Project: Movement patterns and habitat use of sharks in the Galapagos Islands: implications for the design of marine reserves
The Galapagos Archipelago is one of the last outposts where large numbers of sharks still linger in the tropical eastern Pacific, but, ironically, have remained largely unstudied. These islands epitomize the conflict between fishers, tourist companies, scientists and conservationists, therefore, studies focusing on sharks and on new and better alternatives to conserve and manage local marine resources are crucial. The latter could foster collaboration and stronger ties between stakeholders. I will address the following questions: How do sharks move in the archipelago? Are there specific physical characteristics that define key habitats for sharks at these islands? How should we design marine reserves for sharks and other marine species?
The specific goals of this project are to
1) understand the movements and migrations of pelagic sharks at the Galapagos Islands,
2) describe and analyze their physical environment,
3) identify ‘hotspots’ or key sites for sharks, and
4) design marine reserves.
Fig. 4. Tracking sharks from a boat
So far, we have tagged more than one hundred sharks (hammerhead, Galapagos and whale sharks) with ultrasonic tags and a number of hammerheads with satellite tags. Preliminary data from records show sharks with one main residency pattern: continuous presence from the end of October to mid-November and few records until January, and then sporadic presence until the end of January (Figure 6). Almost half of the sharks tagged at Wolf Island, 38 km southeast of Darwin, were recorded at Darwin. The first shark tagged at Wolf was detected at Darwin 16 days later. Other sharks tagged at Wolf were also detected at Darwin after two weeks of being tagged, and still others were recorded at Darwin one or two months later. This shows a high degree of connectivity within the far northern archipelago, that is, hammerheads are moving constantly between these islands. Parts of this project have been featured in National Geographic's Shark Superhighway.
One adult hammerhead was
tracked for two
days at Wolf Island. This shark stayed on the east side of Wolf Island
for most of the track, moving at times southwards along the
southeastern shore of the island, and performing constant vertical
movements. We also tagged hammerheads with satellite tags. One shark
traveled more than 800 km (Figure 7) with slow speed overall, showing
some movement in the vicinity of Wolf Island and southwards to the
central archipelago. Another shark moved more than 2000 km at an
average speed four times faster than the first shark (Figure 7). This
hammerhead traversed a large area in a northwesterly direction along an
oceanic ridge where it made some crisscrossing for a couple of weeks
and finally heading towards a seamount by the end of the track.
Fig 5. Satellite tags
This project is part of a regional effort to understand the movements and migratory patterns of sharks and other pelagics of the eastern tropical Pacific known as Migramar, a multi-national network of researchers working at the Galapagos, Cocos, Malpelo, Coiba and Perlas Islands.
Fig. 6. Records of shark detections between October 2007 and January 2008
James Ketchum (co-lead)
Alex Hearn, Ph.D. (co-lead)
Galapagos National Park
Charles Darwin Foundation
Pete Klimley, Ph.D.
Department of Wildlife, Fish, & Conservation Biology, University of California, Davis
Fig. 7. Satellite tracks of hammerhead sharks in the Galapagos Islands
This is a collaborative project between the Biotelemetry Laboratory, the Charles Darwin Foundation, and the Galapagos National Park: The Shark Research & Conservation Program of the Galapagos.
The program has been funded by a number of organizations:
Jastro-Shields Research Fellowship, UC Davis