Hammerhead Sharks Research Articles

Corrigendum: Renewed occurrence of schooling scalloped hammerhead (Sphyrna lewini) and of great hammerhead (S. mokarran) sharks in the Cayman Islands

Corrigendum: Renewed occurrence of schooling scalloped hammerhead (Sphyrna lewini) and of great hammerhead (S. mokarran) sharks in the Cayman Islands

First Data on Anthropogenic Microparticles in the Gastrointestinal Tract of Juvenile Scalloped Hammerhead Sharks (Sphyrna lewini) in the Gulf of California

Scalloped hammerhead sharks (Sphyrna lewini) are critically endangered, according to the International Union for Conservation of Nature Red List, likely due to anthropogenic activities such as intense fishing and pollution. Nowadays, plastic debris contamination is a subject of concern due to its extensive presence in the sea and the digestive tracts of many fish species. The possible effects of plastic debris as a vector of other pollutants are still unknown. We analyzed the digestive tract of 58 hammerhead sharks to investigate the correlation between plastic and other anthropogenic microparticle contamination and their feeding habits in the eastern region of the Gulf of California, revealing a debris contamination occurrence of 79.3%. Out of these, 91.4% corresponded to fibers, and the remaining 8.6% to fragments. The main component of the debris was cellulose (64.4%). According to their diet, these organisms exhibit benthopelagic habits, feeding both in the water column and on the seabed. These results indicate a high level of contamination of anthropogenic cellulosic microfibers in the area. Although cellulosic microfibers are recognized as a biomaterial, they can be harmful to marine species, posing an additional threat to this iconic shark. This changed according to the year, indicating that the anthropogenic microparticle ingestion is related to the discharges of human activities and their seasonality rather than to a selection process by the sharks.

Autonomous Vision-Based Navigation and Stability Augmentation Control of a Biomimetic Robotic Hammerhead Shark

The application potential of robotic fish embedded with intelligent visual navigation algorithms in underwater autonomous operation is on full display recently. However, the existing visual navigation methods are limited by the underwater visual conditions and the motion characteristics of robotic fish. To this end, this paper proposes a novel autonomous navigation framework integrated with visual stabilization control. In practice, a stereo vision-based navigation network is proposed to generate the guidance law. On this basis, a biomimetic robotic hammerhead shark with a controllable cephalofoil is developed, and a nonlinear model predictive controller for cephalofoil stabilization relying on the dynamic model is elaborately designed. Extensive simulations and underwater experiments are conducted to validate the effectiveness and superiority of the proposed methods, which significantly enhance exploration efficiency and reduce image jitter by 26.02% compared to the traditional methods. The obtained results provide a new idea for underwater robots to autonomously explore the ocean. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —This paper is motivated by the problem of vision-based underwater autonomous navigation for a biomimetic robotic fish that possesses underwater visual stability and good maneuverability. The existing visual navigation networks usually generate unexpected navigation instructions when dealing with complex or ambiguous underwater scenes. Additionally, image jitter caused by the rhythmic motion of robotic fish can lead to navigation failure. This paper suggests an integrated navigation framework that includes a biomimetic platform design, a visual stabilization controller, and an intelligent underwater navigation network. Specifically, a novel sphyrnidae-inspired robotic shark is designed as a new platform with superior motion performance. To enhance underwater visual stability, a nonlinear model predictive control-based visual stabilization controller is proposed. Furthermore, a deep stereo attention navigation network based on a parallax attention mechanism is proposed to improve the generalization of vision-based autonomous navigation. A series of underwater search experiments on the robotic shark demonstrate the effectiveness and superiority of the proposed navigation framework. Hopefully, our proposed methods can provide valuable guidance and support for universal underwater robot navigation to accomplish practical marine tasks, such as underwater rescue, resource exploitation, biological observation, and so on.

Fisher’s perceptions on shark fisheries in Sao Tome Island (Gulf of Guinea, West Africa)

Sao Tome and Principe (STP) is a small island developing state in the Gulf of Guinea (West Africa) and is considered a global hotspot of marine biodiversity. Still, detailed information on sharks’ diversity, abundance, and respective fisheries is mainly absent. Here, we interviewed fishers from different local communities of the island of Sao Tome to characterize: i) local knowledge on shark fisheries, ii) those reliant upon these resources, and iii) their perceptions about shark populations and their importance on Sao Tome Island. A total of 111 semi-structured interviews were conducted between May 6 and June 15, 2019, in 11 fishing communities. Ninety-seven percent of fishers mentioned that sharks are present in their fishing grounds, and 98 % reported that they catch sharks. The species most identified by fishers (77 %) was the scalloped hammerhead shark (Sphyrna lewini), followed by the bluntnose sixgill shark (Hexanchus griseus; 33 %), white shark (Carcharodon carcharias; 31 %), longfin mako shark (Isurus paucus; 29 %), pigeye shark (Carcharhinus amboinensis; 27 %), and other six species (under 20 % each). Sixty-two percent of interviewees perceived sharks as a threat to their safety and livelihoods. When asked if sharks should be protected, 59 % of fishers agreed, while 40 % did not consider it necessary. Common reasons in support of protection were that sharks were disappearing (23 %), important for ocean health (9 %), and overfished (5 %). Most fishers (89 %) noticed shark abundance changes, decreasing over the past 15 years. Regarding the underlying causes, the most common response was the increase in the fishing pressure from international fishing fleets (72 %). We argue that raising awareness and building capacity close to local communities on sharks' essential role and importance will be fundamental to supporting future conservation measures, as misinformation and prejudice against sharks are widespread.

Towards Unusual Rolled Swimming Motion of a Bioinspired Robotic Hammerhead Shark Under Negative Buoyancy

Towards Unusual Rolled Swimming Motion of a Bioinspired Robotic Hammerhead Shark Under Negative Buoyancy

Landings of Sphyrna zygaena (Linnaeus, 1758) in northern Peru indicate a lack of adult specimens

A commercial fishery for the smooth hammerhead shark (Sphyrna zygaena) exists in the waters off northern Peru. Although international and domestic norms regulate this species, adult specimens are becoming rare. Monthly visits to four ports in the La Libertad region were made to measure S. zygaena landings and understand the present state of the fishery. We found that 92% of the specimens landed were juveniles or younger and that 10% of the original biomass remains in the fishery. This highlights that stricter regulations such as protecting breeding areas, establishing a legal catch length, and limiting the catch volume and fishing season are urgently needed to maintain a sustainable fishery.

The hammerhead shark's cephalofoil reduces fluid moments during turning motion

The hammerhead shark's cephalofoil reduces fluid moments during turning motion

Genomic population structure of great hammerhead sharks (Sphyrna mokarran) across the Indo-Pacific

Context Currently, little information exists describing the population structure of great hammerhead sharks (Sphyrna mokarran) in Australian waters. Aims This study used single nucleotide polymorphisms to investigate fine-scale population structure in S. mokarran across the Indo-Pacific. Methods DNA was extracted from 235 individuals across six Australian locations and a Red Sea outgroup. Population parameters were calculated and visualised to test structuring across locations. Key results No fine-scale population structuring was observed for S. mokarran across the Indo-Pacific. However, population structuring occurred for all Australian locations when compared to the Red Sea outgroup. Conclusions Findings suggest a single stock is most likely for S. mokarran found in Australian waters. Results provide key information for understanding the broad range movements of S. mokarran and help to define the scale of management required to preserve genetic diversity in this species. The structuring between Australia and the Red Sea indicates limited gene flow and movement. Implications Results indicate that large-scale movements of S. mokarran could be occurring to facilitate genetic mixing. Future research focusing on individual tagging to corroborate movements would be highly beneficial to determine how far (and often) individuals are dispersing, and to note where cross-jurisdictional management, including from neighbouring regions in the Indo-West Pacific–Oceania region, are most critical.

Resource partitioning in hammerhead shark species out-migrating from coastal ecosystems in the Gulf of California

Juveniles of large hammerhead shark species occupy coastal nurseries before migrating offshore to reproduce. In the central Gulf of California, artisanal elasmobranch fisheries have reported catches of juvenile scalloped Sphyrna lewini and smooth S. zygaena hammerhead sharks, but their local foraging habits are yet to be fully understood. In this study, the trophic niches of both hammerhead species as well as of sympatric Pacific sharpnose sharks Rhizoprionodon longurio were investigated using stable isotope values (δ13C, δ34S and δ15N) and fatty acid compositions in whole blood and muscle tissues. Despite interspecific similarities among trophic niches, smooth hammerheads were characterized by lower δ13C, higher δ34S and greater proportion of docosahexaenoic acid (DHA) in both tissues, suggesting they were already partly relying on offshore pelagic resources. For scalloped hammerheads, muscle reflected coastal dietary resources, while offshore trophic markers were detected in blood integrating prey signal over shorter time periods, indicating their more recent initiation of ontogenetic migration. Multidimensional niche calculation revealed low overlap between hammerhead shark trophic niches, implying that potential fine-scale differences in habitat use could reduce competition between these morphologically and ecologically similar species. In the meantime, the isotopic niches of juvenile scalloped and smooth hammerheads were smaller than that of Pacific sharpnose sharks, suggesting they could be more specialized consumers. Overall, the identification of foraging grounds for juvenile hammerhead sharks calls for a future characterization of their residency time in coastal ecosystems to further understand their interactions with fishing pressure in the Gulf of California.

Renewed occurrence of schooling scalloped hammerhead (Sphyrna lewini) and of great hammerhead (S. mokarran) sharks in the Cayman Islands

The scalloped hammerhead shark (Sphyrna lewini), a critically endangered species with a decreasing global population, is characterised by its occurrence in large schools. Such schools are still observed today in the Pacific Ocean, but this is generally not the case in the Atlantic Ocean, and in the Cayman Islands not since the 1970s. Here we report a recent record of a school of S. lewini in deep water off Grand Cayman, and describe a recent, concomitant increase in numbers of the species, and its critically endangered congener, the great hammerhead (Sphyrna mokarran), around the Cayman Islands. Relative population trends and seasonal patterns were assessed using data from shallow and deep-water BRUVS, scientific longlining, citizen science projects including the Sharklogger Network and REEF, and social media reports. It appears that S. lewini may be slowly re-occupying the area, selecting and using deeper waters to school, while S. mokarran has also become less scarce than hitherto.

Fifteen years of elasmobranchs trade unveiled by DNA tools: Lessons for enhanced monitoring and conservation actions

The trade of elasmobranchs (sharks and rays) in Brazil threatens the country's rich endemic biodiversity. The present study explored the use of DNA-based tools to monitor the Brazilian elasmobranch trade, focusing on their role in identifying processed products and supporting conservation efforts. A systematic search of literature was conducted and included 35 peer-reviewed papers published between 2008 and 2023. A shift from the development of DNA-based tools to direct trade applications has been observed since 2015. Molecular identification challenges, including costly sequencing and limited resources in national databases, were identified along with proposed solutions, such as protocol optimization and exploration of cost-effective alternatives. Biases in trade analysis papers, particularly the lack of research in the Northeast Region of Brazil, and issues with sample sizes were evident. Species identified using DNA-based tools included the critically endangered Scalloped Hammerhead Shark (Sphyrna lewini), which appeared in 46 % of the evaluated papers, followed by the Blue Shark (Prionace glauca), and several others threatened species, such as the critically endangered and endemic Brazilian Guitarfish (Pseudobatos horkelii) and the recently categorized as vulnerable Sharpnose Shark (Rhizoprionodon porosus). Other species were reassessed by IUCN, including previously non-threatened species that are now at risk, emphasizing the need for fisheries management, trade monitoring and conservation measures. Our findings highlight the importance of continued genetic monitoring to analyze market trends and adjust legislation, encouraging compliance with frequent inspections to enhance wildlife conservation. We also identified gaps in research and recommended strategies for accurate species identification, broader investigation, and effective management.

Local adaptive variation in a highly migratory fish: The smooth hammerhead shark Sphyrna zygaena

Populations of highly mobile species that undertake long distance migrations are typically considered to be panmictic. Nonetheless, mechanisms related to behavior or local environmental conditions promote genetic isolation in the absence of physical barriers. Highly migratory shark species exhibit varying levels of fidelity to specific regions, shaping the genetic architecture of different populations and resulting in geographically based genetic variation with potential adaptive value. An understanding of the genetic variation of highly migratory species is needed to develop effective conservation strategies. This study aimed to assess the neutral and adaptive variation of the smooth hammerhead shark (Sphyrna zygaena) in the northern Mexican Pacific (NMP) via single nucleotide polymorphisms (SNPs). We analyzed 1480 SNPs in 92 individuals from four geographic regions in the NMP, of which 1469 SNPs were neutral loci (n-SNP), and 11 were putatively under selection (o-SNP) using four genoma scan methods. Genetic diversity was geographically similar among regions (Ho = 0.275). The neutral variation showed panmixia (n-SNPs; FST = 0.0012, p = 0.44), which may be associated with the high dispersal capacity of S. zygaena. A pattern of adaptive variation between individuals from the Gulf of California and Pacific coast was revealed using o-SNPs FST-based methods (24 oSNPs; FST = 0.061, p < 0.001), which may be promoted by individual preferences based on physiological limitations. The estimated effective population size (Ne) of S. zygaena was 1390 individuals, which is theoretically optimal for the population to persist over time.

Depredation rates and spatial overlap between Great Hammerheads and Tarpon in a recreational fishing hot spot

AbstractObjectiveShark depredation, the full or partial consumption of a hooked fish by a shark before it is landed, is an increasing source of human–wildlife conflict in recreational fisheries. Reports of shark depredation in the catch‐and‐release Tarpon (also known as Atlantic Tarpon) Megalops atlanticus fishery in the Florida Keys are increasing, specifically in Bahia Honda, a recreational fishing hot spot and a putative Tarpon prespawning aggregation site.MethodsUsing visual surveys of fishing in Bahia Honda, we quantified depredation rates and drivers of depredation. With acoustic telemetry, we simultaneously tracked 51 Tarpon and 14 Great Hammerheads (also known as Great Hammerhead Sharks) Sphyrna mokarran, the most common shark to depredate Tarpon, to quantify residency and spatial overlap in Bahia Honda.ResultDuring the visual survey, 394 Tarpon were hooked. The combined observed shark depredation and immediate postrelease predation rate was 15.3% for Tarpon that were fought longer than 5 min. Survival analysis and decision trees showed that depredation risk was highest in the first 5–12 min of the fight and on the outgoing current. During the spawning season, Great Hammerheads shifted their space use in Bahia Honda to overlap with Tarpon core use areas. Great Hammerheads restricted their space use on the outgoing current when compared to the incoming current, which could drive increased shark–angler interactions.ConclusionBahia Honda has clear ecological importance for both Tarpon and Great Hammerheads as a prespawning aggregation and feeding ground. The observed depredation mortality and postrelease predation mortality raise conservation concerns for the fishery. Efforts to educate anglers to improve best practices, including reducing fight times and ending a fight prematurely when sharks are present, will be essential to increase Tarpon survival and reduce shark–angler conflict.

Characteristics and species composition of a small-scale shark fishery in Puerto Rico: Jurisdictional issues enable legal landings of prohibited and endangered species

Shark fishing is increasingly regulated in the Caribbean region. We present new information on the characteristics, landings, species composition, and size composition of the shark fishery of Puerto Rico, a U.S. Caribbean territory, and discuss current regulatory issues. Sharks are mainly landed in a small-scale targeted fishery operating in territory jurisdiction (coast to 17 km) that supplies local demand for inexpensive fish. There are at least 16 species caught: a small number of large Tiger (Galeocerdo cuvier) and Blacktip (Carcharhinus limbatus) sharks and many small but adult Sharpnose sharks (Rhizopriodon spp.) accounted for >80% of landed weight. The catch of Sharpnose sharks was significantly skewed to males. Juvenile Scalloped Hammerhead sharks (Sphyrna lewini) were the second-most caught species but accounted for a small proportion of the landed weight and value given their small size. Differences between territory and U.S. federal regulations (17 km-370 km jurisdiction) leads to legal territory landings of federally prohibited species, especially Scalloped Hammerhead sharks, which might undermine the conservation potential of federal regulations. Scalloped Hammerhead sharks are also listed under the U.S. Endangered Species Act (ESA) making ongoing catches more problematic from a legal perspective. Scalloped Hammerhead shark catch reduction could have minimal livelihood impacts because of their low value, which presents an opportunity for stakeholders to engage on catch reduction measures. This study provides new details on how and why different shark species are caught in Puerto Rico, which could facilitate better management that protects threatened species and maintains livelihoods for people.

Assessment of nursery areas for the scalloped hammerhead shark (Sphyrna lewini) across the Eastern Tropical Pacific using a stable isotopes approach

The scalloped hammerhead shark (Sphyrna lewini) is one of the most iconic marine species across the Eastern Tropical Pacific (ETP), yet little is still known about its reproductive biology and the origin of their nursery areas, despite a continuous global decline in their populations. Understanding the origin of shark nurseries is a complex task; however, it is known that the obtention of resources in the first stages of life of placental sharks occurs through maternal reminiscence, thus it is possible to infer the origin of the energy that neonates accumulate during their gestation. In this study we assessed the ecological connectivity and nursery ground use by undertaking a stable isotope analysis of carbon (δ13C) and nitrogen (δ15N) in skin samples of neonates S. lewini across much of their distribution in the ETP, including the Galapagos Marine Reserve (GMR). Our isotopic mixing models revealed that the S. lewini neonates found in the GMR, have isotopic information similar to adult females inhabit in the Galapagos archipelago, suggesting that they are direct descendants of the females that inhabit the GMR. While neonates found off the continental coasts of Ecuador and Panama have isotopic signatures like those of adult females inhabiting several locations across the ETP. This work provides insight into the origin of nursery areas used by adult S. lewini that aggregate in large numbers across oceanic islands of the ETP, highlighting the value of isotopic models to generate useful information for the conservation of sharks.

High residency of Critically Endangered hammerhead shark to a small area of the Colombian Pacific coast: implications for Marine Protected Area

High residency of Critically Endangered hammerhead shark to a small area of the Colombian Pacific coast: implications for Marine Protected Area

Molecular identification of sharks from the genus Sphyrna (Elasmobranchii: Chondrichthyes) in Maranhão Coast (Brazil).

Sharks of the genus Sphyrna are under intense exploitation globally. In Brazil's northern coast, this genus represents a high proportion of fisheries landings and comprises four species. However, due to difficulty of specific identification when specimens are landed, most of the records are limited to the genus level. Here we analyzed the effectiveness of ITS2 (Internal Transcribed Spacer 2 of rDNA) fragment length protocol (Abercrombie et al., 2005) for identifying hammerhead shark species, comparing with the analysis of COI (Cytochrome oxidase subunit I) and ITS2 sequences. We evaluated samples of muscle tissue acquired in the main fishing ports of Maranhão: Carutapera, Raposa e Tutóia. Sampling was conducted between March 2017 to March 2018 and complemented with material deposited in collection (2015). COI results indicated the occurrence of endangered species which are prohibited to be landed. These include Sphyrna mokarran (67%), S. lewini (15%), S. tudes (3%), and S. tiburo (15%). For the ITS2 marker, we investigated the optimization of the protocol developed by Abercrombie (2005) for to improve the use in this geographical area througout design of a new primers.

Shark and ray monitoring on the marine critical habitat in Aceh Province

Aceh is the leading province in Indonesia, where the marine protection area for juvenile sharks and rays was first established, precisely in Aceh Jaya waters. Rigaih is the fishing port located closest to Aceh Jaya waters, where the angler fish closely with the marine protected area and even intersect with the juvenile’s habitat. This study aimed to examine shark and ray catches in Aceh Jaya before and after establishing the marine protection area. We conducted landing monitoring from 2017 to 2019 (before establishing a conservation area) and monitored in 2020 when the conservation area was established. We recorded that 73% of sharks and ray caught on set gill net. The composition of sharks and rays landed at PPI Rigaih consisted of Sphyrna lewini (75%, n=1783), Chiloscyllium punctatum (8%), Neotrygon caeruleopunctata (7%, n =175), and other species (10%). This study aimed to provide scientific recommendations to support shark conservation action in Aceh Jaya Waters. We found that Aceh Jaya waters are an important area for the life stages of several threatened species, including Scalloped Hammerhead Sharks (S.lewini) and Bottlenose Wedgefish (R.australiae) that are listed in Critically Endangered and listed in Appendix II CITES. Management to support the conservation action needs to be strengthened not only limited to Marine Protected Areas but also fisheries management to reduce the incidental catch of threatened sharks and ray species. Further studies need to be conducted to delineate the habitat range of threatened shark and ray species and identify fishing behaviours that pose a risk for incidental catches of sharks and rays.

Fishery and conservation implications of molecular characterization and traceability of ceviche samples from Pacific Panama

Genetic analysis of 111 samples from ceviche cocktails and fish fillets used for ceviche, obtained from fish markets and processing plants in the Pacific zone of Panama were conducted to determine species composition, trace origin (native, nonnative or imported frozen species) and CITES species status. A total of 21 species were detected (20 fishes and one invertebrate): Coryphaena hippurus (dolphin fish), Pangasianodon hypophthalmus (basa), Trachinotus falcatus (pompano), Cyclopsetta querna (toothed flounder), Atheresthes stomias (arrow-tooth flounder), Lobotes pacificus (Pacific tripletail), Bagre panamensis (Chihuil sea-catfish), B. bagre (Coco sea-catfish), Ariopsis seemanni (Tete sea-catfish), Aspistor luniscutis (yellow sea-catfish), Centropomus viridis (white snook), C. undecimalis (Union snook), Sphyrae naensis (Mexican barracuda), Oreochromis niloticus (Nile tilapia), O. mossambicus (Mozambique tilapia), Cynoscion praedatorius (Boccone weakfish), Protonibea diacanthus (blackspotted croaker), Gadus chalcogrammus (Alaska pollock), Sphyrna lewini (scalloped hammerhead shark), Makaira nigricans (blue marlin) and Dosidicus gigas (giant Humbolt squid). Native species found in ceviche samples were reduced in numbers compared with imported and cultivated ones. Thus, the most common detected fish species was basa, followed by the Nile tilapia and the dolphin fish. This is a positive result in terms of sustainability of local fisheries, since basa is imported as frozen fish meat from Asia. The same applies for Nile tilapia, a cultivated freshwater species not captured from local fisheries. For the dolphin fish, despite being common and exploited in Pacific waters, previous studies suggest its fishery is sustainable in Panama waters. In terms of conservation status, one species cataloged by IUCN as vulnerable (VU), the blue marlin (M. nigricans) and one as critically endangered (CR), the scalloped hammerhead shark (S. lewini) were detected. Sphyrae lewini is also catalog as CITES appendix II. The giant Humbolt squid (D. gigas), classified by IUCN as data deficient (DD), was the only invertebrate detected in samples obtained from a ceviche processing plant. Two sets of primers and dual labeled probes were designed for qPCR eDNA detection of the only CITES species, S. lewini. These represent the first qPCR markers for eDNA detection of S. lewini. Results from this project promote the sustainable use of fishery resources and might provide ceviche producers with a certificate from MarViva Foundation certifying that their ceviche is free of sharks or species threatened/protected by law, giving added value to their product. Molecular detection and molecular traceability are sensitive and species specific, what makes of this tool a reliable method to combat IUU (illegal, unreported and undocumented) fishing.

Trophic ecology shapes spatial ecology of two sympatric predators, the great hammerhead shark (Sphyrna mokarran) and bull shark (Carcharhinus leucas)

Information on how the trophic ecology of predators shapes their movement patterns and space-use is fundamental to understanding ecological processes across organisational levels. Despite this, studies combining spatial and trophic ecology to determine how prey preference and/or resource availability shape space use are lacking in marine predators as these can occur at low density and are often difficult to track over extended periods. Furthermore, many exhibit behavioural variability within species and among closely related, sympatric species adding further complexity. We applied a context-focused, multi-method approach to the understudied great hammerhead shark (Sphyrna mokarran) to test if movement and home ranges relate to prey preference and availability. Movement data from satellite and acoustic telemetry in Queensland, Australia, were combined with stable-isotope analysis, drone surveys, and videos of hunting behaviour. Limited dispersal, and small home ranges in S. mokarran were linked to trophic specialisation on stingray prey. Drone surveys and videos showed predation events on stingrays and demonstrated high, year-round availability of this prey in shallow, inshore habitats, which may allow the majority of S. mokarran to remain resident. This affinity for inshore habitats suggests that critical life-history requirements are performed over local or regional scales, although some larger movements were evident. These results were interpreted in comparison to the well-studied bull shark (Carcharhinus leucas), which showed reliance on pelagic food webs. Carcharhinus leucas had high individual variability in movement, with both large-scale migrations and residency. This could indicate that only some individuals are locally sustained on dynamic, pelagic food webs, while others undergo large-scale excursions over distant habitats. The specialised foraging of S. mokarran indicates they play an apex predator role in shallow, inshore habitats, potentially shaping space-use, and foraging behaviour of batoids. As inshore habitats are disproportionately affected by anthropogenic stressors, S. mokarran’s trophic specialisation and limited demographic connectivity may make the species particularly vulnerable to anthropogenic threats.