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| Carcharhinus obscurus | |
|---|---|
| Name | Dusky shark |
| Status | Vulnerable |
| Status system | IUCN3.1 |
| Genus | Carcharhinus |
| Species | obscurus |
| Authority | (Lesueur, 1818) |
Carcharhinus obscurus is a large requiem shark commonly known as the dusky shark. It is recognized for its slow growth, late maturity, and migratory behavior, features that influence conservation status and management across jurisdictions such as United States, Australia, South Africa, Japan, and Brazil. The species figures in fisheries, research, and public policy discussions involving organizations like the IUCN, NOAA Fisheries, CSIRO, WWF, and the Convention on International Trade in Endangered Species of Wild Fauna and Flora.
Described by Charles Alexandre Lesueur in 1818, the species belongs to the family Carcharhinidae within the order Carcharhiniformes, a group that also includes taxa studied by institutions such as the Natural History Museum, London, the Smithsonian Institution, and the Australian Museum. Historical taxonomic treatments referenced works by Albert Günther, David Starr Jordan, and modern revisions published through journals affiliated with the Society for Marine Mammalogy and the American Fisheries Society. Molecular phylogenetics employing sequences compared in databases like those curated by the National Center for Biotechnology Information have clarified relationships among genera including Galeocerdo, Sphyrna, Prionace, Rhizoprionodon, and Negaprion.
Adults reach lengths typically between 2.5 and 3.2 m and mass exceeding 190 kg, with morphology described in field guides used by the Florida Fish and Wildlife Conservation Commission, Queensland Department of Agriculture and Fisheries, and the South African National Biodiversity Institute. Distinctive features include a long, rounded snout, large pectoral fins, and a dorsal fin base proportionally posterior compared with congeners noted in keys from the American Museum of Natural History and the Museum Victoria. Coloration is slate-gray dorsally and pale ventrally, a pattern referenced in identification manuals produced by NOAA, FAO, and the IUCN Shark Specialist Group. Dentition and vertebral counts used for species diagnosis are discussed in monographs by researchers at the University of Miami, Monterey Bay Aquarium Research Institute, and Scripps Institution of Oceanography.
The species has a circumglobal, warm-temperate to tropical distribution documented in regional checklists from Gulf of Mexico, Mediterranean Sea (occasional records), North Atlantic Ocean, South Atlantic Ocean, Indian Ocean, and western and eastern Pacific Ocean. Habitat associations include continental and insular shelves, embayments, and submarine canyon systems monitored by programs such as NOAA Fisheries' tagging initiatives, the Australian Institute of Marine Science, and the South African Department of Environment, Forestry and Fisheries. Seasonal migrations connect areas like the Gulf Stream, Agulhas Current, Kuroshio Current, and Brazil Current, with occupancy recorded from shallow coastal waters to depths exceeding 200 m during offshore movements cataloged by researchers at the Woods Hole Oceanographic Institution.
As an apex to mesopredator, it interacts with species documented in ecological studies by the Monterey Bay Aquarium Research Institute and universities including Duke University, University of California, Santa Barbara, and University of Cape Town. Diet studies referencing stomach content analyses from the NOAA Fisheries archives show predation on teleosts such as members of Scombridae, Sciaenidae, and Monacanthidae, as well as cephalopods and elasmobranchs reported in papers from the Journal of Fish Biology, Marine Biology, and Environmental Biology of Fishes. Movement ecology has been resolved using satellite tagging technology supplied by companies and programs such as Wildlife Computers and the Tagging of Pacific Predators (TOPP) project, revealing site fidelity to nursery areas monitored by regional agencies including the Florida Fish and Wildlife Conservation Commission and researchers affiliated with Duke University Marine Laboratory.
Reproduction is placental viviparous, a trait shared with congeners and detailed in reproductive studies from the South African Journal of Marine Science and theses held at University of Miami. Females bear litters typically of 1–12 pups after gestation periods estimated at 12 months or longer, parameters used by stock assessment teams at NOAA Fisheries and the International Commission for the Conservation of Atlantic Tunas for demographic modeling. Age and growth studies using vertebral band counts have been undertaken by scientists at Scripps Institution of Oceanography, CSIRO, and Woods Hole Oceanographic Institution, indicating sexual maturity in the mid-teens in years, with longevity estimates exceeding 40 years in some populations.
Threats include targeted and bycatch mortality in commercial and artisanal fisheries such as longline, gillnet, and trawl fleets operating under regulatory regimes of entities like the European Union, United States Department of Commerce, Australian Government Department of Agriculture, Water and the Environment, and regional bodies like the South Pacific Regional Fishery Management Organisation. The species is assessed as Vulnerable by the IUCN due to life-history vulnerability and documented population declines reported by initiatives including the Shark Conservation Fund and the Global Shark Trends Project. Conservation measures have been implemented via national protections, catch quotas, gear restrictions, and protected areas such as marine protected areas designated by NOAA National Marine Sanctuaries, Great Barrier Reef Marine Park Authority, and the South African National Parks system.
The species is significant for commercial fisheries targeting fins, meat, and liver oil, commodities traded in markets monitored by organizations such as CITES (through related listings), FAO, and national fisheries agencies. Bycatch reduction programs, observer schemes coordinated by the National Marine Fisheries Service and regional fisheries management organizations like the Inter-American Tropical Tuna Commission aim to mitigate mortality. Incidents involving humans draw attention from media outlets and stakeholders including Monterey Bay Aquarium, Shark Trust, and conservation NGOs such as Greenpeace and WWF, informing policy debates in legislative bodies like the United States Congress and parliaments of Australia and South Africa. Stock assessments and rebuilding plans are produced by panels of experts convened by the IUCN Shark Specialist Group, NOAA Fisheries, and academic collaborators at institutions such as Duke University and Scripps Institution of Oceanography.
Category:Marine fish