The great hammerhead shark (Sphyrna mokarran) is a circumglobal species inhabiting warm temperate to tropical coastal waters. They are found over continental and insular shelves, as well as adjacent deep waters and are highly mobile and migratory. The general life history pattern of the great hammerhead is that of a long-lived (maximum estimated age 44 yrs), slow-growing, and late-maturing species. Observations and captures have been repeatedly and frequently documented at our study sites in Florida and the Bahamas. Our research combines telemetry and genetic data with modern analytical and ecological techniques to examine the conservation, habitat and space use of the endangered great hammerhead shark.
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Since its inception in 1990, the BBFSF has encountered great hammerhead sharks at various sites around South Bimini, and multi-year observations found that they show periodic high site fidelity at several locations surrounding the Bimini Islands. We have conducted research projects aimed to analyze the possible effects of food provisioning on their small-scale movements and the behavioural ecology, projects on their movement patterns and space use to determine regional connectivity between the US and Bahamas, vertical space usage, habitat use and predator/prey dynamics.
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An additional long term project (over the course of nearly a decade) is the development of an ID catalogue to monitor the population of sharks returning to Bimini each winter season. Through visual and photo ID, we have catalogued over 60 unique individual great hammerhead sharks in Bimini's small area. The sharks are identified through unique characteristics including fin notches, pigmentation spots, and ventral patterns.
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We are grateful to collaborate with local shark dive operator & crew from Neal Watson's Bimini Scuba Center in an effort to document all new and returning great hammerhead sharks seen in Bimini each year.
Conservation Importance
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Great hammerheads are a target or bycatch species in a wide variety of fisheries throughout their range and substantial population declines are suspected to have occurred in many areas as a result of fishing. They highly sought after because of their large fins which are prized in Hong Kong fish markets. Such declines and susceptibility have led to a global effort to enhance their management and conservation. In 2014 great hammerhead sharks were added to CITES (Convention on International Trade in Endangered Species) Appendix II and in 2018 were categorized as critically endangered by the IUCN (International Union for the Conservation of Nature) Red List. Great hammerheads are also listed on Annex I, Highly Migratory Species, of the UN Convention on the Law of the Sea, which urges States to cooperate over their management. NOAA Fisheries Service HMS Division has also identified Florida’s coastal waters as Essential Fish Habitat (EFH) for many species of sharks. This includes S. mokarran, which was recently added by the Florida Fish and Wildlife Conservation Commission (FWC) to the list of shark species prohibited from harvest in Florida state waters.
Unfortunately, great hammerhead sharks are not protected in US federal waters (just 3 nautical miles off Florida's shore on the Atlantic, and 9 nautical miles from shore on the Gulf). A stock assessment is currently underway in the US, with data from many collaborators being reviewed to determine the population status of these charismatic animals.