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This opinion piece presents empirical evidence to examine possible negative consequences of the use of penetrative tagging as used on the great white shark (GWS). Tagging programs currently using this method attach SPOT (Spatial Positioning Only Tags) using corrodible bolts inserted through the dorsal fin while the shark is taken out of water. Such methods can cause harm to the tagged individual. Possible adverse effects include impacts on growth, tag biofouling, wounds, heightened stress, and hemorrhaging. This method may adversely impact dorsal fin structure and the shark's hydrodynamics. As a result, data collected may not be reflective of natural behavior. Bolted SPOT are semi-permanently affixed to the shark but can have a battery life of approximately 3.5 years. Most of these tags (69%) ceased transmitting in less than 2 years. Alternative tagging technologies exist as more humane options. [ABSTRACT FROM AUTHOR]

The narrownose smooth-hound, Mustelus schmitti (Carcharhiniformes, Triakidae) is an endemic shark of the southwest Atlantic Ocean and it is listed as critically endangered by the IUCN. The age and growth of M. schmitti were studied using vertebrae of 102 females and 121 males caught as by-catch by the bottom-trawl shrimp fishery and by coastal sport anglers in Central Patagonia (43-44° S). The maximum ages observed for females and males were 18 and 16 years, respectively. Seven growth (size-at-age) models were fitted. The two-phase von Bertalanffy model presented the best fit for females and males. There were no differences in growth between sexes. Growth parameters were asymptotic length (L∞)=916 mm; growth coefficient (k)=0.12 years-1; age at which the transition between the two growth phases occurs (th)=5.26 years; length at birth (L0)=283.03 mm, and longevity (tmax)=21.92 years. The age at sexual maturity was estimated at 8.86 and 8.48 years for females and males, respectively. M. schmitti exhibits moderate growth, relatively long lifespan and late maturity, like other elasmobranchs characterized as extremely vulnerable. [ABSTRACT FROM AUTHOR]

Sharks rubbing against ocean floor or rocks are common events in marine environments, while instances of interspecific shark chafing behavior have been observed much less frequently. This behavior has garnered scientific interest in recent years and usually involves a smaller shark rubbing against a larger species, utilizing dermal denticles to rid itself of parasites or dead skin cells. Despite the costs and benefits of this behavior being not yet fully understood, we report new evidence of grey reef sharks (Carcharhinus amblyrhynchos Bleeker, 1856) engaging in chafing behavior against whale shark (Rhincodon typus Smith, 1828) in the Maldives. This behavior suggests that grey reef sharks may engage in chasing behavior for cleaning purposes or take advantage of larger sharks as an anti-predation tactic. These records contribute to shed light on previously unexplored aspects of elasmobranch interspecies interactions and highlight the need for further research into this topic. The prevalence of such behavior across different regions suggests its potential significance in the ecological dynamics of shark population. [ABSTRACT FROM AUTHOR]

This opinion piece presents empirical evidence to examine possible negative consequences of the use of penetrative tagging as used on the great white shark (GWS). Tagging programs currently using this method attach SPOT (Spatial Positioning Only Tags) using corrodible bolts inserted through the dorsal fin while the shark is taken out of water. Such methods can cause harm to the tagged individual. Possible adverse effects include impacts on growth, tag biofouling, wounds, heightened stress, and hemorrhaging. This method may adversely impact dorsal fin structure and the shark’s hydrodynamics. As a result, data collected may not be reflective of natural behavior. Bolted SPOT are semi-permanently affixed to the shark but can have a battery life of approximately 3.5 years. Most of these tags (69%) ceased transmitting in less than 2 years. Alternative tagging technologies exist as more humane options.

The article reports that a group of United Kingdom and Portuguese scientists went on a sea expedition to study the impact of ocean deoxygenation on marine life, including sharks. Topics include deoxygenation caused by climate change, which is warming surface waters and reducing amount of oxygen in the ocean; and scientists' insights on the significant impact of deoxygenation on marine life than ocean acidification or marine heat waves noticed a link between shark behavior and oxygen levels.

In recent years, much attention has been focused on the impact of climate change, particularly via ocean acidification (OA), on marine organisms. Studying the impact of OA on long-living organisms, such as sharks, is especially challenging. When the ocean waters absorb anthropogenic carbon dioxide (CO2), slow-growing shark species with long generation times may be subjected to stress, leading to a decrease in functionality. Our goal was to examine the behavioral and physiological responses of sharks to OA and the possible impacts on their fitness and resilience. We conducted a systematic review in line with PRISMA-Analyses, of previously reported scientific experiments. We found that most studies used CO2 partial pressures (pCO2) that reflect representative concentration pathways for the year 2100 (e.g., pH ~7.8, pCO2 ~1000 μatm). Since there is a considerable knowledge gap on the effect of OA on sharks, we utilized existing data on bony fish to synthesize the available knowledge. Given the similarities between the behaviors and physiology of these two superclasses' to changes in CO2 and pH levels, there is merit in including the available information on bony fish as well. Several studies indicated a decrease in shark fitness in relation to increased OA and CO2 levels. However, the decrease was species-specific and influenced by the intensity of the change in atmospheric CO2 concentration and other anthropogenic and environmental factors (e.g., fishing, temperature). Most studies involved only limited exposure to future environmental conditions and were conducted on benthic shark species studied in the laboratory rather than on apex predator species. While knowledge gaps exist, and more research is required, we conclude that anthropogenic factors are likely contributing to shark species' vulnerability worldwide. However, the impact of OA on the long-term stability of shark populations is not unequivocal. [ABSTRACT FROM AUTHOR]

Multisensor biologging provides a powerful tool for ecological research, enabling fine-scale observation of animals to directly link physiology and movement to behavior across ecological contexts. However, applied research into behavioral disturbance and recovery following human interventions (e.g., capture and translocation) has mostly relied on coarse location-based tracking or unidimensional approaches (e.g., dive profiles and activity/energetic metrics) that may not resolve behaviors and recovery processes. Biologging can improve insights into both disturbed and natural behavior, which is critical for management and conservation initiatives, although challenges remain in objectively identifying distinct behavioral modes from complex multisensor datasets. Using white sharks (Carcharodon carcharias) released from a non-lethal catch-and-release shark bite mitigation program, we explored how combining multisensor biologging (video, depth, accelerometers, gyroscopes, and magnetometers), track reconstruction and behavioral state modeling using hidden Markov models (HMMs) can improve our understanding of behavioral processes and recovery. Biologging tags were deployed on eight white sharks, recording their continuous behaviors, movements, and environmental context (habitat, interactions with other organisms/objects) for periods of 10–87 h post-release. Dive profiles and tailbeat analysis (as a standard, activity-based method for assessing recovery) indicated an immediate “disturbed” period of offshore movement, displaying rapid tailbeats and an average tailbeat-derived recovery period of 9.7 h, with evidence of smaller individuals having longer recoveries. However, further integrating magnetometer-derived headings, track reconstruction and HMM modeling revealed a cryptic shift to diurnal clockwise-counterclockwise circling behavior, which we argue represents compelling new evidence for hypothesized unihemispheric sleep amongst elasmobranchs. By simultaneously providing critical information toward conservation-focused shark management and understudied aspects of shark behavior, our study highlights how integrating multisensor information through HMMs can improve our understanding of both post-release and natural behavior, especially in species that are difficult to observe directly.

Animals across taxa have shown behaviors linked to moon phase (or the proxy of lunar illumination), and marine organisms are well-documented to calibrate certain activities with the moon. Few studies have looked at a possible connection between moon phase and shark attacks on humans, and the results have been preliminary or lacking relationships. We used nearly 50 years of shark attack data from across the globe to test for a relationship between shark attacks and moon phase. We examined factors of geography, shark species, and outcome of attack. From 12 relationships that we tested (totaling 120 comparisons), we found 12 significant outcomes, of which five were positive (i.e., more attacks than expected) and seven were negative (i.e., fewer attacks than expected). Specifically, all the instances of more shark attacks than expected occurred at lunar illumination >50%, while all the instances of fewer shark attacks than expected occurred at lunar illumination of

The mechanisms underlying polyandry and female mate choice in certain taxonomic groups remain widely debated. In elasmobranchs, several species have shown varying rates of polyandry based on genetic studies of multiple paternity (MP). We investigated MP in the finetooth shark, Carcharhinus isodon, in order to directly test the encounter rate hypothesis (ERH), which predicts that MP is a result of the frequency of encounters between mature conspecifics during the breeding season, and should therefore increase when more time is available for copulation and sperm storage. Female finetooth sharks in the northern Gulf of Mexico (GoM) have been found to reproduce with both annual periodicity and biennial periodicity, while finetooth sharks from the northwestern Atlantic Ocean have only been found to reproduce biennially, allowing us to compare mating opportunity to frequency of MP. Our results show high rates of MP with no significant difference in frequency between females in the GoM (83.0%) and Atlantic (88.2%, p =.8718) and varying but nonsignificant rates of MP between females in the GoM reproducing annually (93.0%) and biennially (76.6%, p =.2760). While the ERH is not supported by this study, it remains possible that reproductive periodicity and other physiological factors play a role in determining rates of MP in elasmobranchs, with potential benefits to individuals and populations. [ABSTRACT FROM AUTHOR]

As ecotourists become increasingly interested in snorkeling and diving with sharks, it is important to establish directives for safe interactions. The study considered eye contact between humans and approaching sharks, examining specifically whether an interruption in it owing to, for example, a person glancing at a camera or regarding where to retreat, would affect a shark's behavior. In standardized field tests, divers maintained or interrupted eye contact with approaching Caribbean reef sharks, Carcharhinus perezi. The results showed a significant difference in the sharks' approaches depending on whether the divers maintained or interrupted eye contact with them. More specifically, the analysis revealed that sharks came significantly closer to the divers when eye contact was interrupted and also reduced their speed. [ABSTRACT FROM AUTHOR]

Many large coastal sharks are vulnerable to population declines, however, conflict with human activities often results in unselective culls. Successfully and non-destructively, addressing human-wildlife conflicts requires understanding of animal behavior. However, knowledge about white shark (Carcharodon carcharias) behavior near surf zones, where shark bites usually occur, is still limited. We used drones to obtain high-resolution tracks of 108 white sharks directly off coastal beaches on the east coast of Australia. White sharks ranged from 1.9 to 4.0 m (total length) and typically swam parallel to the beach line at an average speed of 0.82 m s−1 (∼3.0 km h−1), with behavior being characteristic of energy conserving motion and foraging. Notably the presence of schools of fish increased mean swim speeds of sharks by 0.33 m s−1 and caused tracks to be more convoluted. White sharks were also observed to swim straighter and faster with time either side of midday, increasing predicted mean swim speeds by 0.11 m s−1, and net travel velocities by 0.25 m s−1. White sharks also displayed inquisitive behavior toward various potential food and non-food items. We demonstrate that white sharks display largely predictable track trajectories and slow movement speeds along coastal beaches, which has utility in further developing non-destructive shark mitigation strategies. Whilst some of the behavior observed might support the exploratory bite hypothesis, there is likely an increased risk of a shark bite to bathers during situations where there are large shark-attracting food sources present.

In recent years, much attention has been focused on the impact of climate change, particularly via ocean acidification (OA), on marine organisms. Studying the impact of OA on long-living organisms, such as sharks, is especially challenging. When the ocean waters absorb anthropogenic carbon dioxide (CO2), slow-growing shark species with long generation times may be subjected to stress, leading to a decrease in functionality. Our goal was to examine the behavioral and physiological responses of sharks to OA and the possible impacts on their fitness and resilience. We conducted a systematic review in line with PRISMA-Analyses, of previously reported scientific experiments. We found that most studies used CO2 partial pressures (pCO2) that reflect representative concentration pathways for the year 2100 (e.g., pH ~7.8, pCO2 ~1000 μatm). Since there is a considerable knowledge gap on the effect of OA on sharks, we utilized existing data on bony fish to synthesize the available knowledge. Given the similarities between the behaviors and physiology of these two superclasses’ to changes in CO2 and pH levels, there is merit in including the available information on bony fish as well. Several studies indicated a decrease in shark fitness in relation to increased OA and CO2 levels. However, the decrease was species-specific and influenced by the intensity of the change in atmospheric CO2 concentration and other anthropogenic and environmental factors (e.g., fishing, temperature). Most studies involved only limited exposure to future environmental conditions and were conducted on benthic shark species studied in the laboratory rather than on apex predator species. While knowledge gaps exist, and more research is required, we conclude that anthropogenic factors are likely contributing to shark species’ vulnerability worldwide. However, the impact of OA on the long-term stability of shark populations is not unequivocal.

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On rare occasions, during mating season among sharks, 'mating scars' appear on female sharks' bodies caused by the males holding onto them. The low frequency of sharks bearing such scars indicates that those markers are not part of regular mating efforts. These scars are mostly deeper cuts and punctures, indicating a more forceful motivation such as coercive mating from the male's side. We discuss scenarios based on mating scars from three Carcharhinid species, describe and explain the arrangement of these bite scars, and consider plausible mating strategies used by males, including coercive mating. [ABSTRACT FROM AUTHOR]

Abstract The study of the feeding ecology of marine predators is crucial to understanding their ecological roles and advancing our knowledge of marine ecosystem functioning, especially in highly human-impacted areas. Here, we examined the trophic ecology of three abundant demersal sharks, the velvet belly lantern shark Etmopterus spinax , the blackmouth catshark Galeus melastomus and the small-spotted catshark Scyliorhinus canicula , and the rare kitefin shark Dalatias licha of the western Mediterranean Sea. Data were obtained from two deep-water areas with different degrees of human impact: a fishery restricted area (FRA) in the Gulf of Lions and a highly human-impacted area in the Catalan Sea (non-FRA). We combined analyses of individual stomach contents and stable isotope values from different individuals of each shark species. Our results revealed that D. licha is a predator located higher up on the food web, while G. melastomus , E. spinax and S. canicula are located in lower trophic positions. These results confirm that shark species play important and, most likely, complementary roles as predators in the western Mediterranean Sea. Results also revealed that despite some differences in the diet of the shark species, as revealed by the stomach contents, in the long term (isotopic results) the four species showed similar diet habits and similar trophic relationships in both FRA and non-FRA. This may be due to the fact that despite the fishing regulations in the FRA area, the population of the prey species probably do not vary between the two areas. Overall, this study provides new insights into the trophic ecology of these sharks and contributes to an understanding of their ecological roles within the community. Highlights • Diet of four sharks was studied in two different fishing-impact Mediterranean areas. • D. licha is a predator located higher up on the food web. • G. melastomus , E. spinax and S. canicula are located in lower trophic positions. • Diet and trophic relationships of the four sharks is similar between the two areas. [ABSTRACT FROM AUTHOR]

Shark depredation, where a shark partially or completely consumes an animal caught by fishing gear before it can be retrieved to the fishing vessel, occurs in commercial and recreational fisheries worldwide, causing a range of negative biological and economic impacts. Despite this, it remains relatively understudied compared to other fisheries issues. This is the first review of the literature relating to shark depredation, which also includes an overview of the potential mechanisms underlying its occurrence and options for mitigation. Furthermore, this review highlights key research gaps that remain to be investigated, thereby providing impetus for future research. In total, 61 studies have been published between 1955 and 2018, which include information on shark depredation. These studies recorded quantitative rates of depredation between 0.9 and 26% in commercial and recreational fisheries and during research fishing, identified 27 shark species from seven families that were responsible for depredation and discussed potential factors influencing its occurrence. Information from research into bycatch mitigation and the testing of shark deterrent approaches and technologies is also presented, in the context of applying these approaches to the reduction of shark depredation. This review presents an holistic overview of shark depredation in fisheries globally and, in doing so, provides a central resource for fisheries researchers and managers focusing on this topic to stimulate further collaborative research on this important fisheries issue. [ABSTRACT FROM AUTHOR]

Highlights • Respiration of angelshark is characterized by the lack of oropharyngeal motion. • It distinguishes respiration in angelsharks from buccal pumping of benthic fishes. • Angelshark may use gill flaps to pump the respiratory water current over its gills. • This mechanism may increase crypsis in benthic lifestyle. Abstract For benthic fishes, breathing motion (e.g., oral, pharyngeal, and branchial movements) can result in detection by both prey and predators. Here we investigate the respiratory behavior of the angelshark Squatina japonica (Pisces: Squatiniformes: Squatinidae) to reveal how benthic elasmobranchs minimize this risk of detection. Sonographic analyses showed that the angelshark does not utilize water-pumping in the oropharyngeal cavity during respiration. This behavior is in contrast with most benthic fishes, which use the rhythmical expansion/contraction of the oropharyngeal cavity as the main pump to generate the respiratory water current. In the angelshark, breathing motion is restricted to the gill flaps located on the ventral side of the body. We suspect that the gill flaps function as an active pump to eject water through the gill slits. This respiratory mode allows conspicuous breathing motion to be concealed under the body, thereby increasing crypsis capacity. [ABSTRACT FROM AUTHOR]

Abstract The impact of seismic surveys on the catchability of marine fish is a contentious issue, with some claims that seismic surveys may negatively affect catch rates. However little empirical evidence exists to quantify the impacts or identify the mechanisms of such impact. In this study, we used a 2-D seismic survey in the Gippsland Basin, Bass Strait, Australia in April 2015 as an opportunity to quantify fish behaviour (field-based) and commercial fisheries catch (desktop study) across the region before and after airgun operations. Three species found in abundance (gummy shark, swell shark, tiger flathead) were acoustically tagged and released within one of two acoustic arrays (experimental and control zone) and monitored before, during and after the seismic survey. In the field study, only 35% of the gummy sharks and 30% of the swell sharks were subsequently detected two days after release, suggesting movement outside the study area. Various tagged individuals returned sporadically over the monitoring period, including during the seismic survey operations. Behaviour consistent with a possible response to the seismic survey operations was observed for flathead which increased their swimming speed during the seismic survey period and changed their diel movement patterns after the survey. We also investigated the potential impacts of the seismic survey on catch rates using Commonwealth fisheries logbook data from Jan 2012–Oct 2015. Fifteen species and two gear types (Danish seine, gillnet) were modelled to examine differences in catch rates before and after the seismic survey. The catch rates in the six months following the seismic survey were significantly different than predicted in nine out of the 15 species examined, with six species (tiger flathead, goatfish, elephantfish, boarfish, broadnose shark and school shark) showing increases in catch following the seismic survey, and three species (gummy shark, red gurnard, and sawshark) showing reductions. With the exception of flathead movement, we found little evidence for consistent behavioural or catch rate changes induced by the seismic survey in the targeted species, although behavioural data were limited because many sharks left the acoustic receiver array prior to the commencement of the seismic survey. Highlights • We compared acoustic telemetry and fisheries data to a 2015 seismic survey in the Bass Strait. • Many sharks left the area soon after release, but several returned during seismic operations. • Tiger flathead increased swimming speed during the seismic survey period. • Commercial catch rates following the seismic survey were higher in 6 species and lower in 3 species. • There was little evidence of consistent behavioural or catch rate change due to the seismic survey. [ABSTRACT FROM AUTHOR]

A preliminary experience to study, on a small scale, the movements of the young of the year (YOY) Sphyrna lewini (Griffith & Smith, 1834), in the Mexican Central Pacific, using acoustic telemetry within a nursery area. From October to December 2014 seven sharks were tagged with ultrasonic transmitters and tracked for 68 days within a 14 km2 area associated to a river mouth. The quick shark handling allowed their release in less than two minutes and excellent health condition. Although recaptured sharks up to 105 days after tagging did not show symptoms of scar infection, a slight abrasion in the shark skin was observed after 51 days. The ultrasonic transmitter retention was 75%, and the site fidelity was complete (F = 1) during the first ninety days. For the 135-day period, fidelity was 0.63 (0.40-0.80), and the estimated attrition rate was 0.73 (0.34-1). Ninety-seven percent of detections occurred on soft bottoms and less than 30 m depth. The YOY S. lewini stayed active 24 h a day and performed estimated movements of 11.96 km during that time. The home range for all tagged sharks was estimated to be 4.82 km2 using the minimum convex polygon method (MCP) and 4.89 km2 using the kernel utilization distribution method (95% KUD). The KUD estimation showed two core areas within the study area, is the one located in front of the river mouth the most used. [ABSTRACT FROM AUTHOR]

The smooth hammerhead shark, Sphyrna zygaena, is a cosmopolitan semipelagic shark captured as bycatch in pelagic oceanic fisheries, especially pelagic longlines targeting swordfish and/or tunas. From 2012 to 2016, eight smooth hammerheads were tagged with Pop-up Satellite Archival Tags in the inter-tropical region of the Northeast Atlantic Ocean, with successful transmissions received from seven tags (total of 319 tracking days). Results confirmed the smooth hammerhead is a highly mobile species, as the longest migration ever documented for this species (> 6600 km) was recorded. An absence of a diel vertical movement behavior was noted, with the sharks spending most of their time at surface waters (0–50 m) above 23°C. The operating depth of the pelagic longline gear was measured with Minilog Temperature and Depth Recorders, and the overlap with the species vertical distribution was calculated. The overlap is taking place mainly during the night and is higher for juveniles (~40% of overlap time). The novel information presented can now be used to contribute to the provision of sustainable management tools and serve as input for Ecological Risk Assessments for smooth hammerheads caught in Atlantic pelagic longline fisheries. [ABSTRACT FROM AUTHOR]

Spatial separation within predator communities can arise via territoriality but also from competitive interactions among and within species. However, linking competitive interactions to predator distribution patterns is difficult and theoretical models predict different habitat selection patterns dependent on habitat quality and how competition manifests itself. While models generally consider competitors to be either equal in ability, or for one phenotype to have a fixed advantage over the other, few studies consider that an animal may only have a competitive advantage in specific habitats. We used  10 years of telemetry data, habitat surveys and behavioral experiments, to show spatial partitioning between and within two species of reef shark (grey reef Carcharhinus amblyrhinchos and blacktip reef sharks C. melanopterus) at an unfished Pacific atoll. Within a species, sharks remained within small ‘sub‐habitats’ with very few movements of individuals between sub‐habitats, which previous models have suggested could be caused by intra‐specific competition. Blacktip reef sharks were more broadly distributed across habitat types but a greater proportion used lagoon and backreef habitats, while grey reef sharks preferred forereef habitats. Grey reef sharks at a nearby atoll where blacktip reef sharks are absent, were distributed more broadly between habitat types than when both species were present. A series of individual‐based models predict that habitat separation would only arise if there are competitive interactions between species that are habitat‐specific, with grey reefs having a competitive advantage on the forereefs and blacktips in the lagoons and backreef. We provide compelling evidence that competition helps drive distribution patterns and spatial separation of a marine predator community, and highlight that competitive advantages may not be constant but rather dependent on habitats. [ABSTRACT FROM AUTHOR]

Knowing how often animals engage in different behaviors and their energetic costs may explain why animals behave the way they do in the wild. This study sought to investigate the relationship between the frequency of various swimming behaviors and their associated energetic costs (oxygen consumption rates) in situ for juvenile lemon sharks (Negaprion brevirostris). Behaviors were identified for captive animals and remotely observed for animals in the wild with accelerometers, and oxygen consumption rates of behaviors were estimated using acceleration-calibrated relationships. Lemon sharks rested infrequently (4.3% of deployment), and the occurrence of active swimming behaviors was inversely related to their respective oxygen consumption rates. Furthermore, time of day and tide state influenced when lemon sharks exhibited active swimming behaviors - but not resting - such that sharks were most active during the day on flooding tides. Oxygen consumption rates also differed across and within different behaviors with time of day and tide state, although mean oxygen consumption rates were highest on daytime flooding tides and uniformly reduced across all other diel and tide combinations. Despite variation in oxygen consumption rates, however, lemon shark activity occurred at 32.3-35.6% of their aerobic metabolic scope. These data do not provide a clear oxygen consumption basis for swimming behaviors observed in situ, which may have been masked by potentially stronger ecological drivers (e.g., predator-prey dynamics). However, these data are relevant to linking behavioral modifications to changes in energy use that shows much promise for addressing conservation issues in fishes. [ABSTRACT FROM AUTHOR]

Cookie-cutter sharks (Isistius sp.) are small squaloid sharks that live in tropical and sub-tropical oceans. Their name comes from their unique tactic of feeding, which enables them to parasitize marine mega-fauna, like cetaceans. Due to their morphological and anatomical characteristics, they are responsible of crater-like wounds on the skin of marine mammals. Little is known on Isistius sp. around the globe especially in Martinique, which represents a potential habitat. The main goal of this study was to assess the impact of cookie-cutter sharks on cetaceans by determining (1) seasonal changes in the occurrence of bites, (2) intra- and interspecific differences in frequencies and locations of bites among the different species of cetaceans, and (3) link behavior patterns of both cookie-cutter sharks and cetaceans. Data were collected from a 3-year photo-identification database of Cetaceans in Caribbean coast of Martinique. 431 wounds of various stages on 396 individuals from nine species of marine mammals were recorded. Results did not show any significant variation in the occurrence of wounds between seasons. Intermediate state was more important, most injuries were observed on the SCF (Superior Central Flank) (62.40%) and in a lesser extent on young individuals (3.25%). The predation of cookie-cutter sharks on different cetacean species has been confirmed consistently in Martinique. Further studies are required with both scientists and fishermen to better understand their specific role in this marine ecosystem. [ABSTRACT FROM AUTHOR]

When conducting biological investigations on shark species, capture and brief restraint procedures may be required in order to collect ecological, behavioral and physiological data. Tonic immobility is an innate, reversible, coma-like stasis displayed by a large number of taxa, including sharks, and has been used for brief restraint, but is rarely used during capture itself. Here, we present a novel, non-lethal capture method of zebra sharks, Stegostoma fasciatum, using tonic immobility, in the field. Zebra sharks were caught by free diving, and on SCUBA, inducing a state of tonic immobility by quickly applying tight-fisted manual pressure to the caudal fin, instead of the dorso-ventral inversion method. Divers were then able to collect tissue samples for genetic analysis, and in some cases, maintain the animals in a state of tonic immobility during transport up to the research vessel for additional data collection. Decreased duration of anthropogenic intervention, and minimal physical struggle associated with this capture and restraint method is expected to reduce physiological markers of distress. Tonic immobility induction and other methods of non-lethal capture deserve continued investigation. [ABSTRACT FROM AUTHOR]

Abstract: This article reports on the first comparative surveys in two separate locations to measure public attitudes toward sharks following shark bite incidents. This study focuses directly on the communities affected by the shark bites, both in Australia—the town of Ballina in the State of New South Wales (N = 500) and the city of Perth in Western Australia (N = 600)—and reports on their attitudes and policy preferences relating to sharks immediately after serious shark bite incidents in 2015 and 2016. In both communities we find that a large majority of respondents prefer nonlethal policies; most respondents believe shark bite incidents to be accidental rather than intentional; while fear of sharks correlates with support for lethal policies, this association is powerfully mediated by perceptions of intentionality. These findings have implications for international wildlife management, particularly regarding predator species in need of conservation. Conservation is based on the public acceptability of a species and if intentionality can mediate fear effects and promote policies that protect the species this is a step forward for conservation management globally. [ABSTRACT FROM AUTHOR]

The blue shark (Prionace glauca) and the shortfin mako shark (Isurus oxyrinchus) are two large and highly migratory sharks distributed in most oceans. Although they are often caught in the south Pacific Ocean long-line fisheries, their trophic ecology is poorly understood. Stable isotopes with Bayesian mixing and dependence concentration models were performed to determine the diet and trophic differences between the two species in the South-eastern Pacific Ocean. According to the mixing models, fishes are the most important prey of these sharks. Dolphin calves and remains were found in the stomachs of both species, which represents a novel finding in trophic ecology of South Pacific sharks. Intra-specific differences were found inP. glauca, but not in specimens ofI. oxyrinchus. The two sharks showed a high degree of diet overlap (73%), primarily over mackerel and dolphin carcasses. Our results indicate that blue and shortfin mako sharks have a generalist feeding strategy in the eastern Pacific Ocean, with a strong preference for teleost fishes and also for dolphin carcasses. Therefore, trophic studies are useful to understand energy flow through the food web, and the trophic position of key species. [ABSTRACT FROM PUBLISHER]

This article reports on new research that finds certain messages reduce fear of sharks, key to promoting conservation-minded responses to shark bites. Here it is argued that the sophistication in public feelings toward these highly emotional events has allowed new actors to mobilize and given rise to the ‘Save the Sharks’ movement. In a unique experiment coupling randomly assigned intent-based priming messages with exposure to sharks in a ‘shark tunnel’, a potential path to reduce public fear of sharks and alter policy preferences is investigated. Priming for the absence of intent yielded significant fear extinction effects, providing a viable means of increasing support for non-lethal policy options following shark bite incidents. High levels of pride and low levels of blame for bite incidents are also found. In all, this article provides a step towards improving our understanding of fear and fear reduction in public policy. [ABSTRACT FROM AUTHOR]

Sensory systems play a central role in guiding animal behaviour. They can be manipulated to alter behavioural outcomes to limit negative interactions between humans and animals. Sharks are often seen as a threat to humans and there has been increasing interest in developing shark mitigation devices. Previous research has concentrated on stimulating the electrosensory and olfactory systems of sharks, whereas the influence of light and sound on their behaviour has received little attention. In this study, the effects of an intense strobe light and a loud, artificial sound composed of mixed frequencies and intensities on shark behaviour were assessed. We tested these stimuli individually and in combination on wild-caught captive Port Jackson ( Heterodontus portusjacksoni) and epaulette ( Hemiscyllium ocellatum) sharks in aquaria and on wild great white sharks ( Carcharodon carcharias) in the field. When presented alone and in combination with sound, the lights reduced the number of times that the bait was taken by both H. portusjacksoni and H. ocellatum in captivity. The strobe light alone, however, did not affect the behaviour of white sharks, but when presented in combination with sound, white sharks spent significantly less time in proximity to the bait. As the lights and sound presented in this study did not show a pronounced deterrent effect on C. carcharias, we do not advise their use as a strategy for mitigating shark-human interactions. However, due to the potential effectiveness of strobe lights in deterring other species of sharks, there may be applications for this approach in the reduction of fisheries bycatch. [ABSTRACT FROM AUTHOR]

Quantifying the behavioural response of chondrichthyans to capture in longline fisheries can assist in understanding the physiological changes resulting from capture stress and ultimately aid in developing fishing practices that increase the survival of released bycatch species. Here, we evaluated the use of time-depth recorders (TDR) as a tool to quantify the amount of movement during capture across 42 animals from seven species of shark and one species of ray caught on hooks with TDRs attached in either a demersal or surface longline. Depth changes over time were analysed using three methods to estimate the percentage of time sharks and rays struggled on the line. Methods used were; 1) a Visual Assessment Method (VAM) of the TDR trace conducted by two investigators quantifying movement by summing the duration of movement bouts visually identified by erratic changes of depth; 2) the Gangion Extension Method (GEM) which quantifies movement by summing periods when captured animals altered their depth by > 50% of the gangion length; and 3) the Vertical Excursion Method (VEM) which quantifies movement by summing periods when the absolute depth change between successive data points exceeded a threshold determined from the maximum depth change in the TDR data prior to capture of the animal. We found that the VAM was consistent across investigators and produced significantly higher estimates of movement than GEM and VEM. Estimates of movement from GEM and VEM were not significantly different to each other, but unlike GEM, VEM could be applied to TDRs used in both surface and demersal longlines. The amount of movement observed was different between species and such differences were consistent across all methods, indicating that species-specific behavioural responses to capture can be identified. The ability to assess capture behaviour using VEM allows inter-species comparisons, which may be used as a metric for rapid, generalised assessment of species' responses to longline capture where physiological data may be limited or lacking. Such assessments are important in the design of species-specific management for bycaught animals. [ABSTRACT FROM AUTHOR]

The bluntnose sixgill shark ( Hexanchus griseus Bonnaterre 1788) is a large, deepwater apex predator that, in a few unique locations such as the Strait of Georgia, Canada, occupies shallow, inshore waters as juveniles. The occurrence of pregnant females in the Strait of Georgia suggests that this is an important area for parturition and juvenile rearing. Bluntnose sixgill sharks are listed under the Canadian Species at Risk Act, and an understanding of their behaviour in habitat selection during important life stages is an important component for conservation measures. We employed satellite tags to identify the daily and seasonal depth and thermal habitats of juvenile bluntnose sixgill sharks in the Strait of Georgia. Tag release and depth information suggests that juvenile bluntnose sixgill sharks within the Strait of Georgia remain there until they mature and migrate to offshore deepwaters. The dominant depth habitat utilized by the juvenile sharks in our study was deepwater (>200 m), with only occasional occupation of depths <100 m, indicating that even within coastal areas, juveniles still prefer deepwater. Overall the sharks occupied shallower depths at night than during the day with increased vertical activity in both the day and night compared to crepuscular periods. Seasonally, the sharks occupied shallower depths in the summer than in winter, but inconsistency in the temperatures with which those depths were associated suggests that their vertical behaviour is influenced by local foraging opportunities and not by thermoregulation. [ABSTRACT FROM AUTHOR]

This research examines a series of six Florida forensic anthropology cases that exhibit taphonomic evidence of marine deposition and shark-feeding activities. In each case, we analyzed patterns of trauma/damage on the skeletal remains (e.g., sharp-force bone gouges and punctures) and possible mechanisms by which they were inflicted during shark predation/scavenging. In some cases, shark teeth were embedded in the remains; in the absence of this evidence, we measured interdental distance from defects in the bone to estimate shark body length, as well as to draw inferences about the potential species responsible. We discuss similarities and differences among the cases and make comparisons to literature documenting diagnostic shark-inflicted damage to human remains from nearby regions. We find that the majority of cases potentially involve bull or tiger sharks scavenging the remains of previously deceased, adult male individuals. This scavenging results in a distinctive taphonomic signature including incised gouges in cortical bone. [ABSTRACT FROM AUTHOR]

Suction feeding in teleost fish is a power-dependent behavior, requiring rapid and forceful expansion of the orobranchial cavity by the hypobranchial and trunk muscles. To increase power production for expansion, many species employ in-series tendons and catch mechanisms to store and release elastic strain energy. Suction feeding sharks such as Chiloscyllium plagiosum lack large in-series tendons on the hypobranchials, yet two of the hypobranchials, the coracohyoideus and coracoarcualis (CH and CA; hyoid depressors), are arranged in-series, and run deep and parallel to a third muscle, the coracomandibularis (CM, jaw depressor). The arrangement of the CH and CA suggests that C. plagiosum is using the CH muscle rather than a tendon to store and release elastic strain energy. Here we describe the anatomy of the feeding apparatus, and present data on hyoid and jaw kinematics and fascicle shortening in the CM, CH and CA quantified using sonomicrometry, with muscle activity and buccal pressure recorded simultaneously. Results from prey capture show that prior to jawand hyoid depression the CH is actively lengthened by shortening of the in-series CA. The active lengthening of the CH and pre-activation of the CH and CA suggest that the CH is functioning to store and release elastic energy during prey capture. Catch mechanisms are proposed involving a dynamic moment arm and four-bar linkage between the hyoidiomandibular ligament (LHML), jaws and ceratohyals that is influenced by the CM. Furthermore, the LHML may be temporarily disengaged during behaviors such as bite processing to release linkage constraints. [ABSTRACT FROM AUTHOR]

Knowledge of the diel spatial ecology of wild animals is of great interest to ecologists and relevant to resource management and conservation. Sharks are generally considered to be more active during nocturnal periods than during the day; however, few studies have empirically evaluated diel variation in shark habitat use and how anthropogenic disturbances may influence these patterns. In the western central Atlantic Ocean, tiger sharks ( Galeocerdo cuvier ) are highly abundant in the shallow waters of the Little Bahama Bank, Bahamas. Within the northwest edge of the Bank, there is an area nicknamed “Tiger Beach,” where tiger sharks are provisioned year-round at spatially discrete ecotourism dive sites spanning ~ 1.5 km 2 . In this study, we used an array of acoustic receivers encircling an area of 102.4 km 2 to evaluate for potential differences in diel spatial habitat use patterns for 42 tagged tiger sharks at Tiger Beach and the surrounding area. Using tracking data from 24 June 2014 to 13 May 2015, we evaluated spatial and diel patterns of shark activity space, centers of activity, residency and the daily proportion of sharks detected within the array. Sharks were detected during both day and night with no significant diel differences in habitat use metrics across the array, although spatial differences in residency existed. Four sharks accounted for 53.8% of residency data throughout the tracking period, with the majority of sharks primarily entering and exiting the array, except during summer months when the most of the tagged tiger sharks were absent from the array. We also found limited empirical support for hypothesized effects of provisioning tourism on tiger shark habitat use. However, additional research at finer, individual scales, may be needed to better resolve the potential influence of provisioning on tiger sharks at Tiger Beach. [ABSTRACT FROM AUTHOR]

Positioned at the intersection of the head, body and forelimb, the pectoral girdle has the potential to function in both feeding and locomotor behaviours-although the latter has been studied far more. In ray-finned fishes, the pectoral girdle attaches directly to the skull and is retracted during suction feeding, enabling the ventral body muscles to power rapid mouth expansion. However, in sharks, the pectoral girdle is displaced caudally and entirely separate from the skull (as in tetrapods), raising the question of whether it is mobile during suction feeding and contributing to suction expansion. We measured three-dimensional kinematics of the pectoral girdle in white-spotted bamboo sharks during suction feeding with X-ray reconstruction of moving morphology, and found the pectoral girdle consistently retracted about 118 by rotating caudoventrally about the dorsal scapular processes. This motion occurred mostly after peak gape, so it likely contributed more to accelerating captured prey through the oral cavity and pharynx, than to prey capture as in ray-finned fishes. Our results emphasize the multiple roles of the pectoral girdle in feeding and locomotion, both of which should be considered in studying the functional and evolutionary morphology of this structure. [ABSTRACT FROM AUTHOR]

Knowledge of the diet and trophic ecology of apex predators is key for the implementation of effective ecosystem as well as species-based management initiatives. Using a combination of stomach content data and stable isotope analysis (δ15N and δ13C) the current study provides information on size-based and sex-specific variations in diet, trophic position (TP) and foraging habitat of tiger sharks (Galeocerdo cuvier) caught in the KwaZulu-Natal Sharks Board bather protection program. This study presents the longest time-series and most detailed analysis of stomach content data for G. cuvier worldwide. Prey identified from 628 non-empty stomachs revealed a size-based shift in diet. Reptiles, birds, mysticetes, and large shark species increased in dietary importance with G. cuvier size, concomitant with a decrease in smaller prey such as batoids and teleosts. Seasonal and decadal shifts in diet driven primarily by changes in the importance of elasmobranchs and mammal (cetacean) prey were recorded for medium sized (150–220 cm) G. cuvier. Both stomach content and stable isotope analysis indicated that G. cuvier is a generalist feeder at the population level. Size-based δ13C profiles indicated a movement to offshore foraging habitats by larger G. cuvier. Calculated TP varied by method ranging from 4.0 to 5.0 (TPSCA for stomach contents) and from 3.6 to 4.5 (TPscaled and TPadditive for δ15N). Large (> 220 cm) G. cuvier did not feed at discrete trophic levels, but rather throughout the food web. These data provide key information on the ecological role of G. cuvier to improve the accuracy of regional food web modelling. This will enable a better understanding of the ecological impacts related to changes in the abundance of this predator. [ABSTRACT FROM AUTHOR]

Lamniform sharks are apex marine predators undergoing dramatic local and regional decline worldwide, with consequences for marine ecosystems that are difficult to predict. Through their long history, lamniform sharks have faced widespread extinction, and understanding those ‘natural experiments’ may help constrain predictions, placing the current crisis in evolutionary context. Here we show, using novel morphometric analyses of fossil shark teeth, that the end-Cretaceous extinction of many sharks had major ecological consequences. Post-extinction ecosystems supported lower diversity and disparity of lamniforms, and were dominated by significantly smaller sharks with slimmer, smoother and less robust teeth. Tooth shape is intimately associated with ecology, feeding and prey type, and by integrating data from extant sharks we show that latest Cretaceous sharks occupied similar niches to modern lamniforms, implying similar ecosystem structure and function. By comparison, species in the depauperate post-extinction community occupied niches most similar to those of juvenile sand tigers (Carcharias taurus). Our data show that quantitative tooth morphometrics can distinguish lamniform sharks due to dietary differences, providing critical insights into ecological consequences of past extinction episodes. [ABSTRACT FROM AUTHOR]

We have developed a population dynamics model that considers the spatial segregation by sex and ontogenetic stages of pelagic sharks. The model was used to evaluate the performance of harvest strategies based on ecological characteristics. We proposed five harvest strategies for longline fisheries based on the ecological characteristics of blue shark ( Prionace glauca) in the North Pacific. Management objectives for depleted populations are to increase yield to the level that provides maximum sustainable yield through increases in biomass without collapsing the fishery. Deterministic and stochastic analyses were undertaken. We determined that the harvest of male sharks was robust to uncertainty of environmental changes, reducing the likelihood of fishery collapse and stabilizing yield and mean biomass. The harvest of male sharks was also robust to the uncertainties of biological parameters such as natural mortality and steepness. These results suggested that if there was no sperm limitation or impact on the mating behavior of the species, the harvest of males would be the most appropriate harvest strategy for blue shark in the North Pacific. [ABSTRACT FROM AUTHOR]

Food web structure is shaped by interactions within and across trophic levels. As such, understanding how the presence and absence of predators, prey, and competitors affect species foraging patterns is important for predicting the consequences of changes in species abundances, distributions, and behaviors. Here, we used plasma δ 13 C and δ 15 N values from juvenile blacktip reef sharks ( Carcharhinus melanopterus ) and juvenile sicklefin lemon sharks ( Negaprion acutidens ) to investigate how species co-occurrence affects their trophic interactions in littoral waters of Moorea, French Polynesia. Co-occurrence led to isotopic niche partitioning among sharks within nurseries, with significant increases in δ 15 N values among sicklefin lemon sharks, and significant decreases in δ 15 N among blacktip reef sharks. Niche segregation likely promotes coexistence of these two predators during early years of growth and development, but data do not suggest coexistence affects life history traits, such as body size, body condition, and ontogenetic niche shifts. Plasticity in trophic niches among juvenile blacktip reef sharks and sicklefin lemon sharks also suggests these predators are able to account for changes in community structure, resource availability, and intra-guild competition, and may fill similar functional roles in the absence of the other species, which is important as environmental change and human impacts persist in coral reef ecosystems. [ABSTRACT FROM AUTHOR]

We investigated drivers of reef shark demography across a large and isolated marine protected area, the British Indian Ocean Territory Marine Reserve, using stereo baited remote underwater video systems. We modelled shark abundance against biotic and abiotic variables at 35 sites across the reserve and found that the biomass of low trophic order fish (specifically planktivores) had the greatest effect on shark abundance, although models also included habitat variables (depth, coral cover and site type). There was significant variation in the composition of the shark assemblage at different atolls within the reserve. In particular, the deepest habitat sampled (a seamount at 70-80m visited for the first time in this study) recorded large numbers of scalloped hammerhead sharks (Sphyrna lewini) not observed elsewhere. Size structure of the most abundant and common species, grey reef sharks (Carcharhinus amblyrhynchos), varied with location. Individuals at an isolated bank were 30% smaller than those at the main atolls, with size structure significantly biased towards the size range for young of year (YOY). The 18 individuals judged to be YOY represented the offspring of between four and six females, so, whilst inconclusive, these data suggest the possible use of a common pupping site by grey reef sharks. The importance of low trophic order fish biomass (i.e. potential prey) in predicting spatial variation in shark abundance is consistent with other studies both in marine and terrestrial systems which suggest that prey availability may be a more important predictor of predator distribution than habitat suitability. This result supports the need for ecosystem level rather than species-specific conservation measures to support shark recovery. The observed spatial partitioning amongst sites for species and life-stages also implies the need to include a diversity of habitats and reef types within a protected area for adequate protection of reef-associated shark assemblages. [ABSTRACT FROM AUTHOR]