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| Sphyrna mokarran | |
|---|---|
| Name | Great hammerhead |
| Status | CR |
| Status system | IUCN3.1 |
| Genus | Sphyrna |
| Species | mokarran |
| Authority | Rüppell, 1837 |
Sphyrna mokarran
Sphyrna mokarran is a large requiem shark known as the great hammerhead, notable for a distinctive cephalofoil and apex predatory role. First described by Eduard Rüppell, it has been studied across marine research programs and cataloged by institutions such as the IUCN, NOAA, Smithsonian Institution, and various universities. The species features in conservation agendas involving NGOs, fisheries management bodies, and international agreements including CITES and regional fisheries commissions.
Originally described in the 19th century by Eduard Rüppell, the species was placed in the family Carcharhinidae and the genus Sphyrna. Taxonomic treatments have involved researchers from the Natural History Museum, London, the Smithsonian Institution, and taxonomists publishing in journals like Zoological Journal of the Linnean Society and Journal of Fish Biology. Molecular phylogenetics using samples analyzed in laboratories at Scripps Institution of Oceanography, University of Miami Rosenstiel School of Marine and Atmospheric Science, and Australian Institute of Marine Science have explored relationships among Sphyrna lewini, Sphyrna zygaena, Sphyrna tiburo, and other hammerhead taxa. Nomenclatural issues have been addressed in checklists by FishBase and catalogues maintained by the International Commission on Zoological Nomenclature.
The great hammerhead is characterized by a tall dorsal fin and an elongated, nearly straight anterior margin of the cephalofoil. Museum specimens in collections at the Natural History Museum, London, American Museum of Natural History, and Muséum national d'Histoire naturelle display size variation up to several meters, comparable to records from expeditions like those by Institute of Marine Research (Norway). Morphological descriptions reference works by ichthyologists associated with NOAA Fisheries, CSIRO Marine and Atmospheric Research, and university departments at University of California, Santa Barbara. Diagnostic features are cataloged in guides by FAO and regional field guides used by marine biologists in the Caribbean, Gulf of Mexico, West Africa, and Indo-Pacific.
The species occurs in tropical and subtropical coastal waters documented by surveys from NOAA National Marine Fisheries Service, the Australian Fisheries Management Authority, and regional agencies in Brazil, Mexico, South Africa, and India. Range maps in publications from IUCN and field surveys by Wildlife Conservation Society show presence in continental shelf habitats, coral reef systems monitored by Coral Reef Alliance, and mangrove-associated waters studied by The Nature Conservancy. Tagging studies conducted by teams at Monterey Bay Aquarium Research Institute, Tagging of Pacific Predators (TOPP), and universities in Hawaii and Mauritius indicate seasonal migrations tied to temperature gradients and prey distributions monitored by institutions like Woods Hole Oceanographic Institution.
Observational studies by researchers at Duke University Marine Lab, James Cook University, and regional marine institutes have documented solitary and transient schooling behavior. Interaction records with species cataloged by the IUCN SSC Shark Specialist Group include predation on batoids, competition with Carcharhinus leucas and life-history overlap with Alopias pelagicus. Ecological roles in reef ecosystems have been highlighted in studies by Reef Check, National Oceanic and Atmospheric Administration, and academic groups at University of Miami. Acoustic telemetry projects led by Florida Atlantic University and collaborative programs with Conservation International have elucidated site fidelity and habitat connectivity.
Stomach content analyses performed by teams at University of Southampton, University of Cape Town, and University of Queensland show a diet dominated by elasmobranchs, teleosts, and cephalopods. Bite mechanics and feeding ecology have been compared across hammerhead species in studies published in Proceedings of the Royal Society B and Journal of Experimental Biology by researchers affiliated with Harvard University, University of British Columbia, and Monash University. Observations from fisheries surveys in the Gulf of Aden, Mediterranean Sea, and Caribbean Sea corroborate opportunistic predation on rays and small sharks cataloged in regional checklists.
Reproductive biology has been studied by marine reproductive biologists at Florida State University, University of Florida, and University of Auckland; the species is viviparous with placental viviparity documented in comparative reviews by Oxford University Press and articles in Marine Biology. Litter size, gestation period, and size-at-birth estimates derive from data collected by regional fisheries agencies in Bahamas, Bahamas National Trust, and research stations affiliated with Smithsonian Tropical Research Institute. Juvenile habitat use in nurseries such as estuaries and seagrass beds has been reported by NOAA, Environment Agency Abu Dhabi, and regional conservation NGOs.
Assessed as Critically Endangered by the IUCN Red List, the species faces threats from commercial longline fisheries regulated by bodies including Regional Fisheries Management Organizations, targeted shark fisheries in West Africa and Southeast Asia, and bycatch recorded in data sets maintained by Sea Around Us and FAO. Conservation measures involve proposals to list the species under appendices of CITES, management recommendations from the IUCN SSC Shark Specialist Group, and national protections enacted by governments of The Bahamas, Australia, and South Africa. Advocacy and research support from NGOs such as World Wildlife Fund, Shark Trust, and Oceana complement scientific monitoring by universities and research institutes, while stock assessments rely on fisheries observers coordinated by organizations including Pew Charitable Trusts and regional fishery agencies.