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Conservation Of Endangered Hammerheads

Overview:
The great hammerhead shark (Sphyrna mokarran) is a circumglobal species inhabiting warm temperate to tropical coastal waters. It occurs over continental and insular shelves, as well as adjacent deep waters and is thought to be highly mobile and migratory. The general life history pattern of S. mokarran is that of a long-lived (maximum estimated age 44 yrs), slow-growing, and late-maturing species. Observations and captures of S. mokarran have been repeatedly and frequently documented at our study sites in Florida and the Bahamas. Here we present a collaborative research project that 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.

Conservation Importance

S. mokarran 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. According to Clarke et al. (2006), hammerheads (Sphyrna spp.) are the second-most abundant species group in the international trade in fins. S. mokarran in particular are 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 March of this year S. mokarran were added to CITES (Convention on International Trade in Endangered Species) Appendix II and were categorized as endangered by the IUCN (International Union for the Conservation of Nature) Red List. S. mokarran 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. 

 

Clarke et al (2006) Global estimates of shark catches using trade records from commercial markets. Ecol Lett 9: 1115–1126.

Research Questions

1. Movement patterns

- Gain a better understanding of the horizontal and vertical use of space by S. mokarran at two locations. For example, do they show localised movements and/or travel long distances? Do S. mokarran in Bimini and Florida represent an interconnected population or distinct sub-populations?

- Determine the amount of time S. mokarran spend within the Bahamas EEZ vs. US EEZ?

 

2. Habitat preferences

- Determine to what extent abiotic factors, such as depth or temperature influence S. mokarran habitat usei.e. do they show thermal preferences, surface orientated or deep diving behaviors?

 

3. Conservation status

- Provide various stakeholders (e.g. National Marine Fisheries Service) within our study locations with new species-specific recommendations, that have direct application in future research and management approaches for this species locally and globally.