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Occurrence of multiple whitetip reef sharks Triaenodon obesus in the Atlantic Ocean is reported for the first time from near a sunken ferry off the Paraná coast in south‐eastern Brazil. This occurrence is hypothesized to have been caused by either a human introduction or a remarkably long oceanic displacement. [ABSTRACT FROM AUTHOR]

Context: The blackspot shark (Carcharhinus sealei) is a small-bodied coastal shark often incidentally caught in fisheries across South-east Asia. Aims: This study aimed to document the species' biology, ecology, fisheries and markets to inform conservation. Methods: In total, 103 blackspot sharks from Indonesia (n = 101) and Singapore (n = 2) were examined to determine biological parameters (growth rate, age at maturity, reproductive traits and diet). An interview with a Singaporean seafood supplier gave insight to population trends, fisheries and markets. Key results: Males attained a maximum age of 9 years, the smallest mature individual measured 709-mm stretched total length (STL), with 50% reaching maturity at 6.15 years. Females attained a maximum age of 11 years, the smallest mature individual measured 730 mm STL, with 50% reaching maturity at 6.12 years. The species has an overall growth rate (k) of 0.37 year−1. Reproduction was asynchronous, with only two pups produced per litter. Crustaceans dominated the diet of juveniles, whereas bony fishes and cephalopods dominated the diets of adult males and adult females respectively. Conclusions: Blackspot sharks have a moderately fast growth rate, but a late age-at-maturity and a low fecundity. Diet differed between the sexes as well as adults and juveniles. Implications: The low fecundity and late maturity of blackspot sharks increase their vulnerability to exploitation. Blackspot sharks are now listed on CITES-Appendix II, but mortality may remain high because they are reportedly often caught incidentally. Blackspot sharks from Riau Islands, Indonesia, have a late maturity (~6 years old) and low fecundity (litters of two pups). Mature males primarily eat bony fishes, mature females primarily eat cephalopods, whereas juveniles primarily eat crustaceans. A seafood supplier who was interviewed has perceived population declines and stated that the species is mostly caught incidentally. [ABSTRACT FROM AUTHOR]

Catch-and-release angling is a popular recreational pastime and an essential component of many fish research programmes. Marked physiological disturbances have been documented in elasmobranchs in response to angling and handling, but skates and rays remain understudied. Here, we describe for the first time the physiological responses of the critically endangered flapper skate (Dipturus intermedius) to angling, handling and tagging in Scotland. Sixty-one skate were captured by angling as part of a tagging research programme. We assessed individual health, measured blood parameters at two time points (post-capture and prior to release) and recorded heart and respiratory rates during handling and the surgical insertion of acoustic tags. Injuries or infections were identified in 10% of individuals and attributed to prior angling in two cases. Skate generally experienced a mild metabolic acidosis characterized by decreases in blood pH and bicarbonate and increases in lactate and glucose. Respiratory acidosis characterized by limited increases in PCO2 was also observed. The degree of acidosis was greater with warmer sea temperatures and longer fight times, and worsened during the time that skate were handled on deck. Heart rates during handling were negatively associated with body size, positively associated with temperature and also linked to time on the line. Taken together, our results suggest that elevated fight times and temperatures increase the physiological stress experienced by rod and reel-caught flapper skate. Efforts to reduce fight times and minimize heat exposure (including shading, irrigation and reduced handling time) should be beneficial for skate. [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]

Sharks and rays evolved 450 million years ago, during the Late Ordovician Period. However, during the modern Anthropocene, shark populations have declined at considerable rates, and recent global assessments indicate about one in three species is threatened with extinction. A notable reason for this elevated extinction risk is overfishing linked to increased demand for shark fins and other products. Here, we review multiple dimensions of consuming shark products, ranging from stock sustainability, product (mis)labelling and trade, the human health implications of consuming shark products, and illegal, unreported and unregulated fishing and slavery and labour abuses in the fishing industry. We conclude that traceability and increased transparency in seafood supply chains is essential to overcome obstacles to consumption of sustainable, ethical and healthy shark products. We also provide a decision tree outlining steps in consumer choice that would foster such consumption. Our aim is to provide a holistic view on issues concerning the consumption of shark products that will help policymakers, the public, management and law enforcement agencies to advocate for ecologically‐ and ethically sustainable consumption of shark products and thereby empower the general public to make informed decisions on which shark products they consume. [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]

Anthropogenic actions have affected marine species for a long time, through overexploitation of natural stocks and habitat degradation, influencing the life strategies of several taxa, especially rays and sharks, which have suffered significant population declines in recent years. Therefore, conservation actions and stock management have become paramount. In this regard, chola guitarfish, Pseudobatos percellens, distributed throughout the Brazilian coast, is often commercially fished by local artisanal fleets or as by-catch in shrimp trawl fisheries. Therefore, this study aimed to understand the genetic diversity of P. percellens throughout the Brazilian coast, using single nucleotide polymorphisms (SNPs). Genetic analyses employing 3329 SNPs revealed a hidden biodiversity within P. percellens, with at least one lineage occurring in the Northern and Northeastern regions and another distributed in the Southeastern/Southern Brazilian coast, with high genetic differentiation between them. However, the Discriminant Analysis of Principal Components (DAPC) indicated the presence of in fact three lineages distributed in these regions that must still be better investigated. Therefore, to ensure adequate conservation of chola guitarfish biodiversity, populations must be managed separately along the Brazilian coast. Furthermore, the need for a taxonomic review for this group is noted. [ABSTRACT FROM AUTHOR]

The age and growth of Urotrygon microphthalmum were studied using specimens captured between March 2010 and March 2012 as by-catch in the shrimp trawl fishery off the coast of the state of Pernambuco, Brazil. A total of 347 vertebrae were read, 161 from males (81.6–249.55 mm) and 186 from females (86.15–298.1 mm). The estimated average percentage index (IAPE) ranged from 0.71% to 4.33% (mean = 2.5%) in vertebrae from specimens with 1 and 6 band pairs, respectively. In the present study, the different approaches to validation produced variable results (partially valid growth zones). We then decided to discuss the growth of the species considering the formation of an annual ring. There were statistically significant differences in growth between the sexes. The best model to describe male growth was the von Bertalanffy growth model for two phases (VBGM TP) with growth parameters L∞ (maximum theoretical length) = 230.35 mm, k (growth constant) = 1.00, t0 (theoretical age of size zero) = −0.76 years and for females it was the von Bertalanffy with birth size (VBGM L0) model with parameters L∞ = 282.55 mm, k = 0.37. The age of maturity for males and females was 1.52 and 2.02 years, respectively, and the maximum age observed was 5.5 and 8.5 years, respectively. Despite being a fast-growing species, Urotrygon microphthalmum is threatened, probably due to the high mortality levels from shrimp trawling in a very narrow range of the shelf where all the life stages are captured. [ABSTRACT FROM AUTHOR]

Bull shark (Carcharhinus leucas) is a near‐threatened elasmobranch species capable of moving between the fresh and salty waters of tropical and subtropical coastal areas, for which we still lack important ecological information. During their first years of life, bull sharks use estuarine systems as nursery areas, making them highly susceptible to environmental and anthropogenic pressures. We studied the trophic ecology of juveniles found in the Coyote estuary, a potential nursery area in Costa Rica, to understand the potential impact of further bull shark declines and gain knowledge that could aid in their conservation. We analysed the trophic ecology of juvenile bull sharks [81–103 cm total length (TL)] in the Coyote estuary, Costa Rica, using stable isotopes of δ15N and δ13C. Since one problem using this technique in juveniles is the confounding effect of the maternal signature, we sampled different tissues (muscle and plasma), verified the status of the shark's umbilical scar and identified the size at which the isotope signature is a result of the animal's current diet. The isotopic values of the muscle tissue reflected the maternal isotopic signature. In contrast, plasma values reflected the diet of juvenile bull sharks >95 cm TL and with a closed umbilical scar. Juvenile bull sharks fed primarily on teleost fishes of the order Anguilliformes and Siluriformes, and have a high trophic position (≥4.0) in the Coyote estuary. Our findings suggest that this estuary is an important feeding site for juvenile bull sharks of the Pacific of Costa Rica. Thus, the protection of essential habitats such as the Coyote estuary will benefit not only bull shark conservation, but also the conservation of an array of fish species that also use this habitat as a rookery, many of which are of commercial interest. [ABSTRACT FROM AUTHOR]

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]

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]

This is the first reported record of stable isotope values for elasmobranch rays within Malaysian waters, and serves as an important baseline methodological information for future studies investigating stable isotope values in both shark and ray species in the region. This study examined the effects of urea removal on the stable isotopes values of d13C and d15N in muscle tissues sampled from several elasmobranch rays species, namely Pastinachus atrus, Rhinoptera javanica, Himantura gerrardi, Himantura uarnak and Aetobatus ocellatus. Individual ray species were collected in July and August of 2018, from the coastal waters of Terengganu State, Malaysia. Urea removal was performed by soaking muscle tissue samples in deionised water for at least 24 hours before being dehydrated. The resulting stable isotope values of these samples were compared to samples that did not undergo the urea removal process. Stable isotope values were individual and species-specific, however, the effect of urea removal was significant for d15N values but did not significantly affect the d13C values. We conclude that removing urea from elasmobranch samples before stable isotope analysis is advisable to draw correct conclusions about the animal's diets. [ABSTRACT FROM AUTHOR]

Trophic ecology studies on predator–prey interactions reveal insights into ecological communities and help understand a species' role in the food web by contributing to improved fisheries management and conservation capabilities. Understanding the ecological role of overexploited and endangered predators is essential to deciphering how their feeding behaviour influences food web dynamics. In this study, the authors investigated the feeding behaviour of the common and IUCN‐listed Near Threatened (NT) thornback ray Raja clavata, using carbon and nitrogen stable isotope and stomach content analysis (SCA). It has recently suffered an 87% decline in reported catches from the Sea of Marmara within the last decade. These results show that thornback ray mainly feeds on teleost species, except in summer, with both methods showing this species changes its diet ontogenetically by SCA. This ontogenetic diet shift was at lengths 40–50 cm by changing group preferences from Crustacea to Teleostei. MixSIAR results showed that both adult and juvenile individuals of R. clavata feed mainly on the crustaceans, but the contribution of teleosts represented by Trachurus sp. was very low (<15%). The trophic position increased total length and was higher than other batoid species in the Sea of Marmara. [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]

Elasmobranchs have a very distinct metabolism, and many aspects related to the energetic dynamics of these animals remain poorly investigated. The reproductive period is particularly vulnerable for viviparous species, as part of the energy reserves of the parental biomass is reallocated for gamete production and embryo development. In this context, this study aimed to characterize parental metabolite provisioning to the offspring (both sperm and developing embryos) of the Brazilian Guitarfish, Pseudobatos horkelii , through glucose, β-hydroxybutyrate, triglycerides, and total cholesterol determinations in the uterine liquid (UL) and serum of pregnant females and in the seminal fluid (SF) and serum of males during the copulation period. No significant difference was observed for the analyzed markers between the UL and SF. Except for triglycerides, higher in female serum samples, all other energy markers were present at similar concentrations in the serum of both females and males. When comparing female UL and serum, significant differences were observed for triglycerides and total cholesterol. No differences were observed between SF and serum in males. The results indicate that all markers are being made available to offspring, possibly complementary to the yolk in the case of maternal liquid, and as an additional source for sperm mobilization required during egg fertilization in the case of the paternal fluid. Correlations between the markers in the parental matrices were also noted, compatible with the metabolic pathways activated during energy mobilization in vertebrates. Moreover, distinct marker predominance patterns were also noted for both UL and SF. Energy mobilization characterization directed to offspring through parental fluids aids in unraveling metabolic dynamics during the reproduction stage while also providing support for stress physiology studies to evaluate the indirect effects of parental allostatic overload in both sperm and developing embryos. Finally, energy mobilization assessments of parental fluids may also help elucidate how internal fertilization and viviparity evolved in this very distinct taxonomic group. [ABSTRACT FROM AUTHOR]

The present paper represents the first description of abnormal hermaphroditism in Galeus melastomus (Rafinesque, 1810). The black mouth cat shark specimen, collected in summer from southern Tyrrhenian Sea at the entrance of Salerno gulf, showed a basic intersexuality characterized by the presence of male secondary and female primary sexual characters. The reproductive system has been described with an accurate morphological analysis, also including a histological assessment of oocytes. Results showed the presence of only right clasper, not exceeding the pelvic fin in length, with the absence of internal males' sexual organs. Concerning the female primary characters, the analysis of histological assessment showed the structure of mature oocyte, confirming the maturity stage of a mature female in active extruding stage, as highlighted by the macroscopic morphological analysis. Despite in many marine organisms' hermaphroditism is a physiological condition showed by specimens during their lifecycle, in Elasmobranchs this is considered an abnormal condition, with some exceptions. The lack of information on hermaphroditism in elasmobranchs form the Mediterranean Sea requires an increase of scientific community's attention, improving the knowledge on the reproductive biology of this sensitive taxon. This is essential to enhance the conservation of elasmobranchs populations in the entire Mediterranean basin. [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]

Giant guitarfishes (Glaucostegidae) and wedgefishes (Rhinidae) are some of the most threatened marine taxa in the world, with 15 of the 16 known species exhibiting global population declines and categorized as Critically Endangered according to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. The recent inclusion of all species in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) necessitates more rigorous enforcement by regulatory authorities.Challenges in regulating the trade of giant guitarfish and wedgefish products due to difficulties in visual identification of processed products and labelling issues impede enforcement. The aim of this study is to characterize the diversity and origins of associated traded products that were commercially available in Singapore, one of the world's top importers and re‐exporters of shark and ray products.A total of 176 samples of elasmobranch products were obtained between June and December 2019 from fishery ports and various retailers in Singapore. By applying cytochrome c oxidase subunit I gene barcoding, 31 elasmobranch species were detected, with 55% of the species considered threatened (Critically Endangered, Endangered, or Vulnerable) based on the IUCN Red List and 35% of species listed in CITES Appendix II. Four species of giant guitarfishes and wedgefishes were commercially available to consumers in fresh forms of whole fish, fillet, and fin, as well as dried and cooked meats.DNA barcoding has proven to be an effective tool for identifying elasmobranch products that are impossible to recognize visually and would aid enforcement of CITES trade regulations. This work underscores the urgent need to step up enforcement of marine wildlife regulations and draw public attention to the elasmobranch trade. [ABSTRACT FROM AUTHOR]

Animal dietary information provides the foundation for understanding trophic relationships, which is essential for ecosystem management. Yet, in marine systems, high‐resolution diet reconstruction tools are currently under‐developed. This is particularly pertinent for large marine vertebrates, for which direct foraging behaviour is difficult or impossible to observe and, due to their conservation status, the collection of stomach contents at adequate sample sizes is frequently impossible. Consequently, the diets of many groups, such as sharks, have largely remained unresolved. To address this knowledge gap, we applied metabarcoding to prey DNA in faecal residues (fDNA) collected on cotton swabs from the inside of a shark's cloaca. We used a previously published primer set targeting a small section of the 12S rRNA mitochondrial gene to amplify teleost prey species DNA. We tested the utility of this method in a controlled feeding experiment with captive juvenile lemon sharks (Negaprion brevirostris) and on free‐ranging juvenile bull sharks (Carcharhinus leucas). In the captive trial, we successfully isolated and correctly identified teleost prey DNA without incurring environmental DNA contamination from the surrounding seawater. In the field, we were able to reconstruct high‐resolution teleost dietary information from juvenile C. leucas fDNA that was generally consistent with expectations based on published diet studies of this species. While further investigation is needed to validate the method for larger sharks and other species, it is expected to be broadly applicable to aquatic vertebrates and provides an opportunity to advance our understanding of trophic interactions in marine and freshwater systems. [ABSTRACT FROM AUTHOR]

The age and growth of subtropical populations of the Brazilian and Caribbean sharpnose sharks (Rhizoprionodon lalandii and R. porosus respectively) were determined by combining direct and indirect ageing methods, maximising the use of available information. Using vertebrae ageing for R. lalandii , the theoretical maximum length L ∞ and growth coefficient k were 661.9 mm and 1.14 year–1 for males and 751.7 mm and 0.59 year–1 for females. Vertebrae were not sampled for R. porosus. Values of L ∞ and k from electronic length–frequency analyses (ELEFAN) were 762 mm and 0.71 year–1 for male R. lalandii , 791 mm and 0.67 year–1 for female R. lalandii , 1040 mm and 0.41 year–1 for male R. porosus and 1165 mm and 0.31 year–1 for female R. porosus. Growth during the first year of life in relation to birth size was 80.3% for R. lalandii and 55% for R. porosus. Both species exhibit rapid growth, primarily in the first year of life. The growth estimates for R. lalandii and R. porosus are even faster than those reported in previous studies from tropical populations. This study estimated the age and growth parameters of two small coastal shark species for the first time in subtropical waters; unlike most sharks, both species exhibited very fast growth. Considering that these species are the most captured sharks in the study area, the results are crucial for fishery management and for the evaluation of the vulnerability status of the two species. [ABSTRACT FROM AUTHOR]

Sharks and rays caught by a small-scale fisheries in the western equatorial Atlantic Keywords: artisanal fisheries; Chondrichthyes; conservation; elasmobranch; endangered species EN artisanal fisheries Chondrichthyes conservation elasmobranch endangered species 830 833 4 12/21/20 20201201 NES 201201 INTRODUCTION The more than 1,100 known species of sharks and rays (Weigmann, 2016) are important trophic components of marine ecosystems. DISCUSSION This is the first study to use systematic monitoring of fisheries landings to describe the coastal fauna of elasmobranchs for the Ceará state and one of few for northeastern Brazil. The most captured and landed elasmobranch species at the Mucuripe embayment, I H. americanus i and I R. porosus i , are currently considered Data Deficient in Brazil (ICMBio, 2016). [Extracted from the article]

Age determination for stock assessments and conservation of cartilaginous fishes is mainly obtained by counting the annual growth bands in vertebrae. Recent studies show numerous inconsistencies and the need for systematic validation. We assessed the effectiveness of the fluorochrome alizarin red S, a common skeleton vital marker used as a time stamp for teleost fishes, on chondrichthyan. Twenty-five captive small-spotted catsharks (Scyliorhinus canicula) were marked by alizarin red S intraperitoneal injections. The fluorochrome produced a wide fluorescent mark on sectioned vertebral centra of all injected fish. Alizarin red S did not have a deleterious effect on growth during three months monitoring. The marks obtained remained stable in vivo for more than four years after injections and were resistant to fading during the observation under the microscope excitation light. Our results suggest that alizarin red S is an effective tool for long time vital marking of chondrichthyans. [ABSTRACT FROM AUTHOR]

A drone was used to study the richness and behaviour of scavengers attracted to the carcass of a sperm whale (Physeter microcephalus) in Seychelles, Western Indian Ocean. Over 30 sharks of 3 species (tiger shark Galeocerdo cuvier , bull shark Carcharhinus leucas and tawny nurse shark Nebrius ferrugineus) were recorded scavenging on the carcass. Tiger sharks dominated the scavenging, but with no evidence of agonistic behaviours or hierarchy, and may have facilitated scavenging by other species. Drone use allowed the analysis of such behaviours without observer influence, providing new insights into communal scavenging events. For the first time, multiple tiger, bull and nurse sharks were all recorded feeding on the same sperm whale carcass. Moreover, the event was observed using a drone, meaning that the sharks were undisturbed by humans and exhibited natural behaviour. Contrary to expectation, there was no aggression between any of the sharks. Instead, they all fed calmly alongside each other during this communal scavenging event. [ABSTRACT FROM AUTHOR]

This study aimed to characterize morphological aspects related to abortion through a non‐lethal approach in the shortnose guitarfish Zapteryx brevirostris, an endemic and threatened species commonly caught by artisanal fisheries. Two females with signs of abortion and one female exhibiting external signs of pregnancy were purchased alive at a fish market during the period when this species has developing embryos in southern Brazil. Scans were conducted using a portable ultrasound. Females with signs of abortion revealed an absence of embryos despite having a similar morphology of the uterus when compared to the pregnant female. Examination of the pregnant female revealed the presence of two embryos, measuring c. 100 mm, each detected through their midline. This study presents new data on uterine macromorphology following successive abortive events in a viviparous elasmobranch species and validates ultrasonography as a diagnostic tool for the species. Ultrasonography is an effective, non‐lethal and less‐invasive methodology that is recommended for use in future studies of abortion and other reproductive events in elasmobranchs. [ABSTRACT FROM AUTHOR]

The reproductive biology of Urotrygon microphthalmum was studied based on specimens caught as by-catch in shrimp ( Litopenaeus schmitti, Xiphopenaeus kroyeri, Farfantepenaeus subtilis and Farfantepenaeus brasiliensis) fishing operations between March 2010 and March 2012 on the coast of Pernambuco, Brazil. Females reached a larger total length ( LT) and total body mass ( MT) (298 mm and 148 g) than males (250 mm and 90 g). Length at maturity was estimated to be 188 and 199 mm LT for males and females. Uterine fecundity ranged from one to four embryos (mean ± s.d.: 1·85 ± 0·45). Size at birth was estimated to be 105 mm LT. Gestation lasted between 4 and 5 months. The reproductive cycle of U. microphthalmum is hypothesized to be asynchronous and biannual. [ABSTRACT FROM AUTHOR]

We report the first documented case of bicephaly in a chondrichthyan, the southern fiddler ray, Trygonorrhina dumerilii, in Australian waters. Females in the latter stages of pregnancy, as confirmed by ultrasound, were captured by hand in Swan Bay, Victoria (38.252°S, 144.616°E) in February 2013 and transported to aquaria. Up to 10 females gave birth in aquaria in early April 2013 to 11 neonates, one of which was a still-born, bicephalic neonate. Magnetic resonance imagery of the bicephalic neonate displayed the presence of two parallel vertebral columns running the entire length of the animal, diverging into two well formed heads. Morphological measurements were also made, comparing the bicephalic neonate to normal neonates. The cause of bicephaly is unknown, although congenital and environmental stressors during development may cause this condition. We present the first documented species of shark or ray in Australia to give birth to a two-headed offspring. Using magnetic resonance imagery (MRI), we found two parallel vertebral columns running the entire length of the offspring, diverging into two well formed heads. The cause of such births defects is unknown, although they may be linked to congenital and environmental stressors during embryonic development. [ABSTRACT FROM AUTHOR]

The stomach contents of the eyespot skate, Atlantoraja cyclophora (Regan, 1903), were examined with the goal to provide information about the diet of the species. Samples were collected off the southern coast of Rio de Janeiro, Brazil, near Ilha Grande, between January 2006 and August 2007, at a depth of about 60 m. The diet was analyzed by sex, maturity stages and quarterly to verify differences in the importance of food items. The latter were analyzed by: frequency of occurrence, percentage of weight and in the Alimentary Index. The trophic niche width was determined to assess the degree of specialization in the diet. Additionally, the degree of dietary overlap between males and females; juveniles and adults and periods of the year were defined. A total of 59 individuals of A. cyclophora were captured. Females and adults were more abundant. The quarters with the highest concentrations of individuals were in the summer of the Southern Hemisphere: Jan-Feb-Mar 06 and Jan-Feb-Mar 07. Prey items were classed into five main groups: Crustacea, Teleosts, Elasmobranchs, Polychaeta, and Nematoda. The most important groups in the diet of the eyespot skate were Crustacea and Teleosts. The crab Achelous spinicarpus (Stimpson, 1871) was the most important item. The value of the niche width was small, indicating that a few food items are important. The comparison of the diet between males and females and juveniles and adults indicates a significant overlap between the sexes and stages of maturity; and according to quarters, the importance of prey groups differed (crustaceans were more important in the quarters of the summer and teleost in Jul-Aug-Sep and Oct-Nov-Dec 06), indicating seasonal differences in diet composition. Three groups with similar diets were formed in the cluster analysis: (Jan-Feb-Mar 06 and 07); (Apr-May-Jun 06 and Jul-Aug-Sep 07); (Jul-Aug-Sep 06 and Oct-Nov-Dec 06). [ABSTRACT FROM AUTHOR]

The diet and diel feeding behaviour of the banded guitarfish Zapteryx xyster were examined along the Pacific coast of Costa Rica. A sample of 235 stomachs was collected between March 2010 and December 2011 as part of an ongoing shrimp-trawl by-catch monitoring programme. Samples from multiple day and night periods allowed testing the hypothesis that Z. xyster is more active at night, thus increasing the amount of food intake during night-time. Overall, shrimps (52·3% prey-specific index of relative importance, PSIRI i) and teleosts (27·2% PSIRI i) were the most important prey categories. Juveniles fed primarily on smaller shrimps ( Solenocera spp.), while adults shifted to larger prey. The amount of food consumed (as % of bodymass) by juvenile and adult Z. xyster increased significantly between 0400 and 1200 hours, while the proportion of empty stomachs decreased during the same time interval. These findings contradict the hypothesis that Z. xyster is more active and feeds at night. The study also revealed that Z. xyster, particularly juveniles, forage on several shrimp species and overlap spatially with the Costa Rican bottom-trawl fisheries. This has important management and conservation implications as Z. xyster may be experiencing high by-catch rates, and because of their life history is presumed to be vulnerable to intense levels of exploitation. [ABSTRACT FROM AUTHOR]

This study presents the second worldwide report on abnormal embryos of the sharpnose sharks, Rhizoprionodon, based on the two species (Rhizoprionodon porosus and Rhizoprionodon lalandii) occurring on the Brazilian coast. For R. porosus two conjoined twin embryos showing complete duplication of the vertebral column, viscera and several external structures (head, first and second dorsal fins, pectoral fins), and scoliosis in both axis at the pelvic fin level are reported. The three embryos of R. lalandii exhibited numerous lordosis and kyphosis along the entire vertebral column. The possible relationship between anomalies and the human major threats to sharks is discussed based on previous reproductive, genetic and ecotoxicological studies on R. lalandii for southern Brazil. [ABSTRACT FROM PUBLISHER]

Occurrence of abnormal rays reported in Indian waters was stumbled upon in the late 19th Century, but it was revised in the early 20th Century and in the past two decades. Reported morphological abnormalities for elasmobranchs in the Indian waters are restricted to pectorals that fail to unite with the sides of the head and fins that developed thick muscular segments. The occurrence of the malformed or adapted specimen Gymnura poecilura suggested reasons for adaptations or malformations. [ABSTRACT FROM AUTHOR]