Fishing for oil and meat drives irreversible defaunation of deepwater sharks and rays.

The deep ocean is the last natural biodiversity refuge from the reach of human activities. Deepwater sharks and rays are among the most sensitive marine vertebrates to overexploitation. One-third of threatened deepwater sharks are targeted, and half the species targeted for the international liver-oil trade are threatened with extinction. Steep population declines cannot be easily reversed owing to long generation lengths, low recovery potentials, and the near absence of management. Depth and spatial limits to fishing activity could improve conservation when implemented alongside catch regulations, bycatch mitigation, and international trade regulation. Deepwater sharks and rays require immediate trade and fishing regulations to prevent irreversible defaunation and promote recovery of this threatened megafauna group.

First records of the Pacific sleeper shark Somniosus cf. pacificus in the western tropical Pacific.

Technological advances have enabled the expansion of ocean exploration to include the deep ocean, providing new species observations. Here, the authors present two new observations, captured by deep-sea cameras, of the sleeper shark Somniosus cf. pacificus from the Solomon Islands and Palau. This presents the first observation of S. cf. pacificus in the western Pacific tropics and extends its range about 2000 nautical miles south. The observations presented here provide much-needed information on the range of this species which can help guide future management and conservation actions.

Comparative analyses of the complete mitochondrial genomes of two southern African endemic guitarfish, Acroteriobatus annulatus and A. blochii.

Shark-like rays (order Rhinopristiformes) are among the most threatened cartilaginous fish globally. Despite this, unresolved taxonomic issues still exist within the group. To date, no studies have used complete mitochondrial genomes to assess the phylogenetic placement of Acroteriobatus within the non-monophyletic family Rhinobatidae. The current study reports the first complete mitochondrial genomes for Acroteriobatus annulatus and A. blochii. Similar to other rhinopristiforms, the complete sequences of A. annulatus (16,773 bp) and A. blochii (16,771 bp) were circular molecules with gene organisations identical to that of the typical vertebrate mitogenome. The A + T content was higher than the G + C content, with a bias towards A and C nucleotides observed in all complete mitogenomes. The stem-and-loop secondary structures of the putative origin of light-strand replication were found to have highly conserved synthesis and stem regions, with all substitutions and indels restricted to the loop structure. The ratios of non-synonymous to synonymous substitution rates indicated that purifying selection has been the dominant driver of evolution in rhinopristiform mitogenomes. Phylogenetic reconstructions placed Acroteriobatus as a sister-group to Rhinobatos, confirming its affiliation with the family Rhinobatidae. However, based on its apparent polyphyly with the aforementioned genera, the familial assignment of Pseudobatos is not fully resolved and requires further investigation.

Revision of the genus Centrophorus (Squaliformes: Centrophoridae): Part 3Redescription of Centrophorus uyato (Rafinesque) with a discussion of its complicated nomenclatural history.

Centrophorus uyato (Rafinesque, 1810) has a complicated nomenclatural history which has led to multiple scientific names being ascribed to this species. In the Mediterranean Sea, and elsewhere in its range, this species was previously referred to as C. granulosus (Bloch Schneider, 1801). The first paper in this revision series clarified that C. granulosus refers to a much larger species of gulper shark which attains at least 1.7 m length and is absent from the Mediterranean Sea. Further complicating the nomenclature of this species is the fact that the original description clearly refers to a Squalus species, and not a Centrophorus species. In this third part of the revision of the genus Centrophorus, this problematic species is redescribed. A detailed synonymy is provided and it is confirmed that C. machiquensis, C. bragancae and C. zeehaani are junior synonyms of this species. To preserve nomenclatural stability within the genus, the name Centrophorus uyato is retained for this species with a neotype from close to the original type locality off Italy being designated. Intraspecific variation within Centrophorus uyato is also discussed, particularly relating to denticle morphology and body morphology.

A taxonomic revision of Northeast Pacific softnose skates (Rajiformes: Arhynchobatidae: Bathyraja Ishiyama).

Softnose skates (Rajiformes: Arhynchobatidae: Bathyraja Ishiyama) are the most diverse skate genus, with 54 species, and are readily distinguishable from other genera in the family by their poorly calcified, flexible rostral cartilages. Six Bathyraja species are considered valid in the eastern North Pacific, including: B. abyssicola, B. aleutica, B. kincaidii, microtrachys, B. spinosissima, and B. trachura. Similar to other skate genera, eastern North Pacific Bathyraja lack a robust species-specific identification, which leads to issues with setting catch limits and creating management plans. This study identifies and formally redescribes the eastern North Pacific softnose skate species based on morphometric and meristic measurements and includes an Alaskan species, Bering Skate, B. interrupta due to its close morphological relationship to B. kincaidii. A lectotype for B. interrupta is designated. Multivariate tests determined that significant differences existed between the study species. Parsimonious phylogenetic trees showed that B kincaidii represents the basal condition, with B. abyssicola and B. aleutica being the most derived species in the study. The formerly synonymized species B. interrupta and B. kincaidii were shown to be separate, as were the previously synonymized species B. microtrachys and B. trachura. Improved Bathyraja species identification will hopefully assist fisheries managers in developing conservation policies easing the impacts of deep-sea fishing expansion.

Overfishing drives over one-third of all sharks and rays toward a global extinction crisis.

The scale and drivers of marine biodiversity loss are being revealed by the International Union for Conservation of Nature (IUCN) Red List assessment process. We present the first global reassessment of 1,199 species in Class Chondrichthyes-sharks, rays, and chimeras. The first global assessment (in 2014) concluded that one-quarter (24%) of species were threatened. Now, 391 (32.6%) species are threatened with extinction. When this percentage of threat is applied to Data Deficient species, more than one-third (37.5%) of chondrichthyans are estimated to be threatened, with much of this change resulting from new information. Three species are Critically Endangered (Possibly Extinct), representing possibly the first global marine fish extinctions due to overfishing. Consequently, the chondrichthyan extinction rate is potentially 25 extinctions per million species years, comparable to that of terrestrial vertebrates. Overfishing is the universal threat affecting all 391 threatened species and is the sole threat for 67.3% of species and interacts with three other threats for the remaining third: loss and degradation of habitat (31.2% of threatened species), climate change (10.2%), and pollution (6.9%). Species are disproportionately threatened in tropical and subtropical coastal waters. Science-based limits on fishing, effective marine protected areas, and approaches that reduce or eliminate fishing mortality are urgently needed to minimize mortality of threatened species and ensure sustainable catch and trade of others. Immediate action is essential to prevent further extinctions and protect the potential for food security and ecosystem functions provided by this iconic lineage of predators.

An annotated checklist of the chondrichthyans of South Africa.

An annotated checklist of chondrichthyan fishes (sharks, batoids, and chimaeras) occurring in South African waters is presented. The checklist is the result of decades of research and on-going systematic revisions of the regional fauna. The chondrichthyan fauna of South Africa is one of the richest in the world with 191 species, comprising 50 families and 103 genera. It consists of 30 families, 64 genera, and 111 species of sharks; 17 families, 36 genera, and 72 species of batoids; and, 3 families, 5 genera, and 8 species of chimaeras. The most species-rich shark families are the whaler sharks Carcharhinidae with 20 species followed by the deepwater catsharks Pentanchidae with 13 species. The most species-rich batoid families are the hardnose stakes Rajidae with at least 21 species followed by the stingrays Dasyatidae with 13 species. This monograph represents the first detailed annotated checklist of chondrichthyans from South Africa in over 30 years.

Leucoraja elaineae sp. nov., a new rough skate (Rajiformes: Rajidae) from the Western Indian Ocean.

A new species of the genus Leucoraja is described from off Kenya in the Western Indian Ocean (WIO). The new species was collected during a survey of the R/V Fridtiof Nansen. Leucoraja elaineae sp. n. is the third species in the genus found to occur in the WIO, and the only species in the genus Leucoraja known exclusively from this region. Its closest geographic congener L. wallacei, occurring from Namibia to southern Mozambique, can be separated by a combination of morphological and meristic characters including an elongated, pronounced snout (L. elaineae sp. n.) vs a short, blunt snout (L. wallacei), higher predorsal vertebral (107 vs 64-74) and pectoral fin radial counts (77 vs 61-64), a dorsal surface pattern consisting of a single ocelli at the midbase of each pectoral fin, paired small white spots, and no banding or crossbars on its tail vs numerous rosettes and whorls, no prominent ocelli at the pectoral fin bases, and 3-4 tail bands. The only other WIO Leucoraja species in the genus, L. compagnoi is known only from South Africa and has a short, blunt snout, a lower upper tooth count (38 vs 57 in L. elaineae sp. n.), a plain dorsal disc color with no markings and distinct bands on its tail. All other members of the genus occur in the North Atlantic, except one species that occurs in the eastern Central Atlantic and one in the eastern Indian Ocean.

Redescription and taxonomic status of Dipturus chilensis (Guichenot, 1848), and description of Dipturus lamillai sp. nov. (Rajiformes: Rajidae), a new species of long-snout skate from the Falkland Islands.

Recent molecular evidence has called into question the identity of skates collected in the waters off the Falkland Islands previously identified as Zearaja chilensis. NADH2 sequence data indicate that these specimens are not conspecific with those currently referred to as Z. chilensis from Chile and, in fact, represent a novel cryptic species. This study aimed to investigate this hypothesis based on morphological comparisons of specimens from the coasts of both western and eastern South America. In total, 50 specimens from Chile and 41 specimens from the Falkland Islands were collected and examined; morphometric data were generated for a subset of specimens from both areas. NADH2 sequence data were generated for a total of 19 specimens from both areas, as well as specimens of Z. nasuta from New Zealand, D. pullopunctatus from South Africa, D. oxyrinchus from the Azores, Okamejei hollandi, and O. cairae from Borneo, and O. kenojei from Japan. Based on morphological and molecular analyses, Zearaja is synonymized with Dipturus and species assigned to the former genus are transferred to the latter genus. A neotype is designated for D. chilensis and this species is redescribed. Dipturus lamillai sp. nov. is described based on specimens from the Falkland Islands. Comparison of our NADH2 data with data for mitochondrial genomes generated from tissue samples taken from two specimens originally identified as Z. chilensis, indicate that, while the sample from Chile came from a specimen of D. chilensis, that from the skate steak obtained from a restaurant in Korea actually came from a specimen of D. lamillai sp. nov. This emphasizes the importance of confirming both the provenance and identity of specimens from which sequence data are generated and submitted to GenBank if misidentifications are to be avoided.

New insights into the identities of the elasmobranch fauna of Sri Lanka.

Identities of elasmobranchs from Sri Lanka encountered during collections conducted in an intensive nine-day survey of fish markets and landing sites at 11 localities in the North Western, Northern, and Eastern Provinces in March of 2018 were assessed. In total, 111 specimens representing 34 elasmobranch species were examined. Sequence data for the NADH2 gene were generated for all specimens. Independent Neighbor-Joining analyses, which included data for related taxa, were conducted for 25 subgroups of elasmobranchs to help confirm specific identifications. Five of the 34 species encountered are likely new to science. These consist of one species each of the batoid genera Brevitrygon, Narcine, and Torpedo, and the selachian genera Centrophorus, and Chiloscyllium. The specific identities of 12 species previously known to occur in Sri Lanka are updated to conform to current taxonomy; four of these (Gymnura cf. poecilura 2, Carcharhinus cf. limbatus, Echinorhinus sp. 1, and Iago cf. omanensis 1) represent what appear to be undescribed species reported previously from other localities. Three species (Maculabatis arabica, Acroteriobatus variegatus, and Centroscymnus owstonii) are reported from Sri Lanka for the first time; the latter species also represents the first documented record of this genus and family for the island nation. One of the two specimens on which the recent description of the new species of Planonasus indicus was based was also collected as part of this survey. Although some of the species confirmed to occur in Sri Lanka have also been found in India, others were previously known only from the Persian Gulf, Gulf of Oman, or localities in Southeast Asia. The high amount of novelty discovered as a result of a survey of such short duration emphasizes the importance of more intensive survey efforts in this region now that the civil unrest that precluded such work for nearly three decades has come to an end.

Etmopterus marshae sp. nov, a new lanternshark (Squaliformes: Etmopteridae) from the Philippine Islands, with a revised key to the Etmopterus lucifer clade.

A new species of lanternshark, Etmopterus marshae (Squaliformes: Etmopteridae), is described from the Philippine Islands, western North Pacific Ocean. The new species occurs along insular slopes at a depth range of 322-337 m. The new species resembles other members of the "Etmopterus lucifer" clade in having linear rows of dermal denticles, and most closely          resembles E. burgessi from Taiwan and E. evansi and E. pycnolepis from the South Pacific. It can be distinguished from all other members of the E. lucifer clade by a combination of characteristics, including length of anterior and posterior flank branches being of relatively equal length, straight vs. curved anterior flank marking, relative lengths of caudal markings,     coloration, and relatively small size. A revised key to the revised key to the Etmopterus lucifer clade is provided.

Parmaturus nigripalatum n. sp., a new species of deep-sea catshark (Chondrichthyes: Carcharhiniformes: Scyliorhinidae) from Indonesia.

Parmaturus nigripalatum, a new species of catshark of the genus Parmaturus is described from a single specimen collected from a deep-water shark longliner operating in south Sumbawa waters, Indonesia. This new species is distinguished from its closest geographic congener P. lanatus by having prominent enlarged caudal crests, well-developed labial furrows with the uppers and lowers of equal lengths, mouth roof blackish with dark pores, first dorsal fin origin more posteriorly positioned on body trunk, and much lower tooth counts than all other known Parmaturus species. This is the second Parmaturus species recorded from Indonesian waters.

Revision of the genus Centrophorus (Squaliformes: Centrophoridae): Part 2-Description of two new species of Centrophorus and clarification of the status of Centrophorus lusitanicus Barbosa du Bocage & de Brito Capello, 1864.

Centrophorus specimens with a distinctive long-based first dorsal fin (long-finned species) have previously been considered to be Centrophorus lusitanicus first described from Portugal. Critical examination of the original description and illustration reveal that C. lusitanicus should be considered a junior synonym of C. granulosus. However, the specimen considered to be the syntype of C. lusitanicus in the Natural History Museum in London is clearly a long-finned species and not conspecific with C. granulosus. A more detailed investigation revealed that this specimen should not be considered a syntype and was likely not originally collected off the coast of Portugal. Investigation of long-finned specimens of Centrophorus from the Indo-West Pacific and Eastern Atlantic revealed that two undescribed species exist and are herein formally described as C. lesliei and C. longipinnis. The two species are similar morphologically and belong to the long-snout Centrophorus group (e.g. C. isodon and C. harrissoni) but are clearly separable based on their very long first dorsal fins. The two species differ in relative length of the first dorsal fin and several other characters. They also differ genetically. Nonmetric multidimensional ordination based on morphometric data reveals both species level and ontogenetic differences. A short erratum is also provided for Part 1 of this revision of the Centrophorus due to two figure related errors which may cause some confusion.

Age and Growth of Elasmobranchs and Applications to Fisheries Management and Conservation in the Northeast Pacific Ocean.

In addition to being an academic endeavour, the practical purpose of conducting age and growth studies on fishes is to provide biological data to stock assessment scientists and fisheries managers so they may better understand population demographics and manage exploitation rates. Age and size data are used to build growth models, which are a critical component of stock assessments. Though age determination of elasmobranchs in the northeast Pacific Ocean (NEP) began in the 1930s, the field has evolved substantially in recent years, allowing scientists to incorporate age data into assessments for more species than ever before. Owing to the highly diverse biology of this group of fishes, each species has its own set of challenges with regard to age determination. Age determination methods typically rely on semicalcified hard structures that form regular growth patterns; however, the structure selected and preparation method used is often species specific. New staining techniques have improved the ability to assess age and improve ageing precision for some species, and advances in microchemical methods have allowed for independent means of estimating age and validating age determination accuracy. Here we describe current age determination methods for NEP elasmobranchs. While the library of available techniques is increasing, there are still some NEP species for which reliable ageing methods have yet to be defined; we discuss these challenges and potential avenues of future research. Finally, we conclude by describing how age estimates are used in growth models and subsequently in stock assessments of selected NEP elasmobranchs.

Biodiversity, Life History, and Conservation of Northeastern Pacific Chondrichthyans.

The sharks, batoids, and chimaeras, collectively the class Chondrichthyes, are one of the most successful groups of fishes, with over 1250 species globally. Recent taxonomic revisions have increased their diversity by about 20% over the past 17 years (2000-2016). The Northeast Pacific Ocean is one of the top 20 most diverse regions/countries on the globe with 77 chondrichthyan species, a number less than a quarter that of the most species-rich area (Australia) but that has increased by 10% since 2000 to include three new species (two skates and a chimaera). In this chapter we discuss the species richness of chondrichthyans occurring in the Northeast Pacific Ocean, characterize their life histories, briefly review several fisheries, and summarize the conservation status of those chondrichthyans occurring in the region. Detailed descriptions and evaluations of fisheries can be found in Chapter 7 of AMB Volume 78.

Etmopterus samadiae n. sp., a new lanternshark (Squaliformes: Etmopteridae) from Papua New Guinea.

A new species of lanternshark, Etmopterus samadiae (Squaliformes: Etmopteridae), is described from off northern Papua New Guinea, in the western Central Pacific Ocean. The new species resembles other members of the "Etmopterus lucifer" clade in having linear rows of dermal denticles and most closely resembles E. brachyurus from the western North Pacific. The new species occurs along insular slopes between 340 and 785 m depth. The new species can be distinguished from other members of the E. lucifer clade by a combination of characteristics, including length of anterior flank branch markings being slightly shorter than its posterior branch, a longer caudal base marking, and irregular and variable number of black, horizontal, dash-like marks on sides of body. Molecular analysis based on the NADH2 marker further supports the distinction of E. samadiae from other members of the E. lucifer clade.

Rhinobatos austini n. sp., a new species of guitarfish (Rhinopristiformes: Rhinobatidae) from the Southwestern Indian Ocean.

Rhinobatos austini sp. n. is described from the southwestern Indian Ocean based on four specimens collected from the KwaZulu-Natal Province, South Africa and from Mozambique. The new species, with one exception, can be distinguished from all other members of this genus by a prominent teardrop-shaped dark blotch on the ventral surface of its snout. Its closest congener, R. holcorhynchus, also has a prominent teardrop-shaped blotch on its snout, but the new species differs from it by a lack of prominent thorns and tubercles on it dorsal disc surface and a very striking dorsal surface colour pattern of paired spots, some forming darker transverse bands across its back. Geographically, these two species broadly overlap, but R. austini appears to be a shallow, more coastal species (<1-107 m) compared to R. holcorhynchus that has a mostly offshore (75-254 m) depth distribution.

An evaluation of mercury offloading in two Central California elasmobranchs.

Elasmobranchs occupy high trophic levels, accumulate high concentrations of mercury in their tissues, and have high energetic levels of maternal investment to offspring, which may cause embryos to be exposed in utero to harmful concentrations of mercury. We investigated the maternal transfer of mercury in two common coastal elasmobranch species, Triakis semifasciata and Platyrhinoidis triseriata, to determine which reproductive parameters may influence mercury offloading, and whether embryos are at risk to mercury toxicity. Mercury concentration was measured in female muscle, female liver, and embryonic tissues. The behavior of mercury in adult female tissues differed between species, as liver mercury concentration was significantly correlated to muscle mercury concentration in P. triseriata but not in T. semifasciata. Embryos of both species were found with potentially harmful mercury concentrations in their muscle tissues. Embryo mercury concentration increased with female muscle mercury concentration, but the relationship to female liver mercury was more variable. The rate of mercury transfer and overall offloading potential were significantly greater in P. triseriata than T. semifasciata. It appears that female mercury concentration, either in muscle or liver, is an important influencing factor for mercury offloading, but the impact of the differing reproductive modes in these two species was less clear. More study on this subject will continue to elucidate the factors influencing mercury offloading in sharks and rays, and how contaminant risk affects populations on a whole.