Here we review the literature on the basking shark (Cetorhinus maximus, Gunnerus, 1765), well known as the second largest extant shark (and fish) species globally. Previous reviews were published by Kunzlik in 1988 and Sims in 2008, but in the last 15 years modern electronic and DNA sequencing technologies have resulted in considerable advances in our knowledge of the species\' behaviour and ecology. Basking sharks are planktivores and under appropriate conditions spend prolonged periods at the ocean surface feeding on copepod prey that primarily make up their diet, the behaviour that gave rise to their common name. In general, they are migratory and move into higher latitude waters during the summer months, when loose surface-feeding aggregations may form at favoured sites, the best known of which at present occur at hotspots on the west coasts of Britain and Ireland. The species is found circumglobally in temperate waters, but they are also now known on occasion to migrate at depth between northern and southern hemispheres, as well as across oceans within the northern hemisphere. In the past basking shark were more abundant across much of their range, but, consequent on targeted fisheries and in some places intentional eradication, became everywhere scarce, with recent population recovery in the north-east Atlantic being the result of protective measures initiated in the 1990s. Despite their charismatic nature, some of their most fundamental biological processes including copulation, gestation and birth remain largely unknown, due to their migratory and often deep-water lifestyle. In contrast, the deployment of small-scale archival and satellite tags has revealed the details of both broadscale migratory movements and horizontal and vertical foraging behaviours. Recent genetic studies support evidence suggesting a degree of site fidelity in relation to seasonal feeding grounds, which likely explains why in the past local populations have collapsed following periods of intensive fishing. Other recent research using aerial drones and towed cameras has revealed within loose feeding aggregations elements of social behaviour that may have a courtship function as well as enhance feeding efficiency.

Polycyclic aromatic hydrocarbon (PAH) contamination is ubiquitous and comprises a significant worldwide concern in ecological and Public Health frameworks. Many aquatic biota representatives have been reported as contaminated by these toxic compounds, including one of the most threatened vertebrate groups, elasmobranchs (sharks and rays). Although elasmobranchs play important ecological roles and provide significant ecosystem services, they are highly consumed and comprise a cheap source of protein for humans globally. Studies concerning elasmobranch PAH contamination are, however, notably lacking. A systematic review was, thus, conducted herein to assess PAH elasmobranch contamination and discuss potential human health risks following the Preferred Reporting Item Statement Guidelines for Systematic Reviews and Meta-analyses (PRISMA) guidelines applying the Population (P), Intervention (I), Comparison I, and Outcome (O) (PICO) strategy. A total of 86 published papers were retrieved by this method and analyzed. Only nine studies of this total concerned PAH elasmobranch contamination, assessed in 10 shark species and one ray species, with only one study calculating human health risks. A significant knowledge gap is, thus, noted for this subject, indicating the need to monitor PAH elasmobranch contamination in consumed shark and ray species worldwide.

General anesthesia is often required in elasmobranch species for medical procedures. A variety of anesthetic drugs have been administered to elasmobranchs with wide variability in efficacy and safety. A retrospective review of 47 anesthetic procedures using IV propofol in eight different elasmobranch species at the Georgia Aquarium from 2010 to 2022 was performed. Cases involving seven sand tiger sharks (Carcharias taurus), four largetooth sawfish (Pristis perotteti), one longcomb sawfish (Pristis zijsron), four blacktip reef sharks (Carcharhinus melanopterus), three silvertip sharks (Carcharhinus albimarginatus), one sandbar shark (Carcharhinus plumbeus), five cownose rays (Rhinoptera bonasus), and one blotched fantail stingray (Taeniura meyeni) were evaluated. Induction dose of IV propofol (median: 2.5; 25-75%: 2.3-3.0; range: 1.7-4.0 mg/kg), time to desired effect (median: 4.0; 25-75%: 2.0-5.0; range: 0.5-15.0 min) and anesthetic duration (median: 76.0; 25-75%: 61.5-119.0; range: 27-216 min) were reported in all species. In six procedures (12.7%), maintenance of desired anesthetic plane required a supplemental dose of propofol IV (1 mg/kg) or addition of tricaine methanesulfonate (70 mg/L) as an immersion bath. The most common side effects were apnea and prolonged recovery. The IV propofol was efficacious and provided a procedural plane of anesthesia for a clinically relevant period of time in the majority of elasmobranch species, but observation for and management of complications is warranted.

Human activities have led to the loss of critical habitats for aquatic species at such an accelerated rate that habitat modification is considered a leading threat to biodiversity. Sharks and rays are considered the second most threatened group of vertebrates that have also suffered from habitat loss, especially in nursery grounds and reef-associated species. In this sense, actions toward the conservation of critical grounds for species survival are urgently needed, especially for those threatened with extinction. This study aimed to gather and provide information on the worldwide distribution and habitat association of the \'vulnerable\' Atlantic Nurse Shark Ginglymostoma cirratum through a literature review performed at the Dimensions research database. A total of 30 studies published between 1950 and 2021 were retained since they defined at least the type of habitat in which G. cirratum was associated. Most studies covered the Floridian ecoregion, where G. cirratum is more common and abundant. Reefs, seagrass, sandy, rocky, mangrove, and macroalgae accounted for the majority of habitat associations, with a higher diversity of habitats detected within marine protected areas (MPAs). Ginglymostoma cirratum was recorded at a maximum depth of 75 m, temperatures ranging from 25 °C to 34 °C, and salinities between 31 and 38 ppt. Neonates were associated with shallower habitats (<20 m), mostly reefs, rocks, macroalgae, sandy shores, and seagrass, in an average temperature of 26 °C and salinity of 36 ppt. Breeding events and habitats were reported by 11 studies, 72.7% of them in shallow waters, mostly inside MPAs (90.9%). Our findings highlighted the key role played by MPAs in protecting essential grounds for threatened species, such as the Atlantic Nurse Shark. Major ecoregions (e.g., the Eastern Atlantic) are still underrepresented in the scientific literature as long as studies aim specifically to assess G. cirratum habitat association. Thus, further insights into the essential habitats needed to conserve the Atlantic Nurse Shark can still emerge from future studies. Considering the recent IUCN extinction risk status change in G. cirratum (i.e., Data Deficient to \'Vulnerable\'), new conservation measures that integrate habitat protection and management are urgently needed and should consider the data collected herein.

Considerable research exists on the life history traits, evolutionary history, and environmental factors that shape the population genetic structure of marine organisms, including sharks and rays. Conservation concerns are particularly strong for this group as they are highly susceptible to anthropogenic stressors due to a combination of life history traits including late maturity and low fecundity. Here, we provide a review and synthesis of the global phylogeography of sharks and rays. We examined existing data for 40 species of sharks belonging to 17 genera and 19 species of rays belonging to 11 genera. Median joining haplotype networks were constructed for each species for the mtDNA cytochrome C oxidase subunit I (COI), and an Analysis of Molecular Variance (AMOVA) was conducted to understand patterns of genetic diversity and structure across the three major ocean basins-the Indian, Atlantic and Pacific Oceans. Haplotype networks showed very shallow coalescence in most species, a finding previously reported for marine teleosts. Star topologies were predominant among sharks while complex mutational topologies predominated among rays, a finding we attribute to extremely limited dispersal in the early life history of rays. Population structuring varied amongst species groups, apparently due to differences in life history traits including reproductive philopatry, site fidelity, pelagic habitat, migratory habits, and dispersal ability. In comparison to reef-associated and demersal species, pelagic and semi pelagic species showed lower levels of structure between and within ocean basins. As expected, there is variation between taxa and groups, but there are also some broad patterns that can guide management and conservation strategies.

Filter feeding elasmobranchs may be considered as biological indicators of marine pollution, despite most of these species are under some degree of extinction risk. Among threats to this taxonomic group, marine pollution might represent an additional concern for their survival. In this review, a comprehensive systematic search of scientific literature on pollutants in filter feeding elasmobranchs was conducted to evaluate the bioaccumulation patterns, and risk for human consumers. We found that, despite an increasing trend in the number of published studies, the geographical coverage is still very limited and most of the studies focused solely on trace elements (70.8%). Among sharks, Rhincodon typus was the most represented species (66.7%), while Mobula mobular the most studied ray species (41.7%). Comparing the levels of pollutants in filter feeders between ocean basins, this review highlighted that Hg, As and Cd levels are mostly higher in those areas affected by both strong natural and anthropogenic source of emissions, such as the Indian Ocean. With regards to OCs, ΣPCB levels in muscle of C. maximus were between 4.3 and 50.5 μg kg-1 ww, highlighting a persistent contamination of PCB in the Mediterranean Sea. Some species exceeded the maximum allowable limits for foodstuff consumption for As, Cd and Pb. A total of 77.8% of the analyzed species exceeded the Environmental Quality Standards for Hg, while they were always below the EQSbiota for HCB, PBDEs, PFOS and DDT. Given their feeding mechanism that continuously samples the marine environment, further investigations are urgently needed to determine not only the extent of contaminant exposure in different hotspot locations but also the risks posed to the elasmobranch health.

Anthropogenic activities contribute to nearly half of current Hg emissions to the atmosphere. In the marine habitat, oceanic predator fishes bioaccumulate Hg throughout their lives, making their consumption the main route of Hg exposure in humans. In this context, several publications, between 1973 and 2022, were selected, analyzed, and duly compiled, with the objective to investigate Hg contamination in nine species of bony fish: Thunnus thynnus (8 publications), Thunnus albacares (19), Thunnus obesus (7), Thunnus atlanticus (5), Thunnus alalunga (4), Katsuwonus pelamis (8), Xiphias gladius (18), Coryphaena hippurus (7) and Euthynnus alletteratus (4), as well as two species of cartilaginous fishes Prionace glauca (13 publications) and Isurus oxyrinchus (8). These studies totaled 5973 individuals. We classified species according to taxonomic groups and region of capture and found a significant difference between sharks and bony fishes, with higher Hg concentrations in sharks. The regions of occurrence were divided into 4 large areas (North Atlantic - NAO, South Atlantic - SAO, Equatorial Atlantic Ocean - EAO, and Mediterranean - MED), but no significant differences were observed when comparing the overall Hg concentrations in fish among regions (including all species). Additionally, a thorough discussion of the risks associated with human consumption of these species was conducted, as nine of the selected species presented individuals with Hg concentration values that exceeded the safety limits (1 ppm) set by health agencies worldwide.

450 million years of evolution have given chondrichthyans (sharks, rays and allies) ample time to adapt perfectly to their respective everyday life challenges and cognitive abilities have played an important part in that process. The diversity of niches that sharks and rays occupy corresponds to matching diversity in brains and behaviour, but we have only scratched the surface in terms of investigating cognition in this important group of animals. The handful of species that have been cognitively assessed in some detail over the last decade have provided enough data to safely conclude that sharks and rays are cognitively on par with most other vertebrates, including mammals and birds. Experiments in the lab as well as in the wild pose their own unique challenges, mainly due to the handling and maintenance of these animals as well as controlling environmental conditions and elimination of confounding factors. Nonetheless, significant advancements have been obtained in the fields of spatial and social cognition, discrimination learning, memory retention as well as several others. Most studies have focused on behaviour and the underlying neural substrates involved in cognitive information processing are still largely unknown. Our understanding of shark cognition has multiple practical benefits for welfare and conservation management but there are obvious gaps in our knowledge. Like most marine animals, sharks and rays face multiple threats. The effects of climate change, pollution and resulting ecosystem changes on the cognitive abilities of sharks and stingrays remain poorly investigated and we can only speculate what the likely impacts might be based on research on bony fishes. Lastly, sharks still suffer from their bad reputation as mindless killers and are heavily targeted by commercial fishing operations for their fins. This public relations issue clouds people\'s expectations of shark intelligence and is a serious impediment to their conservation. In the light of the fascinating results presented here, it seems obvious that the general perception of sharks and rays as well as their status as sentient, cognitive animals, needs to be urgently revisited.

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.

Recent shark attacks in New Caledonia have prompted local authorities to elaborate a risk-management plan. The objective of the present paper is to produce detailed data on shark attacks that occurred in New Caledonian waters for the last few decades, as well as on the injuries of the victims, in order to inform rescue and medical services as well as authorities in charge of educating the public and providing security.
Incidents involving sharks and humans in New Caledonia for the last six decades were included into a database. Sharks were tentatively identified to species according to the shape, size and other external characteristics of injuries to the victims, together with witness accounts. The severity of shark bites was evaluated against the scale proposed by A.K. Lentz and co-authors (Am Surg. 2010;76:101-6).
Sixty-seven shark-attack cases were recorded in New Caledonia from 1958 to 2020, of which 13 were lethal. The majority of the attacks concerned spearfishers and freedivers collecting invertebrates (58.5% of total). In the last decades, shark attacks may have increased towards bathers, swimmers and snorkelers (18.5%), and people taking part in water sports including surf, kitesurf, windsurf and SUP foil (14%). One scuba diver was also attacked (1.5%). Twenty attacks including 8 lethal ones were ascribed to the tiger shark Galeocerdo cuvier; 14 attacks including 2 lethal ones to the bull shark Carcharhinus leucas; 2 attacks including 1 lethal to the great white shark Carcharodon carcharías. The lethality of attacks was almost one in five, above the global average.
Feeding incentive appeared to be a frequent factor triggering attacks. The education of the public should be promoted as a preventive measure aiming to reduce the risk of such accidents.