When sharks nearly disappeared

Each year, the discovery of new shark species underscores how little we know about ocean biodiversity (1). This is alarming not only because human pressures threaten sharks more than other marine lineages (2) but also because their fossil record suggests that they were largely resilient to extinction in the past (3), with some extant species persisting for tens of million years (4). On page 1105 of this issue, Sibert and Rubin (5) report an unexpected finding: a wholesale extinction of shark lineages in the pelagic ocean, the largest ecosystem on Earth, about 19 million years ago. Their discovery suggests that some extinctions in the open sea of the past may have been cryptic. More puzzling is that this event in the early Miocene seems to have been hiding in an interval of geologic time that was previously unremarkable. How did they find it, and what does it mean? Our view of the ancient oceans is constrained by the environments recorded in the rock record, which are often limited to shallow-water deposits that provide little insight into the ocean-wide history of pelagic faunas. The study of Sibert and Rubin takes advantage of a system that Sibert largely pioneered (6) using ichthyoliths—tiny, hard bits of shark skin and bony fish teeth that naturally fall from their bodies to the seafloor. Once retrieved from deep-sea sediment drill cores (about 5700 m deep), these microscopic fossils provide a rich record of ancient oceanic shark (those living in the open ocean) ecomorphotypes and their abundance, all accumulating in fine succession at the scale of thousands of years. Although this proxy record of diversity has weak phylogenetic control because such samples of skin and teeth do not always correspond directly with host lineages, its power derives from the high temporal resolution and broad geographic coverage that comes with sediment cores. By using cores from multiple regions, the diversity patterns from the microfossils of marine fauna can yield major insights into evolution of the open sea that would be otherwise unknown

Galeorhinus galeus, Tope

Tope (Galeorhinus galeus) is a medium-sized (to 200 cm total length) bentho-pelagic shark, widespread in temperate waters in most oceans. It is present across the Northeast, Eastern Central, Southwest, and Southeast Atlantic, the Mediterranean Sea, the Eastern Indian, and across all of the Pacific, except in the Northwest Pacific. It occurs on continental shelves and upper to mid slopes from shallow inshore to well offshore to depths of 826 m, though most frequently to depths of 200 m. Genetic and tagging data support up to six separate subpopulations of Tope and while the species makes extensive movements within each of the subpopulations, there is no evidence of mixing between them. Tope has a particularly low biological productivity with a late age-at-maturity and triennial reproductive cycle. It is caught globally as target and bycatch in industrial and small-scale demersal and pelagic gillnet and longline fisheries, and to a lesser extent in trawl and hook-and-line fisheries. Tope is often retained for the meat and fins but is discarded or released in some areas, in line with regional management measures. Steep subpopulation and stock reductions of >80% over the past three generation lengths (79 years) have occurred in the Southwest Atlantic, southern Africa, and Australia. In the Northeast Atlantic, the subpopulation is estimated to have undergone a reduction of 76% over the past three generation lengths (79 years). The New Zealand stock is estimated to have undergone a reduction of 30?49% over the past three generation lengths (79 years). In the Northeast Pacific, a dramatic decline in the subpopulation occurred in the early 1940s, with no recovery until 1997?2004 when localized management led to a localized increase in abundance. The consistent steep subpopulation reductions across most of the analyzed subpopulations and stocks together with the lack of movement between the subpopulations are cause for serious concern. Management in Australia, probably aided by the immigration of large mature animals from New Zealand, appears to have stabilized that stock since 2000. The subpopulation in the Northeast Atlantic has been stable in recent years, possibly due to management measures, and there is some recovery in part of the Northeast Pacific. Release of this species is mandatory since 2011 off Canada. Release is mandatory in European Union waters for line-caught Tope. The global population is estimated to have undergone a reduction of 88% with the highest probability of >80% reduction over the last three generations (79 years) due to levels of exploitation, and Tope is assessed as Critically Endangered A2bd.Fil: Walker, T. I.. University of Melbourne; AustraliaFil: Rigby, C. L.. James Cook University; AustraliaFil: Pacoureau, N.. University Fraser Simon; CanadáFil: Ellis, J.. No especifíca;Fil: Kulka, D. W.. No especifíca;Fil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Herman, K.. Georgia Aquarium; Estados Unido

Sharkipedia: Elasmobranch Traits and Trends Global Database

Sharkipedia is an open source research initiative to make all published biological traits and population trends on sharks, rays, and chimaeras accessible to everyone. Originally inspired by FishBase, our databases are modelled after Coral Traits database and the RAM legacy database. The key aspects of our initiative were established with the central tenet of facilitating research on chondrichthyans, and are built on three main principles: (1) being completely web-based open- access and queryable for use by all researchers, (2) quality control and assurance by experts in the field and traceability of every measurement to its original references, and (3) regular updates association with International Union for the Conservation of Nature (IUCN) Red List Assessment workshops of focal species

Squalus acanthias, spiny dogfish

While there are reported subpopulations of Squalus acanthias (Linnaeus, 1758) elsewhere in the world, the North Pacific subpopulation is now considered a separate species, Squalus suckleyi (Girard, 1854) (see Ebert et al. 2010). Further taxonomic studies on this genus are required, including in relation to Mediterranean and Black Sea subpopulations. In Europe, three subpopulations are inferred to occur.Fil: Finucci, B.. National Institute of Water and Atmospheric Research; Nueva ZelandaFil: Cheok, J.. University Fraser Simon; CanadáFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". Estación Hidrobiológica de Puerto Quequén (sede Quequén); ArgentinaFil: Cotton, C. F.. Florida State University; Estados UnidosFil: Dulvy, N. K.. University Fraser Simon; CanadáFil: Kulka, D. W.. No especifíca; ArgentinaFil: Neat, F. C.. No especifíca; ArgentinaFil: Pacoureau, N.. University Fraser Simon; CanadáFil: Rigby, C. L.. James Cook University; AustraliaFil: Tanaka, S.. No especifíca; ArgentinaFil: Walker, T. I.. University of Melbourne; Australi

Conservation successes and challenges for wide-ranging sharks and rays

Overfishing is the most significant threat facing sharks and rays. Given the growth in consumption of seafood, combined with the compounding effects of habitat loss, climate change, and pollution, there is a need to identify recovery paths, particularly in poorly managed and poorly monitored fisheries. Here, we document conservation through fisheries management success for 11 coastal sharks in US waters by comparing population trends through a Bayesian state-space model before and after the implementation of the 1993 Fisheries Management Plan for Sharks. We took advantage of the spatial and temporal gradients in fishing exposure and fisheries management in the Western Atlantic to analyze the effect on the Red List status of all 26 wide-ranging coastal sharks and rays. We show that extinction risk was greater where fishing pressure was higher, but this was offset by the strength of management engagement (indicated by strength of National and Regional Plan of Action for sharks and rays). The regional Red List Index (which tracks changes in extinction risk through time) declined in all regions until the 1980s but then improved in the North and Central Atlantic such that the average extinction risk is currently half that in the Southwest. Many sharks and rays are wide ranging, and successful fisheries management in one country can be undone by poorly regulated or unregulated fishing elsewhere. Our study underscores that well-enforced, science-based management of carefully monitored fisheries can achieve conservation success, even for slow-growing species

Myliobatis freminvillii, bullnose eagle ray

The Bullnose Eagle Ray (Myliobatis freminvillii) is a medium-sized (to 106 cm disc width) demersal coastal eagle ray that occurs in the Northwest, Western Central, and Southwest Atlantic Oceans from Massachussetts, USA to the Texas coast of the Gulf of Mexico and from Venezuela to Buenos Aires, Argentina and inhabits continental shelves from the surface to a depth of 122 m. Its is captured by artisanal longlines, gillnets, beach seines and also in industrial shrimp trawls. In the Northwest Atlantic, population trend data are available from a deep-water trawl survey in the northern Gulf of Mexico that reveal steep increases in abundance over 2002-2013. There are no known threats in the Northwest and Western Central Atlantic, but in the Southwest Atlantic artisanal fisheries are intense. Further, there are largely unmanaged commercial trawl and longline fisheries in this area. This inshore eagle ray is exposed to intense and often unmanaged fishing pressure throughout the Southwest Atlantic portion of its range, and it has no refuge at depth. Due to the level of exploitation by widespread artisanal fisheries which lack adequate management, it is suspected that this species has undergone a population reduction of >80% over the past three generation lengths (44 years) in the Atlantic South American part of its range, but is stable in the Northwest and Western Central Atlantic. Overall, based on its range, with almost all threats found in the Southwest Atlantic, and the suspected low productivity of the species, the Bullnose Eagle Ray is suspected to have undergone a population reduction of 30-49% in the past three generation lengths (44 years) due to levels of exploitation, and it is assessed as Vulnerable A2bd.Fil: Carlson, J.. National Marine Fisheries Service; Estados UnidosFil: Charvet, P.. Universidade Federal do Paraná; BrasilFil: Avalos, C.. Fundacion Mundo Azul; GuatemalaFil: Blanco Parra, M. P.. Universidad de Quintana Roo; MéxicoFil: Briones Bell lloch, A.. Direccion de Regulaciones Pesqueras y Ciencias; CubaFil: Cardeñosa, D.. Florida International University; Estados UnidosFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". Estación Hidrobiológica de Puerto Quequén (sede Quequén); ArgentinaFil: Cuevas, J.M.. Wildlife Conservation Society; Estados UnidosFil: Derrick, D.. University Fraser Simon; CanadáFil: Espinoza, E.. Direccion Parque Nacional Galapagos; EcuadorFil: Mejía Falla, P. A.. Wildlife Conservation Society; Estados UnidosFil: Morales Saldaña, J. M.. Smithsonian Tropical Research Institute; PanamáFil: Motta, F.. Universidade Federal de Sao Paulo; BrasilFil: Naranjo Elizondo, B.. Universidad de Costa Rica; Costa RicaFil: Pacoureau, N.. University Fraser Simon; CanadáFil: Paesch, L.. Dirección Nacional de Recursos Acuáticos; UruguayFil: Perez Jiménez, J. C.. El Colegio de la Frontera del Sur; MéxicoFil: Rincon, G.. Universidade Federal Do Maranhao.; BrasilFil: Schneider, E. V. C.. Cape Eleuthera Institute; BahamasFil: Simpson, N. J.. Salvageblue; San Vicente y las GranadinasFil: Talwar, B. S.. Florida International University; Estados UnidosFil: Pollom, R.. University Fraser Simon; Canad

Myliobatis goodei, southern eagle ray

The Southern Eagle Ray (Myliobatis goodei) is a medium-sized (to at least 115 cm DW) coastal eagle ray that occurs in the Western Central and Southwest Atlantic Oceans from South Carolina and Florida, USA and Quintana Roo, Mexico to San Jorge Gulf, Santa Cruz, Argentina. It inhabits continental shelves from inshore to depths of 181 m. It is captured using artisanal longlines, gillnets, beach seines, and in industrial shrimp trawls. This species is inferred to be stable or increasing in the Western Central Atlantic, based on its similarity to the Bullnose Eagle Ray (Myliobatis freminvillei). In the Southwest Atlantic artisanal fisheries are intense, further there are largely unmanaged commercial trawl and longline fisheries in many areas. In Brazil, landings of eagle rays have been reduced by 60% over 2000?2012 in Santa Catarina State, and a reduction of 91% in Rio Grande do Sul since the 1980s. This inshore eagle ray has no refuge at depth and is exposed to intense and often unmanaged fishing pressure throughout the Atlantic South American portion of its range and there it is suspected that this species has undergone a population reduction of >80% over the past three generation lengths (44 years), but is stable in the Western Central Atlantic. Overall, based its range with the almost all threats found in the Southwest Atlantic, the suspected low productivity of the species, this species is suspected to have undergone a population reduction of 30 49% in three generation lengths (44 years) due to levels of exploitation, and it is assessed as Vulnerable A2d.Fil: Carlson, J.. National Marine Fisheries Service; Estados UnidosFil: Charvet, P.. Universidade Federal do Paraná; BrasilFil: Avalos Castillo, C.. Fundación Mundo Azul; GuatemalaFil: Blanco Parra, M. P.. Universidad de Quintana Roo; MéxicoFil: Briones Bell lloch, A.. Dirección de Regulaciones Pesqueras y Ciencias; CubaFil: Cardeñosa, D.. Florida International University; Estados UnidosFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". Estación Hidrobiológica de Puerto Quequén (sede Quequén); ArgentinaFil: Cuevas, J.M.. Wildlife Conservation Society; Estados UnidosFil: Derrick, D.. University Fraser Simon; CanadáFil: Espinoza, E.. Galapagos National Park Directorate; EcuadorFil: Mejía Falla, P. A.. Wildlife Conservation Society; Estados UnidosFil: Morales Saldaña, J. M.. Smithsonian Tropical Research Institute; PanamáFil: Motta, F.. Universidade Federal Do Sao Paulo; BrasilFil: Naranjo Elizondo, B.. Universidad de Costa Rica; Costa RicaFil: Pacoureau, N.. University Fraser Simon; CanadáFil: Paesch, L.. Direccion Nacional de Recursos Acuaticos ; UruguayFil: Pérez Jiménez, J. C.. El Colegio de la Frontera del Sur; MéxicoFil: Rincon, G.. Universidade Federal Do Maranhao.; BrasilFil: Schneider, E. V. C.. Cape Eleuthera Institute; BahamasFil: Simpson, N. J.. Salvageblue; San Vicente y las GranadinasFil: Talwar, B. S.. Florida International University; Estados UnidosFil: Pollom, R.. University Fraser Simon; Canad

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

Estimating IUCN Red List Population Reduction: JARA—A Decision-Support Tool Applied to Pelagic Sharks

The International Union for Conservation of Nature\u27s (IUCN) Red List is the global standard for quantifying extinction risk but assessing population reduction (criterion A) of wide‐ranging, long‐lived marine taxa remains difficult and controversial. We show how Bayesian state–space models (BSSM), coupled with expert knowledge at IUCN Red List workshops, can combine regional abundance data into indices of global population change. To illustrate our approach, we provide examples of the process to assess four circumglobal sharks with differing temporal and spatial data‐deficiency: Blue Shark (Prionace glauca), Shortfin Mako (Isurus oxyrinchus), Dusky Shark (Carcharhinus obscurus), and Great Hammerhead (Sphyrna mokarran). For each species, the BSSM provided global population change estimates over three generation lengths bounded by uncertainty levels in intuitive outputs, enabling informed decisions on the status of each species. Integrating similar analyses into future workshops would help conservation practitioners ensure robust, consistent, and transparent Red List assessments for other long‐lived, wide‐ranging species

Half a century of global decline in oceanic sharks and rays

This is the author accepted manuscript. The final version is available from Nature Research via the DOI in this recordData availability: Data are available on https://www.sharkipedia.org/ and at https://doi.org/10.5281/zenodo.4135325. Source data are provided with this paper.Overfishing is the primary cause of marine defaunation, yet declines in and increasing extinction risks of individual species are difficult to measure, particularly for the largest predators found in the high seas. Here we calculate two well-established indicators to track progress towards Aichi Biodiversity Targets and Sustainable Development Goals: the Living Planet Index (a measure of changes in abundance aggregated from 57 abundance time-series datasets for 18 oceanic shark and ray species) and the Red List Index (a measure of change in extinction risk calculated for all 31 oceanic species of sharks and rays). We find that, since 1970, the global abundance of oceanic sharks and rays has declined by 71% owing to an 18-fold increase in relative fishing pressure. This depletion has increased the global extinction risk to the point at which three-quarters of the species comprising this functionally important assemblage are threatened with extinction. Strict prohibitions and precautionary science-based catch limits are urgently needed to avert population collapse, avoid the disruption of ecological functions and promote species recovery.Shark Conservation FundUS National Science FoundationAustralian Government National Environmental Science ProgramNatural Science and Engineering Research CouncilCanada Research Chairs Progra