Order Lamniformes consists of 15 extant shark species that are ecologically diverse and utilize different swimming modes and speeds. Family Lamnidae includes the shortfin mako, porbeagle, and white shark which are fast, athletic sharks that swim using oscillations confined to the caudal body and fin. Other lamniforms, like the common thresher shark (Alopiidae), sand tiger (Carchariidae), and basking shark (Cetorhinidae), swim via oscillations that begin anteriorly, impacting a greater proportion of the axial body. Swimming oscillations subject the body to repeated bending cycles, including the cartilaginous vertebral column, the main longitudinal axis of the body. Vertebrae are mineralized with the amount and arrangement varying among species. We investigated morphological variation in lamniform shark vertebrae to understand adaptations to locomotive demands among species. We examined vertebral morphology and mineral architecture of lamniform centra across three body regions (anterior, middle, and posterior) and among six species (shortfin mako, porbeagle, sand tiger, white, common thresher, and basking shark) through micro-computed tomography scans. We analyzed morphology and structure of 139 vertebrae from 24 sharks using meristics, principal component analyses, and 3D landmark-based geometric morphometrics. Through 3D quantification, we identified regional patterns in centrum size and mineral amount which also varied across shark families. In the lamnids, centra morphometrics are largest in the mid-body and decrease posteriorly simultaneous with increased counts of lamellae. Together, these trends suggest the middle body region is stabilized while allowing for rapid lateral oscillations at the precaudal pit. Cranio-caudally compressed centra with high quantities of lamellae were characteristic for common thresher shark centra, likely to support loading in multiple planes from extreme axial bending during tail-whipping behaviors. In the sand tiger and basking shark, we quantified opposing trends-large anterior centra decreased in size along the column with reduced mineralization for slow swimming. We calculated scaling relationships of mineral volume with shark size and identified a negative allometric relationship, suggesting adult sharks may adapt internal architecture rather than contributing to overall centrum size. This comprehensive analysis of calcified structure in lamniform shark centra provides a greater understanding of skeletal tissues and the adaptation of mineralized cartilage to support swimming and ecological needs.
Global shark mortality continues to rise despite increasing regulations aimed at limiting shark fishing and trade. Regulatory measures may influence shark product markets, but this relationship has been difficult to quantify because of fragmented and poorly resolved data. We present a global analysis evaluating the effects of domestic shark finning regulations on trade in shark products across 188 countries. Using causal inference methods and the Aquatic Resource Trade in Species database (2007-2020), we find weak and statistically insignificant effects of finning regulations on overall shark trade volumes. However, long-term trends suggest that countries adopting finning regulations tend to reduce exports, modestly increase imports, and maintain relatively stable domestic consumption. Our framework provides a broader approach for investigating the economic pathways and drivers of mortality associated with sharks and other traded wildlife species.
Sharks respond to low frequency pulsed sounds but are presumed to lack the capacity to detect these sounds beyond the acoustic near field, where particle motion dominates. This study quantified the distance that blacktip sharks (Carcharhinus limbatus) oriented to sound stimuli and determined that responses could be consistently initiated from the acoustic far field. Using an aerial drone, C. limbatus were filmed responding to sound stimuli (100-200 Hz; 200-400 Hz; and 400-800 Hz) generated by an underwater speaker. Upon detection, C. limbatus elicited a sudden 20-160° turn away from the speaker and rapidly swam away. Sharks responded to all frequencies from at least 62 m, and 71.6% of all responses (n = 209) occurred in the far field. Sharks never responded to a high frequency (10 kHz) control stimulus of comparable volume. The sound pressure levels for all stimuli were measured in situ and used to model the propagation away from the source. This permitted direct calculation of the stimulus intensity for the point at which each shark initiated a response. A greater sound pressure level was required to elicit a response at higher frequencies, supporting earlier work that demonstrated greatest sensitivity to low frequencies. The ability of blacktip sharks to detect and orient away from a sound stimulus at distances that extend beyond the acoustic near field, suggests that they are detecting particle motion in the far field.
Shark species are among the most vulnerable marine fishes facing impacts from fisheries. To ensure the international fin trade does not threaten their populations, several species have been listed in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix II. However, the lack of data on fin-to-body weight ratios makes it difficult to accurately estimate the biomass of harvested sharks based on their traded fins and weakens CITES enforcement. This study determines species-specific fin-to-body weight ratios for shark species caught by the artisanal fishery in the southern Gulf of Mexico. Wet fin weights of primary fins from 479 individuals, belonging to 19 species and six families, indicated that Carcharhinus leucas (43.6%), C. plumbeus (18.8%), C. obscurus (15.0%) and Sphyrna lewini (6.6%) were the most significant large-bodied species involved in the international shark fin trade from the southern Gulf of Mexico. The species-specific mean wet fin weight to total body weight ratios ranged from 1.22% to 3.44%, while wet fin weight to trunk weight ratios varied between 1.40% and 5.73%. Furthermore, the dry fin weight-to-trunk weight ratios oscillated from 0.52% to 1.71%, and the dry fin weight-to-trunk weight ratios ranged from 0.58% to 2.86%. The mean dry-to-wet fin conversion factor was estimated at 42.9%. Alopias superciliosus, C. altimus, C. leucas, C. obscurus, C. plumbeus and Isurus paucus exhibited the highest fin-to-body weight ratios. Our findings provided a practical tool for assessing shark population exploitation based on shark fin trade volumes, contributing to CITES enforcement and management strategies.
Notable characteristics of bonnethead sharks (Sphyrna tiburo) include an omnivorous diet and sexual dimorphism in cephalofoil morphology, with males exhibiting a more prominent tip at the anterior of their snout, which one study hypothesized develops with sexual maturity. However, it is not known if this characteristic is prevalent in all bonnethead subpopulations, nor whether it is consistent across their range. The potential ecological or physiological function (mating, feeding, swimming energetics) of this difference is also unknown. In this study, cephalofoil morphology was assessed by sex and maturity for bonnethead sharks in Biscayne Bay and Tampa Bay, Florida. Additionally, muscle biopsies were analyzed for stable isotope composition to explore potential associations with diet. Sharks were caught between May 2022 and May 2023 via longline (Biscayne) and gillnet (Tampa). Body measurements and dorsal and ventral photographs of the head were taken as part of a scientific workup and sharks were promptly released. Images were analyzed in ImageJ to determine a best-fit parabolic curve; comparisons of cephalofoil curvature were based on the absolute "a" coefficient from the parabolic curve equation y = ax2 + bx + c via ANOVA and PERMANOVA. Shape coordinates were also analyzed with a Procrustes ANCOVA to test for differences among groups while controlling for covariates. In both Biscayne Bay and Tampa Bay, males and females had significantly different head shapes, but, contrary to previous hypotheses, the cephalofoils of both sexes became rounder at maturity. There was greater rounding in female cephalofoils than male, and females experienced greater changes in cephalofoil shape as they matured. Diet, as examined through δ13C and δ15N values of muscle biopsies, showed isotopically distinct food webs with differing ontogenetic dietary patterns between Biscayne Bay and Tampa Bay following ANOVA and ANCOVA tests, but was not correlated to bonnetheads' cephalic sexual dimorphism. From this result, we hypothesize that younger and smaller bonnethead sharks of both sexes may benefit from the pointed cephalofoil for enhanced swimming performance, and that larger adult females may outgrow these benefits through development of physical characteristics, including larger body sizes necessary for reproduction. Características notables de los tiburones cabeza de pala (Sphyrna tiburo) incluyen una dieta omnívora y dimorfismo sexual en la morfología del cefalofolio; machos presentan una punta más prominente al frente del hocico, que un estudio hipotetizó se desarrolla con la madurez sexual. Sin embargo, desconoce si esta característica está prevalente en todas las subpoblaciones ni si es consistente a través de su gama. Tampoco se conoce la posible función ecológica o fisiológica (apareamiento, alimentación, energía de la natación) de esta diferencia. En este estudio, la morfología cefálica fue evaluada por sexo y madurez en tiburones cabeza de pala en la bahía Biscayne y la bahía Tampa en Florida. Además, se analizaron biopsias musculares para determinar la composición de isótopos estables con el fin de explorar posibles asociaciones con la dieta. Tiburones fueron atrapados desde mayo de 2022 hasta mayo de 2023 con palangres (Biscayne) y redes agalleras (Tampa). Se tomaron medidas del cuerpo y fotos de los lados dorsales y ventrales de la cabeza antes de que los tiburones fueran devueltos. Las imágenes fueron analizadas en ImageJ para determinar una curva parabólica de mejor ajuste; las comparaciones de la curva cefálica se basaron en el coeficiente absoluto “a” de la ecuación parabólica y = ax2 + bx + c con ANOVA y PERMANOVA. Coordenadas de forma fueron analizadas con Procrustes ANCOVA para comprobar diferencias entre grupos mientras controlaba las covariables. En ambos la bahía Biscayne y la bahía Tampa, machos y hembras tenían formas de cabeza significativamente diferentes, pero al contrario al hipótesis anterior, los cefalofolios se volvieron más redondeos con la madurez. Los cefalofolios de hembras se pusieron más redondos que los de los machos y también la forma de los cefalofolios de hembras cambió más cuando maduraron. La dieta, examinada a través de los valores de δ13C and δ15N de las biopsias musculares, mostró redes tróficas isotópicamente distintas con diferentes patrones alimenticios ontogenéticos entre las dos bahías tras exámenes de ANOVA y ANCOVA, pero no fue correlacionada con el dimorfismo sexual cefálico. A partir de ese resultado, nosotros hipotetizamos que tiburones cabeza de pala menores y más pequeños podrían beneficiarse de un cefalofolio más puntiagudo para mejorar el rendimiento natatorio y que hembras adultas más grandes pueden superar estos beneficios a través del desarrollo de características físicas, incluyendo tamaños corporales mayores, que pueden ser necesarios para la reproducción.
The presence of anthropogenic microparticles (particles <5 mm in any dimension) is being increasingly reported, yet little is known about their abundance, distribution, and bioavailability in marine environments. Microplastics (plastic polymers <5 mm) are persistent anthropogenic microparticles that contaminate marine environments and often enter food webs through ingestion. Sharks are sentinel species in the ocean, yet studies characterizing microparticle, or more specifically microplastic, ingestion in sharks are scarce. The objectives of this study were to describe and quantify microparticles in the feces of white sharks (Carcharodon carcharias). Samples were obtained from a total of 35 white sharks, including seven young-of-the-year, 17 juveniles, six subadults, and five adults inhabiting the Western North Atlantic Ocean. Microparticles were isolated, analyzed with a stereomicroscope to determine size, shape, and color, and characterized by polymer type using Fourier transform infrared (FTIR) spectroscopy. Anthropogenic microparticles were detected in all fecal samples. The mean ± standard deviation of microparticles per sample was 7.5 ± 4.2, and of those, 1.4 ± 1.3 were microplastics. No significant differences in the abundance of microplastics were detected by age class, sex, or collection location, year, or seasonal residency; however, differences in microparticle composition were observed across collection locations. Rayon and cellulose were the most abundant microparticle polymers, and polyester, polypropylene, and nylon were the most abundant microplastic polymers. White, black, and blue were the most common colors of microparticles and microplastics. This research contributes much-needed data from a top-level predator in marine ecosystems. Assessing microplastic content in white shark feces can serve as a non-lethal indicator of environmental contamination.
Plastic pollution is increasingly documented across marine environments, yet exposure data remain absent for most shark species. We examined the gastrointestinal contents of 44 juvenile sharks representing three species: gummy shark (Mustelus antarcticus), southern saw shark (Pristiophorus nudipinnis), and elephant (or ghost) shark (Callorhinchus milii) collected as bycatch from demersal trawl and longline fishing in the Bass Strait off north-eastern Tasmania in September 2018. Gastrointestinal tracts were excised intact and contents rinsed through stacked sieves and examined for micro- and macro-plastics (>1 mm). No plastics were detected in any of the 44 individuals examined. While these null results may reflect genuinely low exposure in this region, we emphasise that reporting such findings is essential for establishing baseline conditions against which future change can be measured. Given the commercial and ecological importance of these species in southern Australian waters, repeat sampling over time is strongly encouraged to detect any emerging trends in plastics exposure.
Sleeper sharks (family Somniosidae) are large, slow-growing deep-sea sharks that are rarely documented in the southeastern Pacific, and records from the Chilean waters have remained taxonomically uncertain. Here, we report a confirmed record of a large-bodied southern Somniosus from northern Chile based on a gravid female incidentally captured by a commercial deep-sea longline fishery off Antofagasta and a late-stage male embryo aborted during handling. The embryo measured 90.5 cm in total length and exhibited morphological and meristic characters consistent with large-bodied S. antarcticus, including a cylindrical body, short rounded snout, spineless dorsal fins, hook-like dermal denticles, and a 40-turn spiral valve. Additionally, a 639 bp fragment of the mitochondrial cytochrome C oxidase subunit I (COI) gene was obtained from both the female and embryo, and the two sequences were identical, consistent with maternal inheritance. Comparative analyses using public records placed the Chilean haplotype within the large-bodied Somniosus species complex. The Chilean haplotype was identical to an Antarctic record labelled S. pacificus and differed by two substitutions from a New Zealand record labelled S. antarcticus. However, the COI does not fully resolve species boundaries within the pacificus/antarcticus complex, as the divergence between nominal species remains low. These results provide the first well-documented record of the Antarctic sleeper shark in northern Chile and expand the documented occurrence of southern large-bodied Somniosus along the Chilean margin. More broadly, this record highlights the importance of integrating internal meristics, morphology, and molecular data when documenting rare deep-sea sharks in fishery bycatch.
The tiger shark (Galeocerdo cuvier) is a dominant marine elasmobranch predator whose respiratory physiology and gill structure enable the oxygen uptake necessary for its significant ecological role in sustaining balance within oceanic environments. The present study investigated the histological, histochemical, and ultrastructural characteristics of gill tissue in the tiger shark to elucidate the morphological adaptations that enable efficient respiration in marine environments. Histologically, the gills were housed in antero-posteriorly compressed gill pouches, with the first pair being hemibranchs and the remaining pairs being holobranchs. The respiratory surfaces consisted of cartilage-supported gill arches bearing numerous filaments with secondary lamellae lined by thin epithelium comprising pavement cells, chloride cells, and sparse goblet cells. Semithin section analysis identified undifferentiated basal cells, lymphocytes, pillar cells, and nucleated erythrocytes within the lamellar structure. Notably, rodlet cells at various maturation stages and intraepithelial telocytes with characteristic telopods were observed throughout the gill epithelium and septum. The well-developed interbranchial septum, a distinguishing feature of elasmobranch gills, exhibited stratified epithelium with diverse cell types and extensive telocyte networks. Histochemical staining demonstrated the presence of polysaccharides and neutral mucins (PAS-positive) in the basement membranes and goblet cells, weak alcian blue staining for acid mucin, abundant collagen fibers in supporting structures, as shown by Masson's trichrome, and elastic fibers in the pharyngeal cavity, gill arches, and blood vessel walls as investigated by orcein stain. SEM revealed well-developed primary lamellae bearing comb-like secondary lamellae, a granular epithelial surface featuring mucous goblet cells and chloride cell projections. The integument overlying the gill region showed densely packed placoid scales (dermal denticles). In conclusion, these findings highlight the complex cellular organization and structural specializations of tiger shark gills that facilitate efficient gas exchange and osmoregulation. Our study sheds light on the adaptive strategies that enable tiger sharks to thrive in their marine environment, providing important new insights into the relationship between gill anatomy and ecological function.
Aiming at the inherent limitations of the basic White Shark Optimizer (WSO), such as insufficient population diversity, unbalanced global and local search mechanisms, and weak convergence in the later stage, this paper proposes an Improved White Shark Optimizer (IWSO). The algorithm is improved from the following three aspects: Firstly, the Tent chaotic map is introduced to replace the traditional random initialization in the population initialization stage. Secondly, an adaptive nonlinear convergence factor and a dynamic inertia weight adjustment strategy are designed to focus on the fine search in the neighborhood of the optimal solution. Thirdly, the Levy flight perturbation mechanism and the elite opposition-based learning strategy are integrated to expand the search range and further accelerate the convergence speed. To verify the effectiveness and superiority of the IWSO algorithm, the CEC2017 test suite is selected for simulation experiments, and the IWSO is systematically compared with seven other representative swarm intelligence algorithms. The experimental results show that the IWSO is significantly superior to all comparison algorithms in multiple evaluation indicators, including minimum makespan, average convergence value, standard deviation, and successful convergence rate, on scheduling instances of different scales and difficulties. The convergence curve remains leading throughout the iteration process and shows a smoother convergence trend. The multi-strategy enhanced white shark optimizer proposed in this paper effectively overcomes the inherent defects of the basic algorithm, significantly improves the solution accuracy and convergence efficiency of the job shop scheduling problem, and has high theoretical research value and practical engineering application prospects. In the future, the multi-strategy improved White Shark Optimizer will be extended to multi-objective job shop scheduling, dynamic disturbance job shop scheduling, and large-scale production scheduling scenarios with numerous workpieces and machines.
"Shark-fin" is a rare but serious electrocardiogram (ECG) pattern often suggestive of proximal left anterior descending or left main coronary artery (LMCA) involvement. A 66-year-old man came to our hospital for acute chest pain and cardiogenic shock. ECG showed a shark-fin waveform in aVR lead along with diffuse ST-segment depression. Urgent coronary angiography demonstrated complete thrombotic LMCA occlusion and primary percutaneous coronary intervention with stent implantation allowed for hemodynamic stabilization and ECG normalization. Shark-fin is one of a series of patterns described as "ST-segment elevation myocardial infarction equivalent." It usually affects the anterior leads, expressing a left anterior descending artery critical lesion or occlusion. Here, the presence of this sign in the aVR lead was associated with LMCA acute, total, occlusion and a rapid diagnosis was crucial to enable the most appropriate treatment. Shark-fin sign is an "ST-segment elevation myocardial infarction equivalent" pattern. When involving the aVR lead, it should raise immediate suspicion for LMCA occlusion. Rapid recognition and emergent reperfusion can be lifesaving.
This study presents the first morphometric examination of the pectoral fins of 19 shark species in the Libyan Mediterranean Sea using 88 specimens collected from November 2023 to November 2024. The observed morphometrics successfully differentiate between benthic Squatiniformes, demersal Squalidae, triakis, and pelagic lamnids and carcharhinids. Statistical analysis revealed significant interspecific variation (p < 0.05) in different calculated ratios, with the highest level of discrimination power being shown by PL/PF and PA/PB. Multivariate data analyses also supported unique morphological groupings of ecologically and phylogenetically close members. The present study also recorded significant biogeographical information with five shark species being first reported in Libyan waters: Heptranchias perlo (Bonnaterre, 1788), Squalus megalops (Macleay, 1881), Carcharhinus altimus (Springer, 1950), Carcharhinus obscurus (Lesueur, 1818), and Squalus mitsukurii (Jordan and Snyder, 1903). It is noteworthy that S. mitsukurii was first reported in the entire Mediterranean Sea, a considerable expansion of its known range. These results are important to emphasize the ecological significance of the area and make further observations to improve our knowledge of shark diversity and distribution in the southern Mediterranean. In addition, the present findings help to underline the high diagnostic significance of pectoral-fin morphometrics and the usefulness of the present methods for species identification and shark biodiversity in the southern Mediterranean Sea.
Whale sharks (Rhincodon typus) are migratory species known to form temporary coastal aggregations in regions of high plankton density, such as Bahía de los Ángeles (BLA), Mexico. Due to various anthropogenic threats, the species is classified as vulnerable, underscoring the need for effective and non-invasive monitoring strategies. This study explores the integration of drone-based remote sensing with deep learning (DL) techniques for the automated recognition and tracking of whale sharks. In October 2023, 59 drone flights-42 from boats and 17 from land-were conducted, resulting in 23 recorded sightings. Two DL-based approaches were implemented: DeepLabCut (DLC), based on pose estimation, and multi-scale patch (MSP), based on image region classification. Both strategies employed convolutional neural networks, with data augmentation and transfer learning techniques to enhance performance. The most effective model, MSP with multi-size and overlapping patches, achieved a macro F1 score of 0.91 and a covered area metric of 0.65. Statistical analysis indicated that environmental and operational factors-including turbidity, solar glare and external agents-had minimal impact on predictive performance. These results highlight the potential of DL-enhanced drone monitoring for scalable, accurate and non-invasive recognition and tracking of whale sharks, supporting ecological research and conservation efforts in BLA and comparable marine environments.
Offshore wind energy plays a crucial role in the transition to low-carbon power generation. The expansion of offshore wind farms (OWFs) introduces anthropogenic electromagnetic fields (EMFs) from subsea power cables. Elasmobranchs, including sharks and rays, are sensitive to natural electric and magnetic fields used for navigation and prey detection, making them potentially vulnerable to anthropogenic EMFs as they may alter orientation, foraging or habitat use. Coastal shelf seas, where most OWFs are constructed, often overlap with essential elasmobranch habitats, including complex biogenic structures such as mussel beds that provide foraging and refuge opportunities. We aimed to determine whether exposure to an AC-EMF representative of subsea power cables and/or complex mussel substrate over non-complex substrate influences behaviour and substrate preferences in juvenile small-spotted catsharks (Scyliorhinus canicula). This study investigated the behavioural responses of 14 juvenile S. canicula exposed to a gradient of alternating current (AC) EMF (max. RMS 2 μT) and complex biogenic mussel substrate in a 22 factorial design in a circular preference chamber. Across 28 trials, time spent and distance travelled in each quadrant did not differ with EMF exposure and/or the presence of complex biogenic substrate. Hidden Markov models revealed subtle but significant changes in behavioural states (inactive, local activity, transit), where sharks were more inactive (+6%pt.) and less locally active (-5%pt.) in the EMF + mussel quadrant compared to the bare and EMF-only quadrants, and increased transiting behaviour (+6%pt.) in the mussel-only quadrant relative to the EMF + mussel quadrant. These findings show that S. canicula juveniles show no preference in substrate or alternating-current EMF exposure, but they did subtly change their behaviour. Future work should examine direct-current systems and field-based tracking and assess the extent to which these observations generalise to field settings and other elasmobranchs.
In May of 2022, an aquarium-maintained broadnose sevengill shark (Notorynchus cepedianus) developed proliferative skin lesions that prompted pathologic and molecular investigation. Histopathologic examination revealed epidermal hyperplasia consisting of proliferation of spinous epithelial cells with mild dysplasia. Metagenomic sequencing identified a novel adomavirus with an 18,834 base pair circular double-stranded DNA genome. The virus, provisionally named broadnose sevengill shark adomavirus (7AdoV), contains two bidirectionally expressed protein-coding gene sets. Genomic annotation and structural predictions of proteins were used to contextualize 7AdoV phylogenetically and functionally. Transcriptomic analysis showed that expression of the structural late gene set was higher than the replicative early gene set at the time of diagnostic sampling. In situ hybridization using RNAscope technology localized transcripts of the adomavirus Wasp gene to epithelial cells of the hyperplastic epidermis. Infection by this novel adomavirus was associated with superficial and proliferative lesions that were self-limiting and resolved in this shark.
The Greenland shark (Somniosus microcephalus) is a deep-sea vertebrate inhabiting the cold waters of the North Atlantic and Arctic Ocean and is renowned for its exceptional longevity, with individuals estimated to live for more than 400 years. It has also been proposed as a candidate species exhibiting negligible senescence. This narrative review synthesizes current knowledge on the biological mechanisms that may contribute to this phenotype. Potential contributing factors include its extreme environment, low metabolic rate and remarkably late sexual maturation, all of which may reduce cumulative physiological stress over time. At the molecular level, recent genomic studies have identified distinctive features, including duplications of DNA repair genes and structural variation in the tumour suppressor protein p53, which are consistent with enhanced genome maintenance, although their functional significance remains to be experimentally validated. Additional mechanisms, such as proteostatic resilience, antioxidant defences and immune adaptations, may further support long-term cellular homeostasis. Collectively, these observations suggest that the Greenland shark possesses biological characteristics that could influence multiple hallmarks of ageing, including genomic stability, proteostasis and intercellular communication. Emerging evidence also indicates resistance to age-related functional decline in systems such as vision and cardiac function. Taken together, these characteristics highlight the Greenland shark as a valuable, yet still underexplored, model for investigating the biology of longevity and resistance to ageing. Further research in this species may provide insights into the mechanisms underlying healthy ageing across vertebrates and generate hypotheses for future translational studies.
Illegal wildlife trade and other forms of wildlife crime pose significant threats to global biodiversity. Accurate species identification of wildlife products is crucial for effectively combating illegal wildlife trade. In recent years, forensic species identification using molecular methods has gained increasing attention. Here, we report a case involving 1777 trafficked fish maws and 18,170 trafficked shark fins. We employed DNA barcoding for forensic species identification and a large-sample inference strategy for population estimation. A total of 325 samples (197 fish maws and 128 shark fins) were randomly selected for DNA testing based on their pre-classified morphological categories. Two DNA barcodes (COI and 16S) were used, and sequence alignment was conducted using the NCBI GenBank and BOLD systems. Phylogenetic analyses were performed based on sequences detected from the samples and reference sequences, with results consistent with the sequence alignment. Consequently, seven species were identified, four of which, corresponding to approximately 17,351 to 18,170 specimens, are listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
Total mercury (THg) was quantified in dorsal muscle from 12 blue sharks (Prionace glauca; six males and six females; 167-230 cm total length) landed at the artisanal fishing port of Ilo, southern Peru, in October 2021. THg was determined by cold-vapour atomic absorption spectrometry at an ISO/IEC 17025-accredited laboratory. Concentrations ranged from 0.021 to 0.330 mg kg-1 wet weight, with a mean of 0.156 ± 0.102 mg kg-1. All samples were below the applicable regulatory limits for shark and represented 1.3-20.6% of the Codex Alimentarius maximum level for methylmercury (1.6 mg kg-1), for which THg may be used as a screening measure. THg increased significantly with total length (Pearson r = 0.768, p = 0.003). Females had higher mean concentrations than males, although the difference was not statistically significant and should be considered preliminary. Dietary exposure was evaluated using fresh-products (40 g day-1) and total-products (70 g day-1) screening scenarios derived from Peruvian apparent-consumption statistics. Under the fresh-products scenario, Target Hazard Quotient (THQ) values were 0.98 for general adults and 2.09 for children aged approximately 9-10 years; under the total-products scenario, they increased to 1.71 and 3.65, respectively. Estimated weekly intake remained below the methylmercury Provisional Tolerable Weekly Intake (PTWI) for adults but reached 159.7% for children under the total-products scenario. These findings provide an independent preliminary local reference dataset for P. glauca landed at Ilo. Although measured THg concentrations were low, the conservative exposure scenarios indicated potential concern for children, highlighting the need for larger monitoring datasets, methylmercury speciation, and local shark-consumption surveys.
The International Union for Conservation of Nature (IUCN) Red List of Threatened Species is a critical measure of global aquatic and terrestrial biodiversity status. It is also the basis for the Red List Index, which tracks extinction risk over time. Sharks, rays, and chimaeras (Chondrichthyes) have now been comprehensively assessed twice (1996-2011 and 2012-2021) with hindcast assessments from 1970 onward, yielding an unprecedented extinction risk trajectory for an aquatic vertebrate class. The three-decade success of the IUCN Species Survival Commission (SSC) Shark Specialist Group (SSG) in providing updated and evidence-based assessments stems from sustained and coordinated activities by SSG members. We examined how a community of dedicated experts organized to fill gaps in key information to inform Red List assessments. From this evaluation, we identified six key lessons related to membership, taxonomic changes, implementation of the precautionary approach, information prioritization, assessment standardization, and policy efforts. However, existing challenges, including resource constraints and assessment discrepancies at different spatial scales, need to be addressed to ensure Red List assessments stay on pace with advances in conservation. With the second global assessment of chondrichthyans completed, it is appropriate to reflect on the evolution of the SSG and its achievements over three decades to highlight new tools and approaches to red listing and to identify priorities for the immediate future that are also applicable to other aquatic taxa with limited data, slow life histories, and exposure to high levels of fishing. Conclusiones extraídas de tres décadas de evaluaciones de la Lista Roja de la UICN que impulsan la conservación de tiburones, rayas y quimeras Resumen La Lista Roja de Especies Amenazadas de la Unión Internacional para la Conservación de la Naturaleza (UICN) es un indicador fundamental del estado de la biodiversidad acuática y terrestre a nivel mundial. También constituye la base del Índice de la Lista Roja, que da seguimiento al riesgo de extinción a lo largo del tiempo. Los tiburones, las rayas y las quimeras (Chondrichthyes) han sido evaluados exhaustivamente en dos ocasiones (1996–2011 y 2012–2021), con evaluaciones retrospectivas a partir de 1970, lo que ha permitido obtener una trayectoria del riesgo de extinción sin precedentes para una clase de vertebrados acuáticos. El éxito de tres décadas del Grupo de Especialistas en Tiburones (SSG) de la Comisión de Supervivencia de Especies (SSC) de la UICN en proporcionar evaluaciones actualizadas y basadas en evidencia se debe a las actividades sostenidas y coordinadas de los miembros del SSG. Examinamos cómo una comunidad de expertos comprometidos se organizó para llenar las brechas en la información clave necesaria para fundamentar las evaluaciones de la Lista Roja. A partir de esta evaluación, identificamos seis lecciones clave relacionadas con la membresía, los cambios taxonómicos, la implementación del enfoque de precaución, la priorización de la información, la estandarización de las evaluaciones y los esfuerzos en materia de políticas. Sin embargo, es necesario abordar los desafíos existentes, entre ellos las limitaciones de recursos y las discrepancias en las evaluaciones a diferentes escalas espaciales, para garantizar que las evaluaciones de la Lista Roja se mantengan al día con los avances en conservación. Ahora que se ha completado la segunda evaluación global de los condrictios, es oportuno reflexionar sobre la evolución del SSG y sus logros a lo largo de tres décadas para destacar nuevas herramientas y enfoques para la inclusión en la Lista Roja e identificar prioridades para el futuro inmediato que también sean aplicables a otros taxones acuáticos con datos limitados, ciclos de vida lentos y expuestos a altos niveles de pesca. 国际自然保护联盟(IUCN)《濒危物种红色名录》是衡量全球水生和陆地生物多样性状况的重要标准, 也是“红色名录指数(Red List Index)”的基础, 该指数用于追踪物种随时间推移的灭绝风险。鲨鱼、鳐鱼和银鲛(软骨鱼纲)迄今已接受过两次全面评估(1996–2011年和2012–2021年), 并结合了自1970年以来的回顾性评估, 得到了水生脊椎动物纲首个灭绝风险轨迹。IUCN物种生存委员会鲨鱼专家组在过去三十年里成功提供了最新且基于证据的评估, 这得益于鲨鱼专家组成员持续且协调一致的行动。本研究分析了一群敬业的专家如何组织起来, 填补关键信息空缺, 从而为《红色名录》评估提供依据。通过此次评估, 我们总结出六项关键经验教训, 涉及专家组成员、分类学变化、预防方法实施、信息优先级排序、评估标准化, 以及政策工作。然而, 为确保《红色名录》评估能够跟上保护工作的进展, 我们仍需应对现有挑战, 包括资源限制及不同空间尺度上的评估差异。随着第二次软骨鱼类全球评估的完成, 现在正是回顾鲨鱼专家组三十年来发展历程及其成就的合适时机, 以突出《红色名录》编制的新工具和新方法, 并确定近期的保护优先事项, 这些保护优先事项同样适用于其他数据有限、生活史缓慢且面临高强度捕捞的水生类群。【翻译:胡怡思;审校:聂永刚】.
Fish-cubomedusa associations are less frequently reported than those involving scyphozoans and are typically limited to larval or juvenile fishes without an explicit predator context. Here, we report an adult Monodactylus argenteus associated with the cubozoan Morbakka sp. during an encounter with a carcharhinid shark at Magnetic Island, Australia. Throughout the observation, the fish maintained close association with the cubomedusa and reduced its distance to the bell and upper tentacle field during the shark encounter. Although behavioural motivations could not be determined from aerial observations alone, the observed change in spatial positioning by the fish was consistent with refuge use. This observation extends previous reports of fish-cubomedusa associations by documenting such an interaction in an adult fish during an encounter with a carcharhinid shark.