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We describe here the morphological abnormalities found in six free-living specimens of Narcine vermiculata, N. sp., N. entemedor, and Pseudobatus leucorhynchus. Specimens were captured off the coast of the Gulf of Tehuantepec in November and December 2017 using bottom trawl nets and off the Ventanilla Lagoon from August 2023 to March 2024 using gillnets. We found abnormal disc width, pelvic fins, eyes, and spiracles in Narcine vermiculata; abnormal disc development in Narcine sp.; abnormal disc development, anophthalmia, and a spot on the liver in N. entemedor; and clasper absence, abnormal development of the disc and pelvic fins, and malformation of the vertebral column in Pseudobatos leucorhynchus. Based on the total batoid captures obtained during from 52 bottom trawls, we estimate that the probability of finding disc abnormalities (pectoral fins not fused or other types of abnormal development) was 1.0%, whereas anophthalmia occurred in 0.3% of specimens, and 0.2% of males did not have a clasper. The causes of these deformations need to be further investigated, in order to take appropriate actions to preserve the health of ecosystems and human beings. [ABSTRACT FROM AUTHOR]

The article discusses the discovery of active sound production in the wild Mediterranean blonde ray Raja brachyura, a type of elasmobranch. The sound produced by the blonde ray consists of a series of high-pitched pulses and is similar to sounds produced by other elasmobranch species. This finding sheds light on the communication and behavioral aspects of elasmobranchs, highlighting the importance of further research in this area. [Extracted from the article]

Patterns of mother–embryo fractionation of 13C and 15N were assessed for their predictability across three species of batoids caught as by‐catch in south‐eastern Australia. Stable isotope analysis of 24 mothers and their litters revealed that isotope ratios of embryos were significantly different from their corresponding mothers and that the scale and direction of the difference varied within and across species. The range of variation across species was 3.5‰ for δ13C and 4‰ for δ15N, equivalent to a difference in trophic level. In one species (Urolophus paucimaculatus) litters could be significantly enriched or depleted in 13C and 15N relative to their mothers' isotope signatures. These results suggest that patterns of mother–embryo isotope fractionation vary within and between species and that these patterns may not be explained only by developmental mode. Contrasting patterns of fractionation between and within species make it difficult to adjust mother–embryo fractionation with broad‐scale correction factors. [ABSTRACT FROM AUTHOR]

Context. The extinction risk of sharks and rays exceeds that of most other vertebrates. Genetic analyses can help identify conservation risks. Aims. Identification of Fiji's maskray and testing the null hypothesis of no genetic differentiation within the species over time. Methods. Mitochondrial DNA cytochrome oxidase subunit 1 (COI) barcoding was used for species identification, and DArTseq technology to monitor the genetic diversity. Cohort samples were collected in 2015 and 2022. A subset from each cohort was barcoded. The genetic survey was complemented by a size comparison between the two cohorts. Key results. Barcoding of the COI gene showed a maximum similarity of 97.84% to Kuhl's maskray (Neotrygon kuhlii) and 96.83% to the Coral Sea maskray (Neotrygon trigonoides), but no higher-level distinct species match to reference sequences in the Barcode of Life Datasystem. Genotyping of 56 individuals in two cohorts yielded 21,293 single nucleotide polymorphisms (SNPs), and 3871 SNPs per individual were retained. The neutral genetic diversity remained stable over time. The 2015 cohort showed positive inbreeding, with one full-sibling pair identified in each cohort. Body size comparisons indicated a significant reduction in disc length and width in the 2022 cohort. Conclusions. The smaller body size of the 2022 cohort may hint at increased fishing pressure, but genetic diversity has not been affected. Thus, the null hypothesis is accepted. Implications. These findings provide insights into the genetic diversity of Fiji's maskray and enable a genetic comparison with current Neotrygon species known in the region. Taxonomy confirmation is needed, but the presence of a cryptic or potentially new maskray in Fiji seems plausible. [ABSTRACT FROM AUTHOR]

This paper presents information on the morphological, morphometric, and dental sex differences in the dwarf round ray Urotrygon nana. We recorded 12 morphological traits, sex, the distribution pattern of dermal denticles, the number of tooth rows, and the tooth shape of 466 individuals. The disc width of females ranged from 50 to 172 mm and that of males ranged from 53 to 135 mm. A neuronal classification model and a correspondence analysis showed that female disc width was 21.5% broader, and the distance from the rostrum to the anus was 17.7% longer than that of males, whereas males presented 19.5% greater distance between the nostrils, 9.7% greater preorbital snout length, 6.8% greater cloaca to caudal‐fin length, 2.7% greater interorbital distance, and 1.1% greater total length than females. The disc of adult males, including the abdominal cavity area, was densely covered with dermal denticles, which were slightly larger than those observed in females. Females presented homodont dentition with molariform teeth and a smooth lozenge‐shaped crown with rounded margins. Males exhibited homodonty but with tooth morphology variations in individuals of different sizes (from molariforms to sharper cusp teeth). There were changes in disc shape (from subcircular to oval), distribution and size of dermal denticles (more abundant and larger), and tooth shape (from molariform to monocuspid teeth) during male development, from neonates to adults. U. nana exhibited sexual dimorphism in size, disc shape, number and shape of teeth, and distribution and size of dermal denticles. [ABSTRACT FROM AUTHOR]

The spotted eagle ray Aetobatus ocellatus (Kuhl, 1923) has a widespread Indo-West Pacific distribution and displays substantial population genetic structuring. Genetic data are crucial for understanding the species' diversity, connectivity, and adaptation. However, molecular genetic information on A. ocellatus from Melanesia is lacking, which impedes our understanding of gene flow among geographic regions. In this study, we sampled 45 A. ocellatus, primarily from Fiji's largest fish market in the capital, Suva. Mitochondrial DNA Cytochrome C Oxidase subunit I (COI) barcoding was used for species identification, and DArT-seqTM technology was applied to assess the nuclear genetic diversity. Barcoding of the COI gene showed a 98.6% to 99.8% similarity to A. ocellatus reference sequences in the Barcode of Life Data System, and the 45 individuals were represented by three major evolutionary haplotype clusters. Genotyping resulted in 24,313 Single-Nucleotide Polymorphisms (SNPs) which were quality-filtered to 7094 SNPs per individual. The observed heterozygosity level was 0.310. The inbreeding coefficient was positive, and genotyping identified one full-sibling pair and one half-sibling pair from the 45 individuals. Additionally, eagle rays exhibit polychromatic patterns, and at least three ventral pattern variations were recorded in specimens from the market. Collectively, our main findings characterize the genetic profile of A. ocellatus in Fiji and can help to understand the diversification of this species within the region. [ABSTRACT FROM AUTHOR]

Despite the high diversity of elasmobranch fishes in the Balearic Islands, knowledge of their biology and population dynamics is still scarce. A recent mark-and-recapture experiment off the Balearic Islands tagged 3738 individuals of 23 shark and batoid species during MEDITS and CANAL bottom trawl scientific surveys from June 2021 to August 2023. Retrieval was reported for the sharks Scyliorhinus canicula and Mustelus mustelus, revealing relatively small home ranges for these species (0.2–38.5 km and 7.8–15.3 km for S. canicula and M. mustelus, respectively). Recapture efficiency was higher from scientific surveys than from commercial catches, highlighting potential challenges in collaboration with fishermen and recapture reports. Density estimates obtained from the MEDITS bottom trawl survey suggest a much larger population for S. canicula than estimates from the mark–recapture data, indicating MEDITS density estimates for this species may be overestimated due to its scavenger behavior perhaps favoring individuals searching for discards aggregated in the fishing grounds. This study emphasizes the importance of monitoring, collaborative efforts, and improved reporting mechanisms to enhance our understanding of elasmobranch populations and provide support for sustainable management of these vulnerable marine species. [ABSTRACT FROM AUTHOR]

Data on the reproductive biology of elasmobranchs are essential for understanding their life history. Published studies on batoid ray reproductive biology are comparatively scarce, leading to limited understanding and data gaps. The Oceania fantail ray, Taeniura lessoni, is a good example. This Data Deficient nearshore stingray is restricted to Melanesia, with lacking biological and ecological data, including reproduction. To expand upon the limited life-history data for this species, this short paper provides observational data on the reproductive condition in female T. lessoni, at Drawaqa Island, Fiji. Field work involved direct observations and ocean temperature measurements. Over 40 days spanning three months, 105 surveys were conducted across five sites, resulting in 71 sightings of the species. Based on spot patterns and body markings, four female individuals were identified. Between January and March 2024, these females exhibited convex dorsa indicating advanced gestation, transitioning to concave dorsa suggesting parturition. The presence of neonates from early March onwards coincided with the estimated parturition period inferred from the rays' condition. Furthermore, a female previously pregnant was photographed with a dermal abrasion around her pectoral fin, possibly indicating pre-copulatory biting, suggesting a continuous reproductive cycle. The average monthly water temperature at the surveyed sites remained relatively stable throughout the study. Collectively, our findings suggest that Drawaqa Island provides suitable habitat niches for reproductive activities in female T. lessoni. Repeated and long-term data is certainly needed to confirm either a continuous reproductive cycle or seasonal peaks. While preliminary, our observational data represents the first documentation on female reproductive condition in a stingray in Fiji. [ABSTRACT FROM AUTHOR]

Global concern over the overfishing of elasmobranches is well known, with an increasing number of studies in various regions of the world. The Gulf of Oman, like other ecosystems, the increasing fishing fleet and fisheries are considered important factors affecting aquatic resources. This study aimed to assess CPUA and biomass of batoidfishes and also biomass variation in the Gulf of Oman during two last decades. Sampling was carried from October to January using research bottom trawler of “FERDOWS1”, into 8 strata from Bandar Abbas (strata J) to marine border of Pakistan (strata Q). Overall, 1743 samples of batoidfishes belonging to 15 species and 10 families were recorded. The results appeared minimum and maximum CPUA in strata L and P with 1651.5 and 34.7 kg, respectively. Also, minimum and maximum biomass were found in strata L (1341.7 tonnes) and N (16.1 tonnes). Examining the trend of changes in CPUA and biomass from 2004 to 2017 showed that, with the exception of strata L, there were decreasing trend in all other strata. The results of the present study make it clear that after the apex predators, the meso-predators are also under threat, and the future of the Gulf of Oman ecosystem and the stability of the food web require proper management for the sustainable preservation of resources of the food web. [ABSTRACT FROM AUTHOR]

Chondrichthyans are a very important taxon that plays a top predator role in the trophic level of the food web, and species are particularly vulnerable to exploitation in the marine ecosystem. The deep waters of the eastern Mediterranean Sea have been less studied than the continental shelf, especially for the chondrichthyans. Therefore, the present study was conducted to investigate the spatio-temporal distribution of chondrichthyans collected monthly in eight different (200–900 m) depth strata during different periods (2010–2011 and 2019–2021) using an otter bottom trawl. A total of 17 species were identified in upper bathyal, composed of 6 batoids, 10 sharks, and one chimaera. The constant species (dominance: DO% > 50) in the study area were Galeus melastomus, Scyliorhinus canicula, Etmopterus spinax, and Raja clavata. The most abundant species was E. spinax, followed by G. melastomus. Fourteen and 15 species were caught during the first and the second survey, respectively. Biodiversity characteristics (number of species, abundance, and diversity indices) varied only with bottom depth. Two different depthwise assemblages were estimated along the bottom depth gradient; ≤ 500 m and > 500 m. The discriminator species were R. clavata, S. canicula, G. melastomus, Dipturus oxyrinchus, and Squalus blainville found on the upper slope and E. spinax, G. melastomus, and Centrophorus cf. uyato found on the lower slope. With our results, total number of demersal chondrichthyan species found in the bottom (bathyal and continental shelf) of Antalya Bay was reached to 26 species. [ABSTRACT FROM AUTHOR]

Migration is a critical aspect of ocean ecosystems, and understanding this phenomenon answers ecological and management questions. Given the difficulty in tracking ocean animals across large distances, the extent to which different ray species perform long‐distance movements, such as migrations, remains unknown. This study used passive acoustic telemetry to track the movements of endemic diamond Gymnura natalensis and critically endangered duckbill Aetomylaeus bovinus rays along the South African coastline using a collaborative nationwide network of coastal acoustic receivers for up to 7 years. Duckbill rays were detected significantly more frequently than diamond rays, but both species moved between the south and east coasts of South Africa (traveling up to 1167 km). Tagged individuals were detected significantly more often in their tagging locations during summer months but traveled significantly further distances during winter months. Furthermore, movement models fitted to individual duckbill rays' annual net‐squared displacement identified most individual annual movements as migratory. This evidence suggests that both diamond and duckbill rays make eastward winter migrations and return to specific areas along the coastline during the summer months. The exceptions to this were diamond rays tagged on the east coast that were not found to migrate seasonally, which supports previous research that there is intraspecific variability in migrations for ray species. These findings have implications for understanding ray migration not only on a global scale but also locally for spatial management interventions and population delineation. [ABSTRACT FROM AUTHOR]

Data on the reproductive biology of elasmobranchs are essential for understanding their life history. Published studies on batoid ray reproductive biology are comparatively scarce, leading to limited understanding and data gaps. The Oceania fantail ray, Taeniura lessoni, is a good example. This Data Deficient nearshore stingray is restricted to Melanesia, with lacking biological and ecological data, including reproduction. To expand upon the limited life-history data for this species, this short paper provides observational data on the reproductive condition in female T. lessoni, at Drawaqa Island, Fiji. Field work involved direct observations and ocean temperature measurements. Over 40 days spanning three months, 105 surveys were conducted across five sites, resulting in 71 sightings of the species. Based on spot patterns and body markings, four female individuals were identified. Between January and March 2024, these females exhibited convex dorsa indicating advanced gestation, transitioning to concave dorsa suggesting parturition. The presence of neonates from early March onwards coincided with the estimated parturition period inferred from the rays' condition. Furthermore, a female previously pregnant was photographed with a dermal abrasion around her pectoral fin, possibly indicating pre-copulatory biting, suggesting a continuous reproductive cycle. The average monthly water temperature at the surveyed sites remained relatively stable throughout the study. Collectively, our findings suggest that Drawaqa Island provides suitable habitat niches for reproductive activities in female T. lessoni. Repeated and long-term data is certainly needed to confirm either a continuous reproductive cycle or seasonal peaks. While preliminary, our observational data represents the first documentation on female reproductive condition in a stingray in Fiji.

Simple Summary: Poor quality of biological information, such as age and growth parameters, could be a source of variability with a significant impact on stock assessment results. Concerning the ageing process, variability is frequently linked to differences in the interpretation of calcified structures. The evaluation of precision and accuracy therefore represents a keystone in the ageing procedure. The intercalibration of age readings represents a crucial step in the ageing procedure; the use of different sampling methods, structures, preparation techniques, and ageing criteria can significantly affect age and growth data. This study evaluated the precision and accuracy of ageing for the most important North Atlantic (NA) and Mediterranean (M) ray species, Raja clavata, Raja brachyura, Torpedo marmorata, and Dipturus oxyrinchus, through exchange exercises carried out by readers from different laboratories. In addition, growth parameters were estimated from the obtained data. A total of 663 individual batoids were analysed. R. clavata and R. brachyura samples were obtained from both the NA and the M, while vertebral centra of T. marmorata and D. oxyrinchus were only available for the M. High reading variability was observed for all four evaluated species in terms of CV, APE, and PA. D. oxyrinchus and T. marmorata showed relatively slow growth and the von Bertalanffy model with fixed t0 and Gompertz's model were, respectively, the most precise models for each of these species. In R. brachyura, females had a faster growth rate compared to combined sexes. The vbt0p proved the most precise model for describing growth in this species, and no statistical differences were found between the NO and the M. For R. clavata, the best-fitting model was the vbt0p for females and males in the NO and for females from the M, while the best-fitting model for males from the M and sexes combined for both areas was log.p. Distinct growth patterns were observed between the two study areas. [ABSTRACT FROM AUTHOR]

Ivanovcestus yakiae gen. et sp. nov. was collected from specimens of the batoid Sympterygia bonapartii from waters off Río Negro and Buenos Aires Provinces, in the Argentine Sea. Ivanovcestus gen. nov. is assigned to the Rhinebothriidea for their possession of facially loculated bothridia borne on stalks and a cirrus covered by spinitriches. The new genus is unique in the arrangement of loculi and septa on the distal bothridial surface. The molecular analysis based on 18S and 28S rDNA of two specimens of the new species identified Ivanovcestus gen. nov. as a member of the family Escherbothriidae, with our study representing the first record of this family in the Argentine Sea. The proposed new genus requires a new amended diagnosis for the Escherbothriidae, to include a new pattern of loculi and septa for the distal bothridial surface, as well as a new host. In addition, the present study proposes to transfer two species of Rhinebothrium , originally described parasitizing the skate Sympterygia lima in the Chilean Sea (i.e., Rhinebothrium chilensis and Rhinebothrium leiblei), to Ivanovcestus gen. nov. Examination of the original descriptions and type material revealed several morphological characters that justify the relocation of both species to the new genus. [ABSTRACT FROM AUTHOR]

Although historically widespread in most of the shallow and warm waters of the world, the presence of sawfishes in the Mediterranean Sea is still a debated question. For some authors, they never inhabited this basin except as vagrants, while for other authors both Pristis pristis and Pristis pectinata were present in the Mediterranean Sea but were extirpated in the 1960s-1970s. The sawfish rostrum kept in the Basilica Santuario del Carmine Maggiore (Naples, Italy), and considered by some authors the first record of sawfish in the Mediterranean was studied using a combination of morphological, genetic, radiocarbon dating and histochemical staining methods to validate the taxonomic identification, estimate its age and assess its geographical origin. Results indicate that the rostrum does not belong to P. pristis as reported by previous authors, but instead possesses morphological and genetic characters typical of P. pectinata. In addition, the radiocarbon age shows that the rostrum is more recent than previously believed, dating it back to the mid-nineteenth century, and genetic and meristic results cast doubt on its presumed Mediterranean origin. This study demonstrates that historical records should always be critically evaluated before using them to draw any far-reaching conclusion about species' past ecology and/or biogeography, and that future studies using historical information and specimens should adopt an integrative taxonomy approach similar to the one used here. [ABSTRACT FROM AUTHOR]

Urobatis jamaicensis is a coastal batoid species affected by habitat loss and small‐scale exploitation from fisheries and the aquarium trade, yet the life‐history information available is limited. This is the first study to assess the vertebral centra from 195 stingrays to estimate age and growth patterns, and compare them with the biannual reproductive pattern previously reported for this species. Age‐at‐size data were compared using five different growth models and found a two‐parameter von Bertalanffy growth function (VBGF), the Gompertz model and a modified VBGF fit best for males, females and sexes combined, respectively. Maturity was achieved before 1 year. However, growth did not cease with the onset of maturity, but instead slowed down. Results from marginal increment analysis and edge analysis indicated a nonannual somatic growth pattern with influences from the biannual reproduction cycle where peaks in resource allocation may be focused on ovulation rather than growth during March when larger brood sizes are present, while resources may be allocated more towards growth during August and September when brood sizes are generally smaller. These results may be used as a proxy for species with similar reproductive patterns or for those that lack annual or seasonal growth patterns. [ABSTRACT FROM AUTHOR]

Elasmobranchs are declining worldwide due to overfishing. In developing countries and island states in tropical regions, small-scale and recreational fisheries can significantly impact the dynamics of neritic species. We investigated elasmobranch diversity at Reunion Island, a marine biodiversity hotspot in the Western Indian Ocean. Combining information from the literature, catches from the local shark control program, results from a survey of local recreational fishing, and through barcoding of some specimens, we updated the list of elasmobranchs to 65 species. However, uncertainties remain about the actual presence of some species, such as the three sawfish species. Results highlight the disappearance of most coral reef-associated species, as already suspected. Results also suggest that local populations of scalloped hammerhead shark (Sphyrna lewini) and bottlenose wedgefish (Rhynchobatus australiae) seem healthy, in contrast with their decline in the region. For some species, such as bull sharks (Carcharhinus leucas) and scalloped hammerhead sharks, Reunion Island is a site of reproduction, and as such, the species are exploited at both juvenile and adult stages, which likely increases their vulnerability. In the context of global elasmobranch decline, it is urgent to clarify the conservation status and evaluate the degree of isolation of local populations to identify research and conservation priorities. [ABSTRACT FROM AUTHOR]

A parasite-host list of cestodes parasitizing chondrichthyans in the Southwest Atlantic off Argentina and surrounding waters of Antarctica is compiled based on the available literature. The list is based on published descriptions and redescriptions of species, and newly collected worms during the current study. A total of 57 valid species belonging to 28 genera of the orders Cathetocephalidea, Diphyllidea, Gyrocotylidea, Lecanicephalidea, Onchoproteocephalidea, Phyllobothriidea, Rhinebothriidea, "Tetraphyllidea", and Trypanorhyncha is listed. Information on hosts, localities, specimens in collections and comments on tapeworms are also included. A host-parasite list including chimaeras (1 order, 1 genus), batoids (4 orders, 10 genera), and sharks (3 orders, 5 genera) is provided. Tapeworm diversity, distribution range, and host associations are discussed. The cestodes orders Phyllobothriidea and Rhinebothriidea exhibit the highest species richness, with 13 and 12 species, respectively. Onchoproteocephalideans and rhinebothriideans have the broadest geographic distribution in the study area. Regarding hosts, arhynchobatid skates are the group most frequently associated with cestodes. However, further collecting efforts are necessary to understand whether this data reflect the real diversity and host association of these parasites or is a result of a bias in sampling. [ABSTRACT FROM AUTHOR]

Species belonging to the superorder Batoidea have been poorly assessed due to the lack of information on their life history aspects and their limited economic value. This work presents an overview of skates and rays inhabiting the marine Greek waters and reports biodiversity issues requiring resolution for conservation purposes. Overall, 30 species from nine families and 16 genera have been documented within the past 22 years, based on the available literature and technical reports from research surveys of the Hellenic Centre for Marine Research (HCMR). However, 28 species are currently confirmed, since the presence of two rajids has not been sufficiently demonstrated and hence is considered as doubtful. Recent changes in nomenclature allowed us to replace old with new names in four species on the Greek list; patterns in the frequency of occurrence were observed and species were assigned into five categories; and diversity and misidentification issues were reported by family. Although Greek waters are oligotrophic and not considered a biodiversity hot spot for elasmobranchs, a high number of batoid species is documented in the area; therefore, the need to reinforce knowledge on biological aspects of skates and rays, define their status and identify their main threats is essential. [ABSTRACT FROM AUTHOR]

The Neogene of Kutch, India is well known for its rich marine and terrestrial vertebrate assemblages. However, the data of piscean fauna from the middle Miocene of India is very scarce. We report here additional chondrichthyan and osteichthyan remains from the middle Miocene deposit of Chhasra Formation, Palasava site, Kutch, Gujarat, India. The elasmobranchs include Carcharhinus Blainville, 1816 (C. brevipinna (Müller & Henle, 1839), C. falciformis (Müller & Henle, 1839), C. cf. leucas, C. aff. perezi, Carcharhinus sp.), Negaprion Whitley, 1940 (Negaprion sp.), Aetobatus Blainville, 1816 (Aetobatus sp.), Myliobatis Cuvier, 1816 (Myliobatis sp.), Dasyatis Rafinesque, 1810 (D. probsti Cappetta, 1970, D. rugosa Probst, 1877), Himantura Müller & Henle, 1837 (H. menoni Sahni & Mehrotra, 1981), Pastinachus Rüppell, 1829 (Pastinachus sp.), and Taeniurops Garman, 1913 (Taeniurops sp.). The teleosts of Palasava are represented by four families including Bagridae Bleeker, 1858, Channidae Fowler, 1934, Characidae Latreille, 1925 and Cyprinidae Cuvier, 1817. Sørensen-Dice coefficient data of Palasava elasmobranchs show a good similarity index with their counterparts in the Mediterranean Sea suggesting the existence of short-lived reopening of the marine pathway. However, a much higher faunal affinity with those of Eastern Pacific indicates a gradual shift in migration path through the Pacific Ocean to Indo-Pacific region after the permanent landbridge was formed. The vertebrate fauna from the Palasava suggests a coastal, marginal marine, near-shore littoral to neritic environment of deposition with the influence of freshwater riverine system. The integration of the floras and faunas from Palasava locality indicates the presence of warm, humid/ wet, tropical to sub-tropical environmental conditions during the middle Miocene. [ABSTRACT FROM AUTHOR]

Arsenic (As) concentrations were measured in the muscle and liver of the speckled guitarfish Pseudobatos glaucostigmus and its main prey Penaeus californiensis, in Santa Rosalia, western Gulf of California, to determine bioaccumulation and biomagnification. Higher mean wet weight (w.w.) values were found in muscle tissue (9.87 μg g -1 ) compared to liver tissue (5.32 μg g -1 ); however, the highest concentrations were found in the liver (48.05 μg g -1 ). All samples showed As concentrations above the maximum permissible limit for human consumption. The highest concentrations in mature females (muscle: 6.93 μg g -1 ; liver: 14.5 μg g -1 ) concerning pregnant females (muscle: 5.01 μg g -1 ; liver: 8.46 μg g -1 ) may indicate a maternal transfer of As from mothers to their embryos. Arsenic bioaccumulates in the liver, which was evident from the positive correlation between total length and As concentration. Arsenic levels in Penaeus californiensis showed biomagnification from prey to predator for both tissues., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Narcine entemedor and Rhinoptera steindachneri are 2 viviparous batoid species of commercial importance on the Pacific coast of Mexico. However, no adequate management plan has been set forth for either of them to ensure sustainable use. The aims of this study were to assess the reproductive potential and the potential rate of population increase (rʹ) of both species, as well contrasting their reproductive strategies, to infer how susceptible they are to fishing exploitation. Comparatively, among batoids, N. entemedor females have an early age at maturity, relatively high fecundity, and an intermediate lifespan, while R. steindachneri females have an early age at maturity, low fecundity, and a relatively short lifespan. According to our estimates, however, both species have relatively high reproductive potential, which N. entemedor exhibits by investing energy in maximizing fecundity and R. steindachneri by increasing the embryo’s body mass. Therefore, N. entemedor has better capacity to recover from relatively high overfishing (rʹ = 0.48) in comparison with R. steindachneri (rʹ = –0.18). The methodology used in this study proved to be a good option to assess the risk of overfishing in species for which there is limited data.

Elasmobranchs provide greatly relevant ecosystem services for the balance of the environments in which they are inserted. In recent decades, sharp population declines have been reported for many species in different regions worldwide, making this taxonomic group currently one of the most threatened with extinction. This scenario is almost entirely due to excessive fishing pressure, but any contributing factor that may cause additional mortality to populations must be mapped and monitored. In a fast-changing world, emerging marine pollution associated with climate change display the potential to increase the spread of infectious agents. These can, in turn, lead to mortality events, both directly and indirectly, by reducing immune responses and the physical and nutritional condition of affected individuals. In this context, the present study aimed to analyze data concerning elasmobranch-associated microbiota, identifying study trends and knowledge gaps in order to direct future studies on this topic of growing relevance for the health of wild populations, as well as individuals maintained in captivity, considering the zoonotic potential of these microorganisms. [ABSTRACT FROM AUTHOR]

The Călata site (north-west of Transilvanian Basin, Romania) includes the Ciuleni Member of the middle Eocene-age Mortănușa Formation, a marine deposit in an outer, open marine facies, from where fossil vertebrates were very poorly known. In the last four years, nearly 150 remains of fish (mostly teeth) were recovered from the Călata site. We identified 21 taxa representing 20 genera that belong to 12 orders of chondrichthys and teleostei fishes. This study is the first to report Rostroraja and Palaeocybium from Romania, and we report seven additional genera from the Bartonian of Romania for the first time. We performed analysis of calcareous nannoplankton and foraminifera which allowed us to refine the age of the deposits and corroborate palaeoecological data. The combined data from the microfossils and fishes document the first middle-late Bartonian (NP17) marine fish fauna from Romania. This fauna was deposited in tropical waters with relatively shallow depths and with increased terrigenous input from a probable close-by shoreline. [ABSTRACT FROM AUTHOR]

Climate change stressors (e.g., warming and ocean acidification) are an imminent challenge to the physiological performance of marine organisms. Several studies spanning the last decade have reported widespread effects of warming and acidification on marine fishes, especially teleosts, but more work is needed to elucidate the responses in marine elasmobranchs, i.e., sharks and rays. Dispersal capacity, as a result of locomotor performance, is a crucial trait that will determine which group of elasmobranchs will be more or less vulnerable to changes in the environment. In fact, efficient and high locomotor performance may determine the capacity for elasmobranchs to relocate to a more favorable area. In this review we integrate findings from work on locomotion of marine sharks and rays to identify characteristics that outline potential vulnerabilities and strength of sharks and rays under climate change. Traits such as intraspecific variability in response to climatic stressors, wide geographic range, thermotaxis, fast swimming or low energetic costs of locomotion are likely to enhance the capacity to disperse. Future studies may focus on understanding the interacting effect of climatic stressors on morphology, biomechanics and energetics of steady and unsteady swimming, across ontogeny and species. [ABSTRACT FROM AUTHOR]

Elasmobranchs provide greatly relevant ecosystem services for the balance of the environments in which they are inserted. In recent decades, sharp population declines have been reported for many species in different regions worldwide, making this taxonomic group currently one of the most threatened with extinction. This scenario is almost entirely due to excessive fishing pressure, but any contributing factor that may cause additional mortality to populations must be mapped and monitored. In a fast-changing world, emerging marine pollution associated with climate change display the potential to increase the spread of infectious agents. These can, in turn, lead to mortality events, both directly and indirectly, by reducing immune responses and the physical and nutritional condition of affected individuals. In this context, the present study aimed to analyze data concerning elasmobranch-associated microbiota, identifying study trends and knowledge gaps in order to direct future studies on this topic of growing relevance for the health of wild populations, as well as individuals maintained in captivity, considering the zoonotic potential of these microorganisms.

Context: Rhinoptera steindachneri is the third-most abundant batoid species in the artisanal gillnet fishery of the Gulf of California, but there are limited age and growth data available for management. Aims: The aim was to estimate age and growth of this species from vertebral centra of 276 individuals. Methods: Two adjusted data sets were constructed on the basis of the birth and capture months and defining adequately the birth band. Individual growth was described through a multi-model approach and inference by using von Bertalanffy, Gompertz, and Logistic models (two and three parameters), and a two-phase growth model (four and five parameters). Key results: The model with the best fit to the size-at-age data was the two-phase model for both sexes (females: Dw∞ = 91.21 cm; k = 0.25 year−1, Dw0 = 46.2 cm; males: Dw∞ = 79.1 cm; k = 0.42 year−1, Dw0 = 45.5 cm). Maximum ages ranged from 9.92 to 10.75 years (female) and from 6.92 to 7.67 years (males). Maturity age was estimated in 3.92 years (females) and 3.72 years (males). Conclusions: Rhinoptera steindachneri is a batoid species with intermediate growth and a shorter lifespan than for confamilial species and even than species with similar reproductive traits. Implications: The need to carry out age validation studies for this species is highlighted. The age and growth of the Pacific cownose ray, Rhinoptera steindachneri , were examined in the south-western region of the Gulf of California, through edge type and marginal increment analysis of 276 vertebral centra. Individual growth was described using a multi-model approach and inference. Results indicated that R. steindachneri is a batoid species with intermediate growth and a shorter lifespan than for confamilial species and even than species with similar reproductive traits. [ABSTRACT FROM AUTHOR]

Peru presents an important habitat and fishery area for mobulid rays in the Eastern Pacific in which five mobulid species interact with fisheries. Yet, management is weak and species-specific fishery information is limited for this group. Therefore, this study describes species, body size, and sex composition of mobulid rays caught by small-scale fisheries in northern Peru at four landing points. Between December 2013 and May 2014, four mobulid species were recorded at the landing points: Mobula mobular, Mobula munkiana, Mobula thurstoni, Mobula tarapacana. A total of 270 individuals were identified and measured: Ninety-six percent of mobulids were M. mobular. The mean body size, for M. mobular, was 164 ± 37 cm disc width with a 1:1 sex ratio; therefore, 82% of individuals sampled in this study were sexually immature. Furthermore, the information presented here is useful for identifying nursery areas for M. mobular. These results improve the fishery information on mobulid rays by providing information that can assist decision makers and stakeholders on prioritizing research and management effort to M. mobular. Mobulid rays are globally one of most threatened elasmobranch groups; thus, this research aids in the conservation of key habitats. [ABSTRACT FROM AUTHOR]

The skeleton of the batoid fish consists of a mixture of calcified and uncalcified cartilage with a typical layout of mineral deposition toward the outer border, leaving an uncalcified central core in most of the skeleton segments. An exception is observed in the radials, where mineral deposition is central. Joints and endoskeleton segments were studied in two adult samples of Raja cf. polystigma. Histomorphology, mineral deposition pattern, and zonal chondrocyte duplication activity were compared among several endoskeleton segments, but with particular attention to the fin rays; in the first, the uncalcified cartilage is central with an outer layer ranging from mineralized tesserae to a continuous calcified coating, whereas in the second, the uncalcified cartilage surrounds one or more central calcified columns. The diarthroses have a joint cavity closed by a fibrous capsule and the sliding surfaces rest on the base of mineralized tesserae, whereas the interradial amphiarthroses show a layer of densely packed chondrocytes between the flat, calcified discs forming the base of neighboring radials. In the endoskeleton segments, three types of tesserae are distinguished, characterizing the phases of skeletal growth and mineralization which present differences in each endoskeleton segment. The chondrocyte density between central core, subtesseral layer, and radial external cartilage did not show significant differences, while there was a significant difference in chondrocyte density between the latter zones and the type c tesserae of the pelvic girdle. The histomorphology and morphometry observed in Raja cf. polystigma suggest a model of cartilage growth associated with structural stiffening without remodeling. A key point of this model is suggested to be the incomplete mineralization of the tesseral layer and the continuous growth of cartilage, both enabling fluid diffusion through the matrix fibril network of scattered, uncalcified cartilage zones inside and between the tesserae. [ABSTRACT FROM AUTHOR]

Within the eastern Mediterranean, increased fishing pressure coupled with a lack of basic biological information is threatening the sustainability of the rare Lusitanian cownose ray (Rhinoptera marginata). To provide baseline life-history data for this species, age estimates were obtained from vertebral band counts of 224 rays (size range: 210–998 mm disc width and 140 to 13,600 g weight) collected from Iskenderun Bay. Females ranged in size from 210 to 998 mm disc width and 238 to 13,600 g weight, while males ranged from 130 to 866 mm disc width and 140 to 8250 g weight. The index of average percent error (2.8%) and age-bias plot suggest that the aging method used represents a precise and non-biased approach. Marginal increment analysis indicated that a single opaque band is deposited annually between August and September. The oldest ages obtained for R. marginata were 9 years for males and 19 years for females, which corresponded to total lengths of 866 and 998 mm disc width, respectively. For males, limited samples prevented the accurate calculation of growth rates; however, for combined sexes, observed and disc width-at-age data resulted in the following von Bertalanffy growth parameters: DW∞ = 1102.16 mm, k = 0.148 and t0 = −0.2167. Although additional samples are necessary to determine growth rates in males, the results of the present study indicate that R. marginata females exhibit life history characteristics similar to other Rhinoptera species. [ABSTRACT FROM AUTHOR]

Nursery areas are crucial for many elasmobranch species, providing advantages such as increased access to prey and reduced predation risk. This study investigated the trophic interactions of two juvenile stingray species within a coastal communal nursery using stable isotope analysis. Muscle, plasma and red blood cells samples were taken from the mangrove whipray Urogymnus granulatus and the cowtail stingray Pastinachus ater, and δ15N, δ13C and δ34S measured. Urogymnus granulatus had higher mean δ13C, δ15N and δ34S than P. ater. General linear models showed no significant trends between δ13C, δ15N or δ34S and body size or sex. Low isotopic niche overlap, combined with previous data on movement patterns, provided evidence of niche partitioning between stingrays that likely reflect differences in feeding grounds and prey selection. Despite the differences in feeding grounds and prey selection, previous studies showed that U. granulatus and P. ater share sand and reef flat areas for most of the day (~20 h). δ13C and δ34S values suggested that mangrove-derived carbon had little importance to stingrays' diets in the study area. Results presented in this study bring new insights to the feeding ecology of two sympatric stingray species and their trophic interactions within a communal nursery area. [ABSTRACT FROM AUTHOR]

Copyright of Revista de Biologia Marina y Oceanografía (RBMO) is the property of Universidad de Valparaiso, Facultad de Ciencias del Mar 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.)

Length-weight relationships (LWR) were estimated for four species of batoids, Zapteryx xyster, Rostroraja equatorialis, Pseudobatos leucorhynchus and Gymnura crebripunctata, collected in Ecuadorian waters. Values of the allometric growth parameter (b) oscillated from 2.41 to 3.15. Pseudobatos leucorhynchus and G. crebripunctata exhibited isometric type growth, while Z. xyster and R. equatorialis showed negative and positive allometric growth, respectively. New records of minimum sizes were obtained for free-swimming R. equatorialis (7.8 cm TL) and G. crebripunctata (20.0 cm DW). Data obtained constitute a baseline for future management and conservation studies. [ABSTRACT FROM AUTHOR]

Although morphological abnormalities in several rays and skate species around the American continents have frequently mentioned, their numbers are unknown. The present work record morphological abnormalities in four Urotrygonidae species. Two anophthalmic specimens were detected (Urotrygon microphthalmum and Urobatis halleri). Two individuals lacked caudal fins (Urobatis maculatus and Urotrygon chilensis). Two round rays showed incomplete fusion of the pectoral fin to the head (U. microphthalmum and U. chilensis). Vertebral compression and fusion were found in a 6‐year‐old female Urotrygon rogersi. In addition, 118 abnormal batomorph specimens were gathered from the available bibliography, spanning the last six decades (1959–2021). Amblyraja doellojuradoi was the species with the highest number of abnormalities (18). The most common anomaly was an incomplete fusion of the pectoral fin with the head. Since 2010, at least 30 anomalous batomorphs have been recorded every 5 years. Sixty‐nine abnormal specimens occurred in the Northern Hemisphere (1.00–60.00 N). The Cortezian (Pacific) and Southeastern Brazil (Atlantic) marine ecoregions stood out with the highest number of these specimens. Mexico recorded 58 anomalous specimens, followed by Brazil (n = 36). Biological, abiotic and anthropogenic factors are probably the leading causes. However, additional studies are necessary to elucidate these speculations. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the suitability of different vertebrae staining techniques for the visualization and counting of growth bands in tropical species of batoids (Narcine leoparda, Urotrygon aspidura, Hypanus longus, Potamotrygon magdalenae) and sharks (Alopias pelagicus, Carcharhinus falciformis, Sphyrna lewini, Sphyrna corona and Mustelus lunulatus). Different cutting thicknesses and staining protocols were tested, analysing the precision and bias of each combination to identify the most accurate technique for estimating age. Vertebral sections of 0.4 mm were more suitable for batoids, except for Narcine leoparda; for this species and for all the shark species assessed, sections of 0.5 mm are recommended. Different combinations of stain and exposure time were required to achieve the best visualizations of vertebral growth band pair for the shark and ray species. Intraspecific variation occurred among vertebrae size of batoids. Our results confirm the importance of defining a suitable species-specific protocol for sectioning and staining hard structures before carrying out an age and growth study to improve the reliability of the age estimates.

Sets of jaws of the sandskates Psammobatis extenta (n = 10), P. lentiginosa (only adult specimens, n = 8) and P. rutrum (only adult specimens, n = 10) were examined by scanning electron microscopy. Female teeth of the three species and those of the immature P. extenta did not show differences, all having monocuspid crushing teeth, with a small, unpronounced or absent cusp. Monognathic heterodonty was observed in adult specimens in both sexes of the three species analyzed. Immature P. extenta and females of the three species differed from the adult males in having a crushing as opposed to a clutching dentition, implying gynandric heterodonty. Teeth of males of P. extenta have pointed, well-pronounced, rounded cusps, whereas males of P. rutrum and P. lentiginosa have elliptical and similar cusps. Immature specimens of P. extenta have small cusps. Teeth of P. lentiginosa have a longitudinal sulcus on their labial face, a character herein hypothesized as a derived condition.

Cartilaginous fishes, as an important group of jawed vertebrates, hold great promise for improving our understanding of vertebrate evolution. Previous studies have established a good staging scheme for shark embryos. However, to date, little attention has been paid to the development of skate embryos. In this study, we established a fine developmental timeline for the Kong skate. We hatched eggs of the Kong skate (Okamejei kenojei) at fixed temperatures (16.5°C ± 0.5°C) while observing three samples every day and recorded the complete embryonic development. The embryo weight and development time were found to have a quadratic relationship. The weight-at-day curve was fitted by y = 0.0005x2 - 0.0109x + 0.0882 (R² = 0.9406). In addition, complete embryonic development from gastrula to skate larvae took 92 ± 5 days. Here, we divided the entire development process into 39 stages. This shows that the jaw of O. kenojei is developed from the first pair of pharyngeal arches, and its body disc is formed by the fusion of the pectoral fin and head. The eyespots began to form from stage 36 and then became thicker and bigger until the young skate broke out of the egg. Notably, we found that males and females develop differently from stage 31; the end of the male pelvic fins expands inward, which develop into copulatory organ-claspers, whereas in the females, they do not expand. To the best of our knowledge, this is the first study to record the embryonic development of eyes, body discs, eyespots, and other organs of O. kenojei in detail. We hope that our work will provide valuable information for researchers to identify specific time points for developing skate embryos.

Systematics and anatomy studies have revealed that characteristics of the batoids skeleton show significant variability and provide relevant information on the phylogenetic relationships of this group. Within this framework, our objective is describing the neurocranium morphology in eight species of batoids. Large variations were found, mainly in the rostrum, number of fontanelles, orientation of nasal capsules, and the condition and development of the pre- and post-orbital processes. These variations allowed us to group these craniums in three morphotypes. The first, including Narcine bancroftii, has unique characteristics, such as a squared rostrum and branched anterorbital cartilages; there are no pre-or postorbital processes, supraorbital crest or rostral appendix. The second morphotype includes Rostroraja texana and Pseudobatus lentiginosus, which have a well-developed rostrum with a rostral appendix in the anterior region, two fontanelles, jugal arches in the occipital region, and pre- and post-orbital processes poorly developed. The third morphotype includes myliobatoids species, which have small or absent rostrum, rostral appendix separated from the cranium, one fontanelle, and developed pre- and post-orbital processes. Most species have morphological variations throughout their development; therefore, when conducting phylogenetic studies, using characters from adult specimens is fundamental. [ABSTRACT FROM AUTHOR]

We report here a diverse assemblage of sharks and batoids representing the genera Carcharhinus, Rhizoprionodon, Galeocerdo, Sphyrna, Myliobatis, Aetobatus, Dasyatis, Pastinachus, Himantura and Pristis from Tapar and Jangadia the two late and early Miocene sites, respectively, of Kutch (Gujarat, India). The shark Rhizoprionodon and batoids, Dasyatis rugosa, D. cf. probsti, Dasyatis sp., Pastinachus and Himantura are being reported for the first time from the Miocene of western coast of India. The presence of Carcharhinus sp., Rhizoprionodon sp., Lamna sp., Negaprion sp., Sphyrna lewini, Myliobatis sp., Aetobatus sp. in the early Miocene Khari Nadi Formation exposed at Jangadia suggest existence of lagoonal, near shore to outer shelf environment. The rich batoid assemblage at the Late Miocene hominoid (Sivapithecus) bearing site of Tapar indicates the presence of a fresh to brackish water environmental condition. The faunal similarity of Miocene chondrichthyan of Indian Ocean and the Mediterranean Sea regions has been assessed using the beta diversity (Sørensen–Dice coefficient) data. The early Miocene elasmobranchs from Kutch shows close affinities with those from Mediterranean Sea. Similarly, in the Indian Ocean region Miocene fauna of Kutch shows close similarity with those of Baripada Beds, Orissa, Bhuban Formation of Mizoram, Gogha Coast, Piram Island and Madagascar. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia 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.)

Despite the long evolutionary history of this group, the challenges brought by the Anthropocene have been inflicting an extensive pressure over sharks and their relatives. Overexploitation has been driving a worldwide decline in elasmobranch populations, and rapid environmental change, triggered by anthropogenic activities, may further test this group's resilience. In this context, we searched the literature for peer-reviewed studies featuring a sustained (>24 h) and controlled exposure of elasmobranch species to warming, acidification, and/or deoxygenation: three of the most pressing symptoms of change in the ocean. In a standardized comparative framework, we conducted an array of mixed-model meta-analyses (based on 368 control-treatment contrasts from 53 studies) to evaluate the effects of these factors and their combination as experimental treatments. We further compared these effects across different attributes (lineages, climates, lifestyles, reproductive modes, and life stages) and assessed the direction of impact over a comprehensive set of biological responses (survival, development, growth, aerobic metabolism, anaerobic metabolism, oxygen transport, feeding, behavior, acid-base status, thermal tolerance, hypoxia tolerance, and cell stress). Based on the present findings, warming appears as the most influential factor, with clear directional effects, namely decreasing development time and increasing aerobic metabolism, feeding, and thermal tolerance. While warming influence was pervasive across attributes, acidification effects appear to be more context-specific, with no perceivable directional trends across biological responses apart from the necessary to achieve acid-base balance. Meanwhile, despite its potential for steep impacts, deoxygenation has been the most neglected factor, with data paucity ultimately precluding sound conclusions. Likewise, the implementation of multi-factor treatments has been mostly restricted to the combination of warming and acidification, with effects approximately matching those of warming. Despite considerable progress over recent years, research regarding the impact of these drivers on elasmobranchs lags behind other taxa, with more research required to disentangle many of the observed effects. Given the current levels of extinction risk and the quick pace of global change, it is further crucial that we integrate the knowledge accumulated through different scientific approaches into a holistic perspective to better understand how this group may fare in a changing ocean.

Here, we use vertebral microchemistry to investigate the habitat use patterns of the longnose stingray Hypanus guttatus in the northern and northeastern regions of Brazil, and to evaluate the existence of potential nurseries of the species. Samples were collected in Maranhão, Rio Grande do Norte and Pernambuco states between 2008 and 2019. Trace element concentrations of Ba:Ca, Mg:Ca, Mn:Ca and Sr:Ca in vertebrae were determined through laser ablation inductively coupled plasma mass spectrometry. We used one‐step permutational ANOVAs to evaluate multi and single‐element differences in element:Ca ratios among life stages and sexes across and within sites. Element signatures differed among all sites for both single and multi‐element settings. However, there were few differences among life stages within sites, except for Mn:Ca between life stages for Maranhão state, and between sexes for Sr:Ca for both Pernambuco and Rio Grande do Norte, and Ba:Ca for Rio Grande do Norte. Furthermore, all multi and single‐element analyses across locations were significant and highlight the strong differences by sites. We also performed a nonmetric multidimensional scaling analysis, which demonstrated the strong differences for samples from Rio Grande do Norte and the other two sites. By analysing the lifetime transects of each sample, we observed that there was little variation in all element:Ca ratios within sites. Therefore, we argue that the longnose stingray likely does not display extensive habitat use shifts and fulfils much of its life cycle within each area. Finally, we obtained no evidence of nurseries for any site and suggest this is likely a pattern across the species distribution. Future studies investigating habitat use with samples from larger specimens (disc width > 90 cm, >15 years) are needed to better understand the species habitat use patterns across all size ranges. [ABSTRACT FROM AUTHOR]

Species diversity assessments are an important step to evaluate the conservation status of a community, both in marine and terrestrial ecosystems. These assessments are pivotal if related to both, the constant increase of human pressure on ecosystems and the anthropogenic climate change occurring nowadays. Sharks and rays are globally threatened, and the situation is particularly alarming in the Mediterranean Sea where more than 50% of species are listed at risk of extinction by the International Union for Conservation of Nature (IUCN). In this paper, we revise and discuss the chondrichthyan species richness of the Mediterranean and the Black Sea. Through an accurate review of published taxonomic studies, historical data on species occurrence, analyses of scientific survey data and biodiversity databases and other scientific papers, we produced a revised list of species whose presence in the Mediterranean Sea is confirmed or highly probable and discussed on current taxonomic and occurrence disputes on the species that are instead rarer or claimed to be locally extinct. We listed a total of 88 species, representing 30 families and 48 genera that are currently present in the Mediterranean and the Black Sea. This number includes 48 shark species, 38 batoids, and 2 chimaeras. The review represents a reference for future conservation assessments of cartilaginous fish in the region and a guide for decision-makers when promoting the sustainable exploitation of fisheries resource within an ecosystem-based framework. This paper can help to set a baseline of the Mediterranean species and thus resolve some uncertainties regarding their conservation status, explaining the reasons for their prolonged absence in the reports. Indeed, failure to record over time may not be due to grubbing up, but because after careful review this species was not really part of the Mediterranean fauna.

The occurrence of Bennett’s stingray, Hemitrygon bennettii (Müller et Henle, 1841), is confirmed from Indian waters, based on a single male specimen (370 mm DW) collected from Visakhapatnam, western Bay of Bengal on 28 January 2017. Existing, updated reports on the distribution of the species, places it in the Indo-Pacific region with the western limit being the Strait of Malacca. With the presently confirmed occurrence from the western Bay of Bengal, the known distribution of the species extends further westwards to the Indian east coast, although it is likely to be a rare species in Indian waters.

In the study, the authors evaluate the spatial distribution pattern of vermiculate electric‐ray Narcine vermiculatus using geostatistical techniques to predict its spatial distribution and indicate its reproduction strategy. From January 2008 to December 2009, 3333 specimens of vermiculate electric‐ray were caught. Total length (LT), sex, maturity stage, catch location and depth were recorded for each specimen. The LT of vermiculate electric‐ray ranged from 6.7–24.6 cm. The authors estimate an irregular spatial structure, with a high‐density patch (x¯= 53 ind. ha−1) located on the east coast, which concentrates 65.2% of the specimens. The high‐density patch consists mainly of large juveniles (13.3–19.5 cm LT), sub‐adults (14.0–19.8 cm LT) and young adults (14.7–21.3 cm LT). Data indicate that adults migrate to the high‐density patch to reproduce. Males reached maturity at 14.5 cm LT, whereas females reached maturity at 19.3 cm LT. Vitellogenesis in female vermiculate electric‐ray begins in June; ovulation, mating, fertilization and gestation in October and birth begins in February. This indicates an annual cycle with vitellogenesis and consecutive gestation, in females synchronized in reproduction. Fecundity was 1–8 (x¯= 4), and the sex ratio of embryos was 1:1. The birth occurred between February and April, with an average size at parturition of 6.3 cm LT. Incidental capture of sub‐adults and adults of N. vermiculatus by bottom trawls threatens the survival of this species. [ABSTRACT FROM AUTHOR]

This updated checklist of chondrichthyans from the Gulf of California (GC) with notes on zoogeography, conservation status, and commercial value includes 2 subclasses, 14 orders, 31 families, 55 genera, and 106 species. Euselachii (Batomorphi 44.3% and Selachii 51.8%) is the most diverse subclass (13 orders, 29 families, 53 genera, and 102 species). The order Carcharhiniformes (4 families, 16 genera, and 36 species) and Myliobatiformes (6 families, 11 genera, and 24 species) represent 56.6% of the total cartilaginous fish diversity in the GC. Based on the analysis of biogeographic affinities, most species include their ranges of distribution into the “Sinus-Californian” (55.7%), Mexican (41.5%), and Panamic (36.8%) provinces; 29 species are circumtropical, 7 amphipacific, 5 amphiamerican, and 4 endemic. Based on the IUCN Red List, 1 species is “Critically Endangered,” 2 are “Endangered,” 14 are “Vulnerable,” 23 are “Near Threatened,” 26 are of “Least Concern,” 3 “Not Evaluated,” and 36 are “Data Deficient.” Mexican laws fully protect 9 species classified as “Threatened,” at “Risk of Extinction,” or under “Special Protection,” whereas the rest are protected from fishing at least during 3 months of the year. Thirty-seven species (35%) are of commercial value; another 30 (28%) rare species of low commercial importance have been reported in the catches of artisanal and semi-industrial fisheries during the last 2 decades. Sørensen's coefficient of similarity and cluster analysis between major faunal divisions in the GC suggest the existence of 2 large chondrichthyan assemblages for this region ([NGC-CGC] + [SGC]). This study increases to 106 the species richness of Chondrichthyes known in the GC and serves as the baseline for formulating and implementing of conservation programs for this group of cartilaginous fish. [ABSTRACT FROM AUTHOR]