Project: Movement patterns and habitat use of sharks in the Galapagos Islands: implications for the design of marine reserves

 


Fig. 1. Tagging a whale shark while free diving.
Fig. 1. Tagging a whale shark while free diving.

Introduction:

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?

Fig. 2. Underwater receiver
Fig. 2. Underwater receiver

Objective:

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, 

Fig. 3. Location of listening stations at the Galapagos
Islands
Fig. 3. Location of listening stations at the Galapagos Islands

3) identify ‘hotspots’ or key sites for sharks, and 

4) design marine reserves.

Methods:

Since 2006, sharks have been tagged with acoustic transmitters and satellite tags during fieldwork at the Galapagos Islands, mostly by free diving using pole spears (Figure 1). Such transmitters communicate with underwater receivers (listening stations; Figure 2) that have been placed at key sites throughout the archipelago (Figure 3). I will retrieve and analyze the records of individual transmitters at the listening stations to learn about the sharks' daily movements into and out of the key sites. I will also follow six individual sharks from a boat (Figure 4). Each shark fitted with transmitters that send information on how deep the shark goes and the temperature of its surrounding water. Sharks fitted with satellite tags (Figure 5) will relay daily geographical coordinates, diving profiles, and water temperature, which will be displayed on a web site with weekly updates (www.migramar.com). All of this work will be carried out with the participation of Ecuadorian scientists from the Galapagos National Park (GNP) and the Charles Darwin Foundation (CDF).

Fig. 4. Tracking sharks from a boat
Fig. 4. Tracking sharks from a boat

Progress:

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
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 and January
Fig. 6. Records of shark detections between October 2007 and January 2008

Personnel:

James Ketchum (co-lead)

Alex Hearn, Ph.D. (co-lead)

Eduardo Espinoza 
Galapagos National Park

Cesar Penaherrera
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
Fig. 7. Satellite tracks of hammerhead sharks in the Galapagos Islands

Funding Agencies:

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:

Conservation International

World Wildlife Fund

National Geographic Society

Iemanya Oceanica

Hemispheric Institute on the Americas, UC Davis

Galapagos Conservation Trust

Swiss Friends of Galapagos

Lindblad Expeditions

Jastro-Shields Research Fellowship, UC Davis

University of California Institute for Mexico and the United States Fellowship (for Doctoral studies at UC Davis)

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