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Elasmobranchs, which include sharks and batoids, play critical roles in maintaining the integrity and stability of marine food webs. However, these cartilaginous fish are among the most threatened vertebrate lineages due to their widespread depletion. Consequently, understanding dynamics and predicting changes of elasmobranch communities are major research topics in conservation ecology. Here, we leverage long-term catch data from a standardized bottom trawl survey conducted from 1996 to 2019, to evaluate the spatio-temporal dynamics of the elasmobranch community in the heavily exploited Adriatic Sea, where these fish have historically been depleted. We use joint species distribution modeling to quantify the responses of the species to environmental variation while also including important traits such as species age at first maturity, reproductive mode, trophic level, and phylogenetic information. We present spatio-temporal changes in the species community and associated modification of the trait composition, highlighting strong spatial and depth-mediated patterning. We observed an overall increase in the abundance of the dominant elasmobranch species, except for spurdog, which has shown a continued decline. However, our results showed that the present community displays lower age at first maturity and a smaller fraction of viviparous species compared to the earlier observed community due to changes in species' relative abundance. The selected traits contributed considerably to explaining community patterns, suggesting that the integration of trait-based approaches in elasmobranch community analyses can aid efforts to conserve this important lineage of fish., (© 2023. The Author(s).)

Species-specific monitoring through large shark fin market surveys has been a valuable data source to estimate global catches and international shark fin trade dynamics. Hong Kong and Guangzhou, mainland China, are the largest shark fin markets and consumption centers in the world. We used molecular identification protocols on randomly collected processed fin trimmings (n = 2000) and non-parametric species estimators to investigate the species composition of the Guangzhou retail market and compare the species diversity between the Guangzhou and Hong Kong shark fin retail markets. Species diversity was similar between both trade hubs with a small subset of species dominating the composition. The blue shark (Prionace glauca) was the most common species overall followed by the CITES-listed silky shark (Carcharhinus falciformis), scalloped hammerhead shark (Sphyrna lewini), smooth hammerhead shark (S. zygaena) and shortfin mako shark (Isurus oxyrinchus). Our results support previous indications of high connectivity between the shark fin markets of Hong Kong and mainland China and suggest that systematic studies of other fin trade hubs within Mainland China and stronger law-enforcement protocols and capacity building are needed.

Endangered sharks and rays usually often lack basic information specific to conservation, such as population size. Previous studies have reconstructed shark and ray catch statistics between 1950 and 2019 for the southeast = south of Brazil, but lacking detail at the species level, because the catches were grouped by family, genus or even common name (e.g., skates and rays, Dasyatidae, Rhinobatos, Sphyrnidae, Squatinidae). In this study, we used proportions between species from scientific observer fishing trips and Dirichlet regression modelling to reclassify these categories. This model is a multivariate extension of beta regression and enables the modeling of asymmetric and heteroscedastic compositional data, allowing multinomial data to be obtained in a more informative way. The reconstruction of catches for unclassified data showed a massive dominance of the Squatinidae family until the late 1970s, when catches showed signs of decline. At the same time, the rays of the "emplastro" family showed a progressive increase from 2006 onwards. However, this scenario changed after the reclassification. The category Squatinidae was maintained almost exclusively by S. guggenheim, while 16 categories of species were observed within "emplastro" rays, many of which fall into "endangered", "vulnerable" and "critically endangered" criteria. These reconstructed series provide a more reliable scenario of the catches of thirty elasmobranch species in the southeast and south of Brazil and serve as baseline information for understanding the conservation status of these species. [ABSTRACT FROM AUTHOR]

Copyright of Spanish Journal of Palaeontology is the property of Socieadad Espanola de Paleontologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Threatened shark species are caught in large numbers by artisanal and commercial fisheries and traded globally. Monitoring both which shark species are caught and sold in fisheries, and the export of CITES-restricted products, are essential in reducing illegal fishing. Current methods for species identification rely on visual examination by experts or DNA barcoding techniques requiring specialist laboratory facilities and trained personnel. The need for specialist equipment and/or input from experts means many markets are currently not monitored. We have developed a paper-based Lab-on-a-Chip (LOC) to facilitate identification of three threatened and CITES-listed sharks, bigeye thresher (Alopias superciliosus), pelagic thresher (A. pelagicus) and shortfin mako shark (Isurus oxyrinchus) at market source. DNA was successfully extracted from shark meat and fin samples and combined with DNA amplification and visualisation using Loop Mediated Isothermal Amplification (LAMP) on the LOC. This resulted in the successful identification of the target species of sharks in under an hour, with a working positive and negative control. The LOC provided a simple "yes" or "no" result via a colour change from pink to yellow when one of the target species was present. The LOC serves as proof-of-concept (PoC) for field-based species identification as it does not require specialist facilities. It can be used by non-scientifically trained personnel, especially in areas where there are suspected high frequencies of mislabelling or for the identification of dried shark fins in seizures. [ABSTRACT FROM AUTHOR]

Copyright of Neotropical Ichthyology is the property of Neotropical Ichthyology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Over one third of shark and ray (henceforth elasmobranch) species are threatened by global extinction. Overfishing, driven largely by human consumption of various products is a key threat to >95% of threatened elasmobranch species. The local consumption of elasmobranch meat is an emerging driver of these fisheries particularly in the Global South. Very little data exists on local elasmobranch meat consumption and restaurants offer a useful insight into patterns of consumption. We examined local elasmobranch consumption in India, which has the world's third highest elasmobranch catches. We surveyed 2649 seafood restaurants across 10 coastal states and found that two states alone accounted for 70% of all restaurants serving shark meat. Nine percent of all seafood restaurants advertised elasmobranch meat. 251.6 tonnes, equivalent to 9.8% of India's annual landings, is sold every year in India's restaurants. The drivers of these sales are local cultural affinities and regional cuisines, with evidence of new and evolving consumption pathways, in states like Goa. In Goa, the state with the highest prevalence of elasmobranch meat on restaurant menus, consumption by locals, as well as consumption of "baby sharks" by tourists was driving the demand for elasmobranch meat. Small‐bodied and juvenile sharks of threatened species are at risk from local meat consumption. Elasmobranch meat consumption can be reduced by targeting interventions in the regional hotspots of maximum consumption, substituting other types of seafood as alternatives in regional cuisines, bycatch reduction, increased price and seafood consumer awareness campaigns. Preliminary findings suggest that focusing on the health implications of eating species that concentrate heavy metals will produce the greatest decreases in elasmobranch meat sales at India's restaurants. [ABSTRACT FROM AUTHOR]

While the general diet of Mediterranean elasmobranchs has been widely studied, little is known about food partitioning and competition among sympatric species, despite these being important forces structuring marine communities. Using stomach content and stable isotope analyses, we investigated diet and trophic levels and evaluated the diet overlap and partitioning of Scyliorhinus canicula, Mustelus mustelus, and M. punctulatus in the northwestern Adriatic Sea. These shark species were confirmed as opportunistic mesopredators, but significant differences in their diets emerged. The two bentho-demersal Mustelus species had a larger trophic overlap with S. canicula than between each other. Given the pronounced morphological similarity of these two Mustelus species, this is likely a strategy to limit competition. The strictly benthic S. canicula showed a more varied diet compared to the other species. Stable isotope analysis highlighted that despite the smaller size and overlapping diets, S. canicula occupied a slightly higher trophic level. A better characterization of the trophic role of these species in the food web of the basin can be obtained from these data. At an ecosystem level, this information is essential to evaluate the possible consequences of the decline or recovery of the population of these exploited species. [ABSTRACT FROM AUTHOR]

The silky shark, Carcharhinus falciformis, is a cosmopolitan species commonly caught as a bycatch for longline fisheries. However, the genetic stock structure for the Indo-Pacific Ocean is not well-defined yet. Here, we used eight microsatellite loci to examine the genetic stock structure and effective population size of 307 silky sharks across 5 Indo-Pacific sampling locations. A major genetic break was found between Aceh and the remaining locations (FST = 0.0505–0.0828, p = 0.001). The Indian Ocean displayed a slightly lower effective population estimate (Ne) compared to the Pacific Ocean, potentially due to the higher fishing pressure in the Indian Ocean region. The lowest Ne was found in the Aceh population (Ne = 2.3), suggesting it might be a small and endemic population. These findings offer valuable information for the conservation and management of the silky shark. We suggest that the population around Aceh waters constitutes a distinct stock and should be managed independently. Further investigations into migratory and movement patterns are needed to define the boundaries of different stocks, ensuring effective management the silky shark across the Indo-Pacific region. [ABSTRACT FROM AUTHOR]

Amidst global declines in elasmobranch populations resulting predominantly from overfishing, the need to gather data regarding shark ecology is greater than ever. Many species remain data deficient or at risk of going extinct before sufficient conservation measures can be applied. In this review, we summarise existing knowledge regarding the biology and ecology of the Pacific sharpnose shark Rhizoprionodon longurio (Jordan & Hilbert, 1882), a small‐bodied carcharhinid shark found in coastal waters of the Eastern Tropical Pacific Ocean that is of both commercial and ecological importance. We compare ecological parameters of this species with its closest extant relatives and identify major knowledge gaps and avenues for future research. In particular, additional studies investigating the behavioural and sensory ecology, as well as potential migratory patterns of the species are needed. Such studies will not only improve our understanding of R. longurio, but provide insight into the extent to which the numerous studies performed on a close relative—Rhizoprionodon terraenovae—provide an accurate representation of the biology and ecology of Rhizoprionodon and carcharhinids more generally. [ABSTRACT FROM AUTHOR]

Small coastal demersal sharks form a major proportion of the sharks landed in Malaysia. However, little is known about their feeding ecology and reproduction. This study sought to elucidate the dietary patterns, role of ontogeny in prey consumption, and reproductive biology of four dominant small demersal shark species in Malaysian waters: the Hasselt's bamboo shark, Chiloscyllium hasseltii; brownbanded bamboo shark, C. punctatum; spadenose shark, Scoliodon laticaudus; and Pacific spadenose shark, S. macrorhynchos. Dietary analyses revealed a high overlap in prey taxa consumed; clear resource partitioning among co-occurring species based on the percentage Prey-specific Index of Relative Importance (%PSIRI), with higher fish %PSIRI for Chiloscyllium hasseltii, higher cephalopod %PSIRI for C. punctatum, and higher crustacean %PSIRI for both Scoliodon species; and an ontogenetic diet shift, seen through changes in prey size. Based on the examination of reproductive organs, the results showed larger sizes at maturity for males compared to females for all four species; no obvious reproductive cycles, based on hepatosomatic and gonadosomatic indices for all species; female bias in the sex ratio of the embryos of Scoliodon species; and increased reproductive output (number of eggs or embryos and size of eggs) with larger female size for C. hasseltii and Scoliodon species. The partitioning of food resources minimizes direct competition for food and supports coexistence within shared coastal habitats. The reproductive strategies of these small coastal sharks appear to be favorable for supporting short-term population productivity; although a reduction in fishing pressure, especially from bottom trawlers, is essential for the long-term sustainable use of these sharks. [ABSTRACT FROM AUTHOR]

The shark Squalus albicaudus, categorized by the International Union for Conservation of Nature red list as Data Deficient due to lack of minimal information for classification, is distributed throughout the Brazilian coast. High pressures such as overfishing and anthropic activities, as well as certain biological characteristics, including k strategists, comprise influential shark stocks reduction agents. However, genetic diversity, population structure, connectivity, and effective population size data are still limited for S. albicaudus, indicating the need for further studies. In this context, the genetic variability and population structure of S. albicaudus were investigated herein to test for panmixia. Samples were obtained from coasts of the Brazilian states of Pernambuco, Rio de Janeiro, and São Paulo along the species distribution range, and single nucleotide polymorphisms (SNPs) were assessed by the ddRADseq method. The findings revealed a panmitic S. albicaudus population, explained by certain life strategies, such as polyandry and migratory behavior. Based on the genomic findings reported herein, a single S. albicaudus population should be considered in the study area, indicating the need for specific management and conservation plans at the regional scale. [ABSTRACT FROM AUTHOR]

Juvenile white sharks (JWS) of the Northeastern Pacific population are present in nearshore southern California waters and form mixed size class (~1.5–3 m) aggregations for weeks to months, often within 500 m of shore. These nearshore beach habitats are heavily used for human recreation (e.g., surfing, swimming, body boarding, wading, and standup paddleboarding) and the amount of spatio-temporal overlap between JWS and humans is currently unknown. Increases in human population and the Northeastern Pacific population of white sharks have raised concern over human beach safety. To determine spatio-temporal JWS-human overlap at various spatial scales (e.g., across the entire southern California coastline, across different distances from shore, and within specific beach locations), 26 beach locations across southern California were surveyed monthly resulting in 1644 aerial drone surveys between January 2019 to March 2021. Thirteen environmental variables were assessed to predict when spatio-temporal overlap between JWS and water users was highest. Coast-wide distribution of JWS was clumped, limiting human-shark co-occurrence to specific locations, with 1096 of 1204 JWS observations occurring at Carpinteria and Del Mar Beach locations. Nearshore distribution indicated JWS are often close enough to the wave break to interact with some water users (median = 101 m, range = 2–702 m), although JWS had the most spatial overlap with stand-up paddlers. Daily human-shark co-occurrence was 97% at beaches where JWS aggregations had formed, and human activity showed high spatial overlap at shark aggregation sites. Although there is higher seasonal human-shark spatio-temporal overlap where aggregations form in southern California, the number of unprovoked shark bites across southern California is extremely low. This study provides evidence that high human-shark spatio-temporal overlap does not lead to an increased bite frequency in southern California, and there are a number of possible explanations as to why JWS are not biting water users despite daily encounters. [ABSTRACT FROM AUTHOR]

Chondrichthyes (including sharks, rays, and chimaeras) are a class of jawed cartilaginous fishes (with skeletons composed primarily of cartilage), with major relevance to the marine ecosystems and to humanity. However, cartilaginous fishes are facing various threatens, inflicting abrupt declines in their populations. Thus, critical assessment of available molecular genetic variation, particularly retrieved from Chondrichthyans' transcriptomic analyses, represents a major resource to foster genomics research in this ancient group of vertebrate species. Briefly, RNA-Seq involves the sequencing of RNA strands present on a target tissue, which can assist genome annotation and elucidate genetic features on species without a sequenced genome. The resulting information can unravel responses of an individual to environmental changes, evolutionary processes, and support the development of biomarkers. We scrutinized more than 800 RNA-Seq entries publicly available, and reviewed more than one decade of available transcriptomic knowledge in chondrichthyans. We conclude that chondrichthyans' transcriptomics is a subject in early development, since not all the potential of this technology has been fully explored, namely their use to prospectively preserve these endangered species. Yet, the transcriptomic database provided findings on the vertebrates' evolution, chondrichthyans' physiology, morphology, and their biomedical potential, a trend likely to expand further in the future. [ABSTRACT FROM AUTHOR]

Sharks and rays are among the most threatened vertebrates, mostly due to commercial fisheries. Data on incidental capture is sparse, but it is estimated that about 50% of reported global catches of elasmobranchs are from bycatch. Elasmobranchs are captured in a variety of fishing gear throughout the world. One promising strategy to minimize incidental catches is the release of live sharks and rays. However, so far, no critical analysis had been carried out to assess the importance of release as a measure to mitigate the impacts of bycatch. Results indicated that despite onboard releases being cited in Plans of Action (along ZEEs) and recommendations/regulations of Regional Fisheries Management Commissions (in international waters), this measure is treated as secondary and has voluntary adherence, which can significantly reduce its efficiency. Moreover, among the Best Fishing Practice Manuals currently available, although release is cited as a priority, most of them do not consider the dynamics of the location/fishing modality for which it was developed. A change on how release is perceived is needed to prioritize this conservation strategy, as well as its potential as a social tool to reduce the impacts of bycatch on sharks and rays. [ABSTRACT FROM AUTHOR]

Copyright of Neotropical Ichthyology is the property of Neotropical Ichthyology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The tiger shark (Galeocerdo cuvier) has been relatively well assessed concerning biology and ecology aspects in both Atlantic and Pacific North America and in Caribbean waters. The amount of data in these regions has led to the species protection under capture quotas and with the creation of sanctuaries. The reality in developing countries, however, is the exact opposite, with scarce information on the species in the southern hemisphere, namely South American and African waters. In these regions, protection measures are insufficient, and studies on tiger shark biology and ecology are scarce, significantly hindering conservation and management efforts. Thus, the aim of this study was to compile scientific literature on the tiger shark in the South Atlantic and discuss the impact of these data (or lack thereof) distributed within a total of ten research categories for guiding management plans. In total, 41 scientific publications on different G. cuvier biology and ecology aspects were obtained. The most studied topics were Feeding Ecology (n = 12), followed by Human Interactions (n = 8), and Movements and Migration (n = 7). Northeastern Brazil (Southwest Atlantic) was the most researched area, probably due to the higher coastal abundance of tiger sharks in this area, alongside a high number of recorded attacks, justifying funding for studies in the region. No studies carried out in other South American or African countries were found. It is important to mention that even though some research topics are relatively well covered, a severe knowledge gap is noted for risk assessments and fisheries management, with a proposition for the implementation of sanctuaries noted. This is, however, particularly worrisome, as the South Atlantic is mostly unexplored in this regard for tiger sharks. It is also important to note how different the attention given to this species is in the North Atlantic when compared to the South region. Lastly, we highlight that the existence of sub-populations, the lack of migratory corridors geographically connecting distinct areas used by the species, and the lack of fisheries statistics on tiger shark landings, all increase the vulnerability of this species in the South Atlantic. [ABSTRACT FROM AUTHOR]

Designing appropriate management plans requires knowledge of both the dispersal ability and what has shaped the current distribution of the species under consideration. Here, we investigated the evolutionary history of the endangered gray reef shark (Carcharhinus amblyrhynchos) across its range by sequencing thousands of RADseq loci in 173 individuals in the Indo‐Pacific (IP). We first bring evidence of the occurrence of a range expansion (RE) originating close to the Indo‐Australian Archipelago (IAA) where two stepping‐stone waves (east and westward) colonized almost the entire IP. Coalescent modeling additionally highlighted a homogenous connectivity (Nm ~ 10 per generation) throughout the range, and isolation by distance model suggested the absence of barriers to dispersal despite the affinity of C. amblyrhynchos to coral reefs. This coincides with long‐distance swims previously recorded, suggesting that the strong genetic structure at the IP scale (FST ~ 0.56 between its ends) is the consequence of its broad current distribution and organization in a large number of demes. Our results strongly suggest that management plans for the gray reef shark should be designed on a range‐wide rather than a local scale due to its continuous genetic structure. We further contrasted these results with those obtained previously for the sympatric but strictly lagoon‐associated Carcharhinus melanopterus, known for its restricted dispersal ability. Carcharhinus melanopterus exhibits a similar RE dynamic but is characterized by a stronger genetic structure and a nonhomogeneous connectivity largely dependent on local coral reefs availability. This sheds new light on shark evolution, emphasizing the roles of IAA as source of biodiversity and of life‐history traits in shaping the extent of genetic structure and diversity. [ABSTRACT FROM AUTHOR]

Simple Summary: The reproduction of key reef species is still largely unknown due to difficulties in documenting all elements and steps involved. Sharks are particularly affected by this scarcity of information due to being long-lived species, and witnessing courtship, gestation, and birth is still mostly limited to fortuitous encounters by divers or specimens captured by fishers. Still scarcely described in the literature, our study reports the successful reproduction of Triaenodon obesus in an ex situ environment, which offers an opportunity to observe all steps of the reproduction in detail. Furthermore, we offer the first description of the late embryonic developmental stage based on ultrasound imagery. Elasmobranchs represent a group of species under considerable anthropic pressure because of the scale of industrial and artisanal fisheries and the loss of essential areas for nursery and feeding, which are causing substantial population losses around the world. Reproduction in an ex situ environment enables a healthy population to be built and maintained in networks of public aquariums, increasing our knowledge of elasmobranch reproductive biology and offering the opportunity for reintroductions in areas where native populations have been removed. The study reports two successful pregnancies of the whitetip reef shark Triaenodon obesus, considered a vulnerable species by the International Union for the Conservation of Nature. Copulation and gestation data are provided, including ultrasound recordings of the late stage of embryo development. Ultrasonography was performed with the GE Logiq and convex transducer and revealed a fetus with defined fins and organogenesis, with definition of eyes, gills, liver, a heart with individualized chambers, partially defined kidneys, and a well-defined spiral intestine. A cartilaginous skeleton forming a posterior acoustic shadow was detailed, as well as a moving fetus with a biparietal diameter of 6.47 cm and a heart rate of 62 Beats Per Minute on spectral Doppler. This is the first successful reproduction of T. obesus in an aquarium in Brazil. [ABSTRACT FROM AUTHOR]

Simple Summary: There is a lack of detailed information on the capture pressures and records regarding the tiger shark Galeocerdo cuvier (Péron & Lesueur, 1822) (Carcharhinidae) for the state of Rio de Janeiro, Brazil. This study aimed to expand the tiger shark record database and to improve upon future conservation and management strategies in this area. A total of 23 new records were obtained, increasing the number of tiger shark records off the coast of the state of Rio de Janeiro approximately 5-fold. Possible seasonality patterns concerning tiger shark sizes were noted, indicating the need to consider the coast of Rio de Janeiro as an especially relevant area for at least part of the life history of tiger sharks. The tiger shark Galeocerdo cuvier (Péron & Lesueur, 1822) (Carcharhinidae) is classified as near-threatened along the Brazilian coast, in line with its global categorization. Although Rio de Janeiro, located in southeastern Brazil, is internationally identified as a priority shark conservation area, many shark species, including tiger sharks, are landed by both industrial and artisanal fisheries in this state. However, there is a lack of detailed information on the species capture pressures and records for the state of Rio de Janeiro. Therefore, the aims of this study were to expand the tiger shark record database and to improve upon future conservation and management strategies. Tiger shark records from four coastal Rio de Janeiro regions were obtained by direct observation. The information obtained from fishery colonies/associations, environmental guards, researchers, and scientific articles, totaling 23 records, resulted in an approximately 5-fold increase in the number of tiger shark records off the coast of the state of Rio de Janeiro. A possible seasonality pattern concerning the size of the captured/observed animals was noted, emphasizing the need to consider the coast of Rio de Janeiro as an especially relevant area for at least part of the life history of tiger sharks. [ABSTRACT FROM AUTHOR]

Although sharks have a fundamental role in maintaining the balance of aquatic ecosystems, exerting a great influence on lower levels of the food chain, their populations are declining worldwide due, to a large extent, to overfishing. Of the 64 species registered in Ecuador, from January to December 2019, 19 species were recorded in Manta from the 15,455 captured individuals, with the family Carcharhinidae being the most abundant in the catches (69.4%), and the most abundant species was Prionace glauca (57.9%). Regarding threatened species, such as Carcharhinus longimanus, Sphyrna lewini, and Sphyrna zygaena, a greater presence of immature specimens was observed in landings. However, information on the composition and biological aspects of shark species in the Ecuadorian Pacific is very scarce. Therefore, research on the characteristics of life history (age, growth, and maturity) are of utmost importance for the stock assessments that are being exploited, especially in developing countries, where this information is lacking, causing inadequate management of fishery resources. [ABSTRACT FROM AUTHOR]

Aim: Marine vertebrates play key functional roles on reef ecosystems. Despite their phylogenetic distance, different vertebrate lineages could play similar functions on reefs, which has been overlooked by current research on marine functional biogeography. We provide the first comprehensive assessment of the functional structure and inventory of ecosystem functions delivered by 224 vertebrates—marine mammals, sea turtles, sharks, rays and bony fish—in Atlantic Ocean reefs. Location: Atlantic Ocean reefs. Methods: We compiled six species‐level traits and investigated geographical patterns of functional richness (FRic), functional uniqueness (FUn) and specialization (FSpe) in 83 assemblages. Additionally, we simulate the effects of marine vertebrate species' extinction on functional diversity metrics. Results: Sharks, rays and bony fish species had the highest overlap in functional space (30.94%), while turtles overlapped mainly with bony fishes (1.76%). The functional structure of vertebrate assemblages is not homogeneous across the Atlantic. While functional richness peaks in the Caribbean (a "functional hotspot"), this region depicts low‐to‐intermediate functional uniqueness and functional specialization levels. Despite the large proportion of threatened top predator species (53.1%), mainly large‐bodied sharks, it is the loss of mesopredator species that will severely impact (up to 94% of functional loss) the functional space of vertebrate assemblages in Atlantic Ocean reefs. Main conclusions: Our study reveals that functional richness patterns of vertebrate assemblages differ across Atlantic Ocean reefs. Despite the low values of functional uniqueness and specialization in some reef assemblages, reef functioning can still be compromised due to species' extinctions. The impact of mesopredators' loss over the functional structure of vertebrate assemblages is worrisome since this group holds a considerable proportion of threatened species (20.1%) and is next in line considering the anthropogenic impacts over high trophic level species. [ABSTRACT FROM AUTHOR]

Sharks play a key role in the structure and functioning of marine ecosystems. More ecological information is essential to implement responsible management and conservation actions on this fauna, particularly at a regional level for threatened species. Mustelus mustelus is widely found in the eastern Atlantic Ocean and catalogued as "Vulnerable" by the IUCN European assessment. In this study, data on the distribution and population structure of this species across the islands of the Canarian archipelago, located along an east to west gradient in the north‐eastern Atlantic, were collected by taking advantage of "Local Ecological Knowledge," in terms of sightings in coastal waters and long‐term imprints on the local gastronomic heritage, and decadal fisheries landings. Both sources of quantitative data (sightings and fisheries landings) demonstrated that adults of M. mustelus has a significantly larger presence in the eastern and central, than in the western islands of the archipelago. This is also reflected on local gastronomic legacies, with a larger number of recipes in the eastern and central islands. Adult smooth‐hound sharks were significantly more observed in sandy and sandy‐rocky bottoms, with individuals seen throughout the entire year, whereas juveniles aggregate on very shallow waters in spring and summer. Such aggregations require a special management strategy, as they play a key role in critical life stages; these sites should be protected from human perturbations. We also suggest a temporal fishing ban between April and October, when individuals tend to concentrate on nearshore waters. Because of the large differences in presence of this shark among the Canary Islands, management of the species should be adapted to the specific peculiarities of each island, rather than adopting a management policy at the entire archipelago‐scale. Overall, this study sets the basis for further investigation to promote conservation of this vulnerable shark in the study region. [ABSTRACT FROM AUTHOR]

Increasing fishing pressure has negatively impacted elasmobranch populations globally. Despite high levels of historical and current fishing pressure, the Bay of Bengal region remains data‐poor. Focusing on Bangladesh, we conducted a socio‐ecological study to characterize elasmobranch fisheries and evaluate their impact on threatened species. The results demonstrate that several globally threatened elasmobranch species are frequently captured, and some of them have experienced substantial population declines (e.g., wedgefishes, sawfishes, large carcharhinid sharks) over the past decade. A decrease in elasmobranch diversity, abundance, and size of caught specimens was also reported, which was attributed to increased fishing intensity, destructive practices (e.g., bottom trawling), and an accessible elasmobranch market. While catch and trade of more than 90 elasmobranchs are regulated under Bangladesh's law, non‐compliance is widespread. Likely causes include a dearth of awareness, practical alternative livelihoods, and technical facilities, and the complex nature of the fisheries. Encouraging and facilitating the engagement of fishers in science (data collection), local governance (policy‐making), and field implementation (bycatch mitigation) is vital. These interventions must be rooted in sustainable approaches and co‐designed with fishers, with appropriate training available. Development of this work through enhanced engagement with fishers has the potential to transform the elasmobranch fishery situation in Bangladesh and could be used as a model for data‐poor regions. [ABSTRACT FROM AUTHOR]

Although exceedingly rare, shark attacks have a disproportionately large impact on human behavior, often resulting in shark culls. Due to the invasive nature of shark culls, innovating and testing non-invasive deterrent technologies that may minimize the potential for a rare negative shark encounter has become a conservation priority. One such mitigation approach is barriers, such as exclusion nets and the Sharksafe barrier. With both technologies exhibiting limitations and/or ineffectiveness (e.g., Sharksafe barrier), the development of a more effective technology was warranted. Therefore, this study had two key objectives: (1) to determine if DC 12 Volts 180 Newtons electromagnets can produce deterrent responses in the bull shark (Carcharhinus leucas) and (2) to determine if a newly designed and eco-friendly Exclusion barrier exhibits enhanced C. leucas deterrent capabilities when directly compared to the Sharksafe barrier. Based on 100 baited apparatus trials, electromagnetically treated baits resulted in significantly greater avoidance and reduced feeding frequencies. Furthermore, Poisson generalized linear mixed effect model analyses based on 27, 1-h trials illustrated that the Exclusion barrier region resulted in the greatest avoidance and lowest entrance and exit frequencies when compared to the control and Sharksafe barrier regions. Although the Exclusion barrier did not exclude all interacting sharks, the technology provided superior deterrent efficacy in relation to the Sharksafe barrier. Therefore, with many shark populations exhibiting precipitous declines, continued research on this novel technology on potentially dangerous shark species (e.g., white sharks—Carcharodon carcharias) and in varying ecological conditions (e.g., a high energy coastline) is warranted. [ABSTRACT FROM AUTHOR]

Human activities are rapidly expanding, posing a danger to ocean biodiversity. A review of shark diversity in the Indian Sundarban Biosphere is presented in this present study. Out of the 70 shark species found in the Indian Ocean, researchers discovered 22 have a limited distribution, 12 are quite abundant but not consistently taken, and just 6 have a vast range. Records confirmed the existence of 16 species in Sundarban. Glyphis gangeticus is the sole indigenous species to the Gangetic delta, although it, along with Carcharhinus hemiodon, is uncommon that it was never spotted in the previous decade. [ABSTRACT FROM AUTHOR]

Background: The interplay of animal dispersal and environmental heterogeneity is fundamental for the distribution of biodiversity on earth. In the ocean, the interaction of physical barriers and dispersal has primarily been examined for organisms with planktonic larvae. Animals that lack a planktonic life stage and depend on active dispersal are however likely to produce distinctive patterns. Methods: We used available literature on population genetics and phylogeography of elasmobranchs (sharks, rays and skates) to examine how marine barriers and dispersal ecology shape genetic connectivity in animals with active dispersal. We provide a global geographical overview of barriers extracted from the literature and synthesize the geographical and hydrological factors, spatial and temporal scales to characterize different types of barriers. The three most studied barriers were used to analyse the effect of elasmobranch dispersal potential and barrier type on genetic connectivity. Results: We characterized nine broad types of marine barriers, with the three most common barriers being related to ocean bathymetry. The maximum depth of occurrence, maximum body size and habitat of each species were used as proxies for dispersal potential, and were important predictors of genetic connectivity with varying effect depending on barrier type. Environmental tolerance and reproductive behaviour may also play a crucial role in population connectivity in animals with active dispersal. However, we find that studies commonly lack appropriate study designs based on a priori hypotheses to test the effect of physical barriers while accounting for animal behaviour. Main conclusions: Our synthesis highlights the relative contribution of different barrier types in shaping elasmobranch populations. We provide a new perspective on how barriers and dispersal ecology interact to rearrange genetic variation of marine animals with active dispersal. We illustrate methodological sources that can bias the detection of barriers and provide potential solutions for future research in the field. [ABSTRACT FROM AUTHOR]

Fisheries can act as top predators and affect marine biodiversity and ecosystem functioning via their target species. We studied a coastal food web in the Pacific Ocean that is modular and encompasses 360 species and small- and large-scale fisheries. Small-scale fisheries (SSF), two hammerhead sharks, one stingray, and one flatfish species are network hubs, interacting with multiple species among and within trophic levels (TLs) and modules. SSF and endangered hammerhead sharks act as hyper-hubs, which are network hubs preying on other network hubs and likely imposing widespread top-down effects. Hyper-hubs have two consequences to network structure. First, they show low dietary overlap, connecting the network in complementary ways. Second, they have overlapping indirect interactions, suggesting they can strongly affect each other. Simulations assuming distinct fishery regulations and species extinctions of different TLs and topological roles did not change network structure but redefined hub identity. We hypothesize that competition shapes resource partitioning between fisheries and hammerhead sharks. Our findings suggest that ecosystem-level strategies informed by network approaches can optimize investments to conserve marine ecosystems and ensure food security over coastal areas in the developing world. [ABSTRACT FROM AUTHOR]

Understanding the population dynamics of highly mobile, widely distributed, oceanic sharks, many of which are overexploited, is necessary to aid their conservation management. We investigated the global population genomics of tiger sharks (Galeocerdo cuvier), a circumglobally distributed, apex predator displaying remarkable behavioral versatility in its diet, habitat use (near coastal, coral reef, pelagic), and individual movement patterns (spatially resident to long-distance migrations). We genotyped 242 tiger sharks from 10 globally distributed locations at more than 2000 single nucleotide polymorphisms. Although this species often conducts massive distance migrations, the data show strong genetic differentiation at both neutral (F ST = 0.125–0.144) and candidate outlier loci (F ST = 0.570–0.761) between western Atlantic and Indo-Pacific sharks, suggesting the potential for adaptation to the environments specific to these oceanic regions. Within these regions, there was mixed support for population differentiation between northern and southern hemispheres in the western Atlantic, and none for structure within the Indian Ocean. Notably, the results demonstrate a low level of population differentiation of tiger sharks from the remote Hawaiian archipelago compared with sharks from the Indian Ocean (F ST = 0.003–0.005, P < 0.01). Given concerns about biodiversity loss and marine ecosystem impacts caused by overfishing of oceanic sharks in the midst of rapid environmental change, our results suggest it imperative that international fishery management prioritize conservation of the evolutionary potential of the highly genetically differentiated Atlantic and Indo-Pacific populations of this unique apex predator. Furthermore, we suggest targeted management attention to tiger sharks in the Hawaiian archipelago based on a precautionary biodiversity conservation perspective. [ABSTRACT FROM AUTHOR]

Prior to the Deepwater Horizon (DWH) oil spill, little research effort was focused on studying deep-sea sharks in the Gulf of Mexico (GoM). While the biology of these fishes remains virtually unknown, they are routinely captured in commercial fisheries as bycatch. In the absence of basic biological data, and with the probability of post-release survival unknown for most species, effective management plans cannot be formulated, making populations highly susceptible to overfishing. Any potential detrimental effects of the DWH oil spill, which occurred at 1500 m deep, are also unknown. Following longline capture, we characterized the physiological blood biochemical parameters related to secondary stress and compared them among seven shark species occurring on the continental shelf edge and slope in the GoM at depths ranging from 200 to 2000 m. We also investigated the relationship between blood parameters and depth as well as proximity to the oil spill site. The deep-sea sharks examined here exhibited variability in blood chemistry associated with the secondary stress response, with values falling within published records for previously studied elasmobranchs. Results suggested that there is greater relative physiological stress in shallower-dwelling sharks as well as smaller-bodied sharks. Further, the rate of core temperature warming was fastest in smaller bodied sharks, which likely contributes to greater physiological stress. The core temperatures of the larger-bodied, deeper-dwelling species were not altered as drastically as the smaller-bodied sharks after being hauled to the surface. Any chronic physiological effects of the oil spill were not detectable as there were no relevant correlations between blood chemistry metrics and proximity to the DWH oil spill site. [ABSTRACT FROM AUTHOR]

Historically, Brazilian fisheries management has not considered the knowledge of fish taxonomy from within fishing communities. This study points out processes of recognition, classification and nomenclature of sharks achieved by fishermen from South Bahia, Brazil. Data were obtained through semistructured interviews visually stimulated by exhibiting images of 30 species of elasmobranch fishes. Regionally, elasmobranch species are inserted into the folk taxon called "leather fishes" and in a category known as "cação" (shark) family. In addition to hierarchical classification, the fishermen organize shark species by adopting an ethnodimorphic and sequential model based on ethnoontogeny. Ethnodiagnostic characteristics are mainly related to the morphology, ecology and even physiology of a species. A total of 144 epithets is recorded, with a mean value of 4.8 ethnospecies for each scientific correspondent. Richness of vernacular names impedes species-specific information gathering regarding shark landings if fisher knowledge is not considered and applied in the improvement of fisheries data. Thus, this study encourages the employment of fishermen as parataxonomists in order to assist in the identification of sharks to specific levels. This study further emphasizes the potential of using ethnotaxonomic knowledge of fishing communities in initiatives related to participative management of shark fisheries in developing countries. [ABSTRACT FROM AUTHOR]

The smalltail shark, Carcharhinus porosus, was the most abundant elasmobranch species in fisheries off Brazil's northern coast (BNC) in the 1980s, but its population has been declining since the 1990s. For this reason, a demographic analysis is necessary to determine the extent of this decline and the fishing effect on the BNC's population. Therefore, we performed a stochastic demographic analysis of the population in the BNC, and considered its global center of abundance. Smalltail shark specimens (n = 937) were collected with gillnets in Maranhão state, eastern BNC, in the 1980s with sizes ranging between 29.6 and 120.0 cm total length. Most of the individuals (90.6%) caught were juveniles (< 6 years-old), and the mortality and exploitation rates showed that the species was overexploited (92.3% above the fishing mortality corresponding to the population equilibrium threshold). The smalltail shark's biological characteristics, such as slow growth and low fecundity, demonstrate that it is one of the least resilient species among similar sized coastal sharks in the region. All these factors yielded an annual decrease of 28% in the intrinsic population growth rate, resulting in a population decline of more than 90% in only 10 years, and much higher for the current period. This set of features comprising fishing recruitment occurring upon juveniles, overfishing, and intrinsically low resilience make the population unable to sustain fishing pressure and severely hamper biological recruitment, thus causing this drastic population decline. Furthermore, several local extinctions for this species in the northeastern and southeastern regions of Brazil highlight its concerning conservation scenario. Therefore, since similar fisheries characteristics occur throughout its distribution range, C. porosus fits the criteria E of the IUCN Red List for a critically endangered species and urgent conservation measures are needed to prevent its extinction in the near future. [ABSTRACT FROM AUTHOR]

The U.S. Congress is currently discussing the Shark Fin Sales Elimination Act to eliminate shark fin trade at the federal level. This bill was introduced in 2017 and has been proceeding very slowly in Congress because of mixed reviews from the scientific community. Debate exists on whether shark conservation and management are effectively addressed with tightened trade controls for imported shark products or blanket bans that outright end U.S. participation in the shark fin trade. Here we contribute to this debate with a review and analysis of economic, nutritional, ethical, and legal arguments, as well as of the shark fisheries status and shark fin trade. We show that the United States has a limited commercial interest in shark fisheries and contributes to the shark fin trade mainly as a facilitator. A fin trade ban has few tangible economic drawbacks but would have a considerable conservation impact. While making all shark fisheries sustainable is the ultimate goal, in practice this objective is far from achievable everywhere in the world. Conversely, banning shark fin trade is an interim measure that nations like the United States can take with negligible cost and can truly impact the biggest driver of shark exploitation globally. [ABSTRACT FROM AUTHOR]

During their evolutionary history, modern sharks developed different tooth mineralization patterns that resulted in very distinct histological patterns of the tooth crown (histotypes). To date, three different tooth histotypes have been distinguished: (i) orthodont teeth, which have a central hollow pulp cavity in the crown, encapsulated by a prominent layer of dentine (orthodentine); (ii) pseudoosteodont teeth, which have their pulp cavities secondarily replaced by a dentinal core of porous dentine (osteodentine), encased by orthodentine; and (iii) osteodont teeth, which lack orthodentine and the whole tooth crown of which consists of osteodentine. The aim of the present study was to trace evolutionary trends of tooth mineralization patterns in modern sharks and to find evidence for the presence of phylogenetic or functional signals. High resolution micro‐computed tomography images were generated for the teeth of members of all nine extant shark orders and the putative stem group †Synechodontiformes, represented here by three taxa, to examine the tooth histology non‐destructively. Pseudoosteodonty is the predominant state among modern sharks and represents unambiguously the plesiomorphic condition. Orthodonty evolved several times independently in modern sharks, while the osteodont tooth histotype is only developed in lamniform sharks. The two shark orders Heterodontiformes and Pristiophoriformes showed highly modified tooth histologies, with Pristiophorus exhibiting a histology only known from batomorphs (i.e. rays and skates), and Heterodontus showing a histological difference between anterior and posterior teeth, indicating a link between its tooth morphology, histology and durophagous lifestyle. The tooth histotype concept has proven to be a useful tool to reflect links between histology, function and its taxonomic value for distinct taxa; however, a high degree of variation, especially in the pseudoosteodont tooth histotype, demonstrates that the current histotype concept is too simplistic to fully resolve these relationships. The vascularization pattern of the dentine might offer new future research pathways for better understanding functional and phylogenetic signals in the tooth histology of modern sharks. [ABSTRACT FROM AUTHOR]

A global analysis of the diet of chondrichthyes (23 species) was conducted during one bottom-trawl research cruise in the region where the highest catches of skates occurred off southwestern Atlantic. The diet was quantified by calculating the percentage frequency of occurrence of each prey. The influence of variables total length, sex, maturity stage, predator species, morphtype (sharks, skates, batoids), and depth on the diet was evaluated by fitting generalized linear models. The diet composition of chondrichthyes consisted mainly of crustaceans, polychaetes, and fish. The study region constituted a feeding ground for the majority of chondrichthyans species analyzed. The diet of chondrichthyes exhibited inter-specific differences sorted into three major trophic guilds and global ontogenetic shift. The consumption of crustaceans and polychaetes decreases with the total length of the chondrichthyes, whereas the consumption of fish increases as the predator grew in size. In addition, prey size of fish and crabs increased with increasing body size of predator, but large chondrichthyes also continued to feed on relatively small crabs. Trophic partitioning and ontogenetic diet shifts may act synergistically, favoring the coexistence of at least 23 species of chondrichthyes at all stages of their life histories, limiting the direct competition for food. [ABSTRACT FROM AUTHOR]

Peru is one of the world’s leading fishing nations and its seafood industry relies on the trade of a vast variety of aquatic resources, playing a key role in the country’s socio-economic development. DNA barcoding has become of paramount importance for systematics, conservation, and seafood traceability, complementing or even surpassing conventional identification methods when target organisms show similar morphology during the early life stages, have recently diverged, or have undergone processing. Aiming to increase our knowledge of the species diversity available across the Peruvian supply chain (from fish landing sites to markets and restaurants), we applied full and mini-barcoding approaches targeting three mitochondrial genes (COI, 16S, and 12S) and the control region to identify samples purchased at retailers from six departments along the north-central Peruvian coast. DNA barcodes from 131 samples were assigned to 55 species (plus five genus-level taxa) comprising 47 families, 24 orders, and six classes including Actinopterygii (45.03%), Chondrichthyes (36.64%), Bivalvia (6.87%), Cephalopoda (6.11%), Malacostraca (3.82%), and Gastropoda (1.53%). The identified samples included commercially important pelagic (anchovy, bonito, dolphinfish) and demersal (hake, smooth-hound, Peruvian rock seabass, croaker) fish species. Our results unveiled the marketing of protected and threatened species such as whale shark, Atlantic white marlin, smooth hammerhead (some specimens collected during closed season), shortfin mako, and pelagic thresher sharks. A total of 35 samples (26.72%) were mislabeled, including tilapia labeled as wild marine fish, dolphinfish and hake labeled as grouper, and different shark species sold as “smooth-hounds”. The present study highlights the necessity of implementing traceability and monitoring programs along the entire seafood supply chain using molecular tools to enhance sustainability efforts and ensure consumer choice. [ABSTRACT FROM AUTHOR]

This study describes the pathologic findings of 24 humpback whales (Megaptera novaeangliae) found stranded along the Brazilian coast from 2004 to 2016. Eighteen (75%) animals evaluated were found stranded alive. From these, 13 died naturally on shore and five were euthanized. Six died at sea and were washed ashore. Of the 24, 19 (79.2%) were calves, four (16.7%) were juveniles, and one (4.2%) was an adult. The most probable cause of stranding and/or death (CSD) was determined in 23/24 (95.8%) individuals. In calves, CSD included neonatal respiratory distress (13/19; 68.4%), infectious disease (septicemia, omphaloarteritis and urachocystitis; 3/19; 15.8%), trauma of unknown origin (2/19; 10.5%), and vehicular trauma (vessel strike; 1/19; 5.3%). In juveniles and adult individuals, CSD was: emaciation (2/5; 40%), sunlight-thermal burn shock (1/5; 20%); and discospondylitis (1/5; 20%). In one juvenile, the CSD was undetermined (1/5; 20%). This study integrates novel findings and published case reports to delineate the pathology of a South-western Atlantic population of humpback whales. This foundation will aid in the assessment of the population health and establish a baseline for development of conservation policies. [ABSTRACT FROM AUTHOR]

Increasing fishing effort has caused declines in shark populations worldwide. Understanding biological and ecological characteristics of sharks is essential to effectively implement management measures, but to fully understand drivers of fishing pressure social factors must be considered through multidisciplinary and integrated approaches. The present study aimed to use fisher and trader knowledge to describe the shark catch and product supply chain in Northeastern Brazil, and evaluate perceptions regarding the regional conservation status of shark species. Non-systematic observations and structured individual interviews were conducted with experienced fishers and traders. The demand and economic value of shark fins has reportedly decreased over the last 10 years while the shark meat trade has increased slightly, including a small increase in the average price per kilogram of meat. Several threatened shark species were reportedly often captured off shore and traded at local markets. This reported and observed harvest breaches current Brazilian environmental laws. Fishing communities are aware of population declines of several shark species, but rarely take action to avoid capture of sharks. The continuing capture of sharks is mainly due to a lack of knowledge of environmental laws, lack of enforcement by responsible authorities, and difficulties encountered by fishers in finding alternative income streams. National and regional conservation measures are immediately required to reduce overfishing on shark populations in Northeastern Brazil. Social and economic improvements for poor fishing communities must also be implemented to achieve sustainable fisheries. [ABSTRACT FROM AUTHOR]

Understanding the trophic interactions and the position of species within a foodweb is crucial if we want to understand the dynamics of marine communities and the impact individual components of the community have on trophic network compartments. Recent studies have indicated sharks and rays are important elements within foodwebs. In this study, we evaluated the ecological importance of sharks and rays in a subtropical ecosystem off the coast of southern Brazil by using topological analyses. We tested the hypotheses that some elasmobranchs can be considered key elements within the foodweb, and that large predators have topological importance (act as keystones), so that, when large predators are excluded, mesopredator elasmobranchs occupy higher topological positions. Our results indicate that Galeocerdo cuvier, Carcharhinus obscurus, Carcharias taurus, Sphyrna lewini and S. zygaena are species with large ecological function values and may exert a powerful influence over lower levels. These issues need to be considered by conservation and fishery management groups since it appears that ecosystem integrity may be compromised by reductions in the populations of large predators. Carcharhinus obscurus, S. zygaena and Zapteryx brevirostris were found to be the elasmobranchs with largest values of centrality, and can, therefore, be considered key elements in the topological structure. [ABSTRACT FROM PUBLISHER]

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Mislabelling of fish and fish products has attracted much attention over the last decades, following public awareness of the practice of substituting high-value with low-value fish in markets, restaurants, and processed seafood. In some cases, mislabelling includes illegal, unreported, and unregulated (IUU) fishing, contributing to overexploit substitute species that are undetectable when sold under wrong names. This is the first study of DNA barcoding to assess the level of mislabelling in fish marketed in Ghana, focusing on endangered shark species. Genetic identification was obtained from 650 base pair sequences within the cytochrome c oxidase I (COI) gene. All except one of 17 shark fillets analysed were wrongly labelled as compared with none of 28 samples of small commercial pelagic fish and 14 commercial shark samples purchased in Europe. Several substitute shark species in Ghana are endangered (Carcharhinus signatus and Isurus oxyrinchus) and critically endangered (Squatina aculeata). Shark products commercialized in Europe (n = 14) did not reveal mislabelling, thus specific shark mislabelling cannot be generalized. Although based on a limited number of samples and fish markets, the results that reveal trade of endangered sharks in Ghana markets encourage Ghanaian authorities to improve controls to enforce conservation measures. [ABSTRACT FROM AUTHOR]

Angel sharks are distributed worldwide in tropical to subtropical waters. Across the Eastern Pacific Ocean (EPO), two valid species are reported: The Pacific angelshark Squatina californica and the Chilean angelshark Squatina armata; however, there is still uncertainty about their geographic distribution, mainly along the northern Peru coast where the species have been reported to be sympatric. The aim of this study is to describe the genetic differences between the genus Squatina from the EPO, including samples from northern Peru, and using DNA barcoding and three species delimitation models: Poisson tree processes (PTP) model, Bayesian implementation of the PTP (bPTP) model and the general mixed Yule coalescent (GMYC) model. The three approaches summarized 19 nominal Squatina species in 23 consensus Molecular Taxonomic Units (MOTU). Only 16 of them were in accordance with taxonomic identifications. From the EPO, four Squatina MOTUs were identified, one from North America (S. californica USA/Mexico) and three sampled in northern Peru, S. californica Peru, S. armata and Squatina sp. (a potential new species). This study contributes to the management and conservation policies of angel sharks in Peru, suggesting the presence of an undescribed species inhabiting the northern Peruvian coast. The use of molecular approaches, such as DNA barcoding, has the potential to quickly flag undescribed species in poorly studied regions, including the Southeast Pacific, within groups of ecologically and economically important groups like angel sharks. [ABSTRACT FROM AUTHOR]

Simple Summary: Sharks rely on a diet with high lipid content, depending on gallbladder proper functioning for lipid emulsification, absorption, and subsequent hepatic storage. The present study reports a physiological impairment due to bile accumulation in juvenile tiger sharks and the possible causes of such condition. Physiological adaptations have evolved to help sharks face rapid periods of feast. Tiger sharks are generalist apex predators that rely on a high-lipid/protein diet. To achieve a satisfactory nutritional condition, proper lipid absorption and hepatic storage are needed. Bile secretion in sharks is low and sporadic but increases during short periods of fasting. The present study describes a physiological impairment caused by bile accumulation in juvenile tiger sharks, possibly due to prolonged fasting. These evidences suggest that, even though sharks have adaptations that prevent them from dying from starvation, alarming physiological alterations might occur. Future studies are needed to assess how such a condition can affect wild populations, as well as possible sublethal consequences that could impact their long-term survival. [ABSTRACT FROM AUTHOR]