Great hammerhead sharks off Andros Island defy expectations by staying year-round in Bahamian waters, revealing the sanctuary as a vital, permanent stronghold for this endangered predator.
Great hammerhead sharks (Sphyrna mokarran) off Andros Island in The Bahamas exhibit year-round residency and strong site fidelity, primarily feeding on barracuda and small sharks, according to a new study [1]. This challenges previous ideas that the Bahamian shark sanctuary serves only as a seasonal refuge for this critically endangered apex predator.
Understanding the movement and ecological role of great hammerheads is vital for their conservation, given their global population decline of over 80% in recent decades and their key role in marine ecosystem stability [2,3]. The Bahamas shark sanctuary is considered a crucial area for regional population recovery efforts.
The study was conducted by Tristan L. Guttridge and colleagues from Saving the Blue (Florida), Florida International University, and NOAA Fisheries, and was published in Frontiers in Marine Science in March 2025. Researchers used fisheries-independent drumline captures, satellite telemetry, and stable isotope analysis to investigate the residency, space use, and diet of great hammerheads around Andros Island, the largest island in The Bahamas.
Between March 2020 and June 2024, sharks were captured using drumlines along the reef drop-off and flats of Eastern Andros. Satellite tags recorded their movements, while muscle biopsies enabled stable isotope analysis to identify prey species. The study also incorporated opportunistic sightings to supplement data [1].
Results revealed that many great hammerheads remain in Bahamian waters throughout the year, showing strong site fidelity to habitats along Andros’ reef drop-off and flats. Isotope analyses indicated a diet dominated by barracuda and small-bodied elasmobranchs, linking pelagic and coastal food webs. This suggests that the Bahamian shark sanctuary is more than a seasonal stopover—it is a critical habitat supporting resident populations of this highly mobile species.
The study is not without limitations, including potential sampling bias due to the focus on Eastern Andros and the relatively small sample size of tagged individuals. The sensitivity of great hammerheads to capture stress also constrained tagging efforts.
These findings have important implications for conservation management. Recognizing Andros and the Bahamian shark sanctuary as year-round habitats emphasizes the need to maintain and enforce protections in these waters to support population recovery. [3] It also underscores the ecological importance of great hammerheads in connecting coastal and pelagic ecosystems through their feeding habits.
Our understanding of great hammerhead and predator ecology is improving. By demonstrating year-round residency and specific habitat use in The Bahamas, the study highlights the sanctuary’s critical role beyond a seasonal refuge [3,4]. Continued research and conservation efforts are essential to safeguard this apex predator and the marine ecosystems it helps sustain.
Why it matters.
Where, when, and how marine predators use the marine ecosystem is central to effective conservation, ecotourism, and fisheries management. In a rapidly changing world, understanding how sharks move and what they do will also help us to understand how environmental conditions may affect their lives.
References
[1] Guttridge TL, Heim V, Dedman S, Guttridge AE, Bain SA, Keller BA, Matich P. (2025). Stay or go? Space and resource use of the great hammerhead (Sphyrna mokarran) off Andros Island, The Bahamas. Frontiers in Marine Science, 12:1544482.
[2] Rigby CL, et al. (2019). Sphyrna mokarran. The IUCN Red List of Threatened Species 2019.
[3] Sherley RB, et al. (2020). Global population reduction of great hammerhead sharks exceeds 80%. Conservation Biology.
[4] Haas AF, et al. (2017). The Bahamas shark sanctuary: a model for marine conservation. Marine Policy Journal.
Image – Underwater View Of Great Hammerhead Shark Swimming, Low Angle View, Alice Town, Bimini, Bahamas is a piece of digital artwork by Ken Kiefer 2 uploaded on March 2nd, 2021.
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