Overview

Adequate conservation and management of shark populations is becoming increasingly important on a global scale with declines documented worldwide. Successful management of these species requires detailed information on their movement and distributions. However, generating such information for large-bodied sharks is challenging, as they typically move over long distances, are logistically difficult to capture and, as upper-trophic predators, are naturally low in abundance. The scalloped and great hammerhead sharks epitomize such challenges, they are target or bycatch species in a variety of fisheries, and as a result, substantial population declines have occurred in many areas. In the U.S. Atlantic both species are caught in commercial fisheries, however due to their sensitivity to capture (i.e. high at-vessel mortality) reducing quotas or prohibiting landings will not decrease mortality. Thus, alternative methods for their management are urgently needed. In the Bahamas they are protected via the Shark Sanctuary, however little is known about how they use the Bahamas Archipelago. Some research on great hammerheads indicates seasonal residency to islands during the winter months, but Andros Island with its expansive, unaltered habitats offers a year-round, abundant source of food. This research will use a variety of scientific tools, from animal trackers to chemical analysis to examine the movement behavior and ecological role of both species, identifying key habitats, migratory pathways, determining spatio-temporal overlap with fisheries and ultimately generating key data for their improved management and protection.

Conservation concern

Great and scalloped hammerhead sharks (Sphyrna mokarran and Sphyrna lewini) are two large-bodied and highly-mobile shark species that fulfill the role as apex predators throughout their circumtropical range and as such are important for ecosystem stability and functioning. However, due to these species being a target or bycatch species in global fisheries, they have experienced substantial population declines. This has led to both species being listed on the Convention on International Trade in Endangered Species (CITES) Appendix II in 2013 and on the Convention on the Conservation of Migratory Species of Wild Animals (CMS) Appendix II in 2014. Additionally, scalloped hammerhead sharks were the first shark species protected under the U.S. Endangered Species Act. In addition to these listings, hammerheads were identified in 2017 as a priority group that would benefit the most from improved management. There is an urgent need to learn more about their biology, ecology and behavior.

- PROJECT ONE -

habitat, space and resource use of the great hammerhead shark

LOCATION: Andros Island, The Bahamas

RESEARCH QUESTIONS

• How do Great Hammerheads use Andros Island? What habitats do they utilize? Why and when?

• Do Great Hammerheads show residency or site fidelity to Andros Island?

• What role do Great Hammerheads play in marine food webs?

• Where do Great Hammerheads in Andros Island come from / or go to? Are they born in Andros or nearby Cuba? Or are they part of the US population that is from the east coast or Gulf of Mexico?

Funding and Donors

• Saving the Blue, you can support this project by donating via the link found at the bottom of this page, or CLICK HERE

• Fahlo

- PROJECT TWO -

research questions

• Identify the seasonal distribution and relative densities of hammerhead sharks by analyzing data of the US shark bottom longline and US pelagic longline fisheries.

• How do great and scalloped hammerhead sharks move in the US Atlantic and the Gulf of Mexico. Do they travel between the two and are part of one big stock?

• Assess the efficiency of potential time-area closures in reducing fishery-related mortality of great and scalloped hammerhead sharks by combining the output of objectives 1 and 2.

Collaborative Project

Led by Vital Heim and Tristan Guttridge with scientists from NOAA, FSU, DNRSC and BBFS.

Funding and Donors

• Saving the Blue, you can support this project by donating via the link below.

• National Geographic (Explorer’s Grant given to Dr. Tristan L. Guttridge)

• Fahlo