White Sharks of Guadalupe
 Very few animals generate the mixture of fascination and terror as does the great white shark. Unfortunately, the terror-associated, anti-shark sentiment has led to the unnecessary slaughter of many animals. Fortunately, white sharks are now protected in California waters and are listed as a threatened species in the Pacific (appendix II of Convention on International Trade in Endangered Species of Flora and Fauna, CITES). PIER’s research goal is to increase the knowledge and understanding of these fascinating animals.
Studies of these powerful sharks have been limited by the difficulty of gaining access to them. They are difficult to capture or handle, and working with free-swimming animals has its obvious complications. Most information is available from dead specimens or from shore-based research stations. While observations of animals from shore has provided a wealth of information, we are left wondering where they venture once they have left these areas. The pop-up satellite tag provides the perfect opportunity to address their large-scale movements.
Beginning in the winter of 2000, PIER initiated a long-term study on the movements of great white sharks off the coasts of Southern California and Mexico. Research on adult sharks has been focused at Guadalupe Island, off of Baja California, Mexico. For the last several years, large numbers of sharks have been observed at Guadalupe.
A white shark is tagged off of Guadalupe Island
Since January 2000, PIER has deployed 58 pop-up satellite tags at this site on sharks ranging in size from 8 to 18 feet long. Tags are inserted into the backs of the sharks (as close to the dorsal fin as possible) as they are lured close to the boat with large tuna carcasses. The tags have remained on the sharks for anywhere from 2 weeks to 9 months and have given us invaluable information on the behavior and movement of white sharks including swimming depths, temperatures encountered, daily patterns, and migratory movements.
PIER has found that the tagged sharks remain at Guadalupe Island for a portion of the tagging period, but they leave the island for as much as half the year and travel very long distances. Tagging data has shown that they are traveling towards the middle of the Pacific Ocean, towards offshore seamounts. This suggests that even away from shore, animals may be drawn to topographical relief features in the ocean. Such features are frequently gathering places for a wide variety of marine inhabitants.
PIER has also been studying the sharks at Guadalupe Island through a rapidly expanding photo-identification project. Individuals have been identified using photos and video taken by PIER’s research team as well as by photographers and divers on cage-diving expeditions at the island. Using physical features such as: pigmentation patterns, the sex of the animal, and any scars and mutilations, 50 individual white sharks have been identified and tracked at Guadalupe Island. Many of these sharks have been tracked around the island since 2001 and 35 of the 50 identified sharks have been photographed at the island over multiple years.
It is clear that great white sharks are drawn to the area around Guadalupe Island. The challenge remains to determine why they have selected this spot. Perhaps they are taking advantage of the local seal colonies on the steep rocky shores. Guadalupe is also known for as a prime fishing spot for recreational anglers. The large tuna and yellowtail that are found here may also attract one of the oceans largest predators. Through additional research, PIER hopes to learn more about why the sharks are attracted to Guadalupe.
PIER gratefully acknowledges the support of The George T. Pfleger Foundation
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