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).
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 have provided a wealth of information, we are left wondering where they venture once they have left these areas.
By combining long term photographic identification of individual white sharks from Guadalupe Island, together with long term tracking of these same sharks, the rsearchers at the Marine Conservation Science Institute have put together the most comprehensive study of white sharks in the world.
Since January 2000, PIER and MCSI have deployed 75 pop-up satellite tags at Guadalupe Island 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 1 year and have given us invaluable information on the behavior and movement of white sharks including swimming depths, temperatures encountered, daily patterns, and migratory movements.
Dr. Michael Domeier tags a white shark off of Guadalupe Island
The satellite tagging data has shown that 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. We have found 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.
MCSI 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 our 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, 85 individual white sharks have been identified and tracked at Guadalupe Island. Many of these sharks have been tracked around the island every year since 2001 and 65 of the 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 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, MCSI hopes to learn more about why the sharks are attracted to Guadalupe.
We gratefully acknowledge the support of The George T. Pfleger Foundation and the Offield Family Foundation.