelagic longline fishery due to the high fishing effort, larger areas of horizontal overlap, and greater percentage of vertical overlap. This information will inform mitigation measures of commercial longline fisheries, which can work toward population rebuilding of the species.

Stable Isotope Analysis of Juvenile White Sharks Inside a Nursery Area Reveals Foraging in Demersal-Inshore Habitats and Trophic Overlap With Sympatric Sharks

Knowledge about top predators’ trophic ecology is crucial for defining their role in ecosystems, understanding habitat preferences, characterizing life stage-specific feeding habits, and evaluating their interaction with fisheries. In the northeastern Pacific, white sharks (Carcharodon carcharias) occupy coastal habitats during the early life stages, including Bahía Sebastián Vizcaíno (BSV) in Mexico, which is a known nursery area. Although BSV presumably provides high prey abundance, the trophic ecology of immature white sharks is poorly understood. Carbon and nitrogen bulk stable isotope analyses (SIA) were used to explore the trophic relationship of early life stages with their potential prey and to infer dietary overlap with sympatric sharks, while SIA of amino acids were used to estimate trophic position. Muscle samples from young white sharks and inshore demersal prey commonly found in their stomach contents were sampled. Demersal prey and literature-derived isotope ratios for pelagic and offshore species were incorporated into mixing models with a Bayesian framework to estimate their contribution to white shark tissues. Nearshore demersal prey had the highest contribution for all life stages (between 35 and 47%), consistent with previous reports based on gut content analysis. The contribution of pelagic (between 26 and 37%) and offshore (between 14 and 32%) prey was smaller and suggests potential periodic changes in foraging grounds and the presence of a maternal-derived isotopic signature. A high contribution of demersal prey indicates a high level of interaction with local fisheries that target those species and catch white sharks incidentally and is consistent with immature shark movement patterns. Isotope ratios of two sympatric sharks, smooth hammerhead Sphyrna zygaena and copper sharks Carcharhinus brachyurus, were used to estimate the overlap in isotopic niche space. Immature white sharks had the smallest isotopic niche, while the highest was for copper sharks. Overlap was greatest between white sharks and hammerheads (∼45%), while overlap with copper sharks was limited (&amp;lt;20%), suggesting less potential for competition. Trophic position estimates were similar to those previously reported for the species. These results highlight the importance of coastal demersal prey heavily targeted by local fisheries for the diet of young white sharks and support the importance of BSV as a nursery habitat.

Dynamic use of coastal areas by bull sharks and the conciliation of conservation and management of negative human–wildlife interactions

Abstract Knowledge about spatial and temporal variability in the distribution and abundance of predators is necessary to adapt measures to mitigate human–wildlife interactions. Acoustic telemetry and network analyses were used to investigate the spatial ecology of bull sharks, the species responsible for most shark bites in Reunion Island, one of the world's shark bite hotspots. The west coast of the island was not used uniformly by every individual, with size predicting the movements of sharks along the coast. Node‐based metrics – closeness, node strength, and cumulated continuous residency times – derived from up to 181 monthly movement networks from 20 individuals, revealed that smaller sharks (&lt;250 cm total length) primarily used the south‐west coast while larger individuals spent most of their time in the northern region with regular visits to multiple areas along the coast. This study provides essential knowledge on bull shark behaviour and central areas used at different periods of the year, which correlates well with the dynamics of observed shark bites. Our approach provides a non‐invasive alternative to help predicting and anticipating human–shark conflicts and avoid shark culling programmes detrimental to the conservation of large predators such as sharks.

First Insights Into the Horizontal Movements of Whale Sharks (Rhincodon typus) in the Northern Arabian Sea

Whale sharks off the western coast of India have suffered high levels of fishing pressure in the past, and today continue to be caught in small-scale fisheries as by-catch. Additionally, coastlines in this region host very large and growing human populations that are undergoing rapid development. This exacerbates ongoing anthropogenic threats to this species such as pollution, habitat loss, and ship traffic. For these reasons, there is an urgent need for data on movement patterns of whale sharks in this region of the Indian Ocean. Here, we address this issue by providing the first data on the horizontal movements of whale sharks tagged in the northern Arabian Sea off the western coast of the Indian state of Gujarat. From 2011 to 2017, eight individuals, ranging from 5.4 to 8 m were tagged and monitored using satellite telemetry. Tag retention varied from 1 to 137 days, with the sharks traveling distances of 34 – ∼2,230 km. Six of the eight individuals remained close to their tagging locations, although two sharks displayed wide ranging movements into the Arabian Sea, following frontal zones between water masses of different sea surface temperatures. We explore the relationship between the movement patterns of these whale sharks and the physical and biological processes of the region.

Movement of the bull shark (Carcharhinus leucas) in the upper Mississippi River Basin, North America

Rare appearances of bull sharks (Carcharhinus leucas) in river systems and other freshwater ecosystems have been reported from five continents. The wide geographic range of this phenomenon, the physiological adaptations of this species to allow for movement into rivers, and a fossil record in the Miocene Epoch, all imply that this behavior has a long history. In the Mississippi River basin, however, only two specimens were captured in the river’s upper portion during the entire 20th century. Further historical, archeological, and paleontological records of these animals appearing farther than 500 km upstream from the Mississippi delta is almost nonexistent. Bull shark movements in the upper portions of this river are likely sufficiently rare or cryptic to avoid detection using historical, archaeological, paleontological, and modern fisheries conservation techniques. Deeper research into these sharks, and their historical biogeography is needed to better understand the relationship these large predators have to the freshwater ecosystems of the American mid-continent.