Project: Tracking migratory pathways of hammerhead sharks for the creation of marine reserves

Introduction:

A precipitous decline in the shark population of sharks in the Gulf of California has led U.S. and Mexican scientists to propose the establishment of marine reserves , where fishing would be restricted in the future. It is imperative to create these reserves based on sound scientific knowledge of the life history of the resident species. Studies must be carried out the answer the following questions. Where should these reserves be located? How large should they be? How many separate reserves are needed to protect species that migrate over great distances?

Tagging hammerhead shark while free diving.

Objective:

We want to compare tracks of the movements of hammerhead sharks to the regional topography to ascertain whether hammerheads migrate between subtropical and tropical zones by moving from island to seamount as "stepping stones". If we find that sharks move from seamount to seamount (or island to island), we will recommend that resource managers prohibit fishing in small areas around seamounts and islands, conservation "donuts."

Progress:

We will be placing three types of electronic tags on hammerhead sharks to record the degree of their tenure at sites and extent of their migratory movements in the Eastern Pacific. During fall 2002, long-term ultrasonic beacons were attached to adult hammerhead sharks by diving into the schools present at the Espiritu Santo Seamount and the tenure of their residence at the seamount is currently being recorded with automated tag-detecting monitors moored at the site.

We are affixing pop-up archival tags (PATs) to adults that will release after a period of a year and provide a daily record of the shark's geographic positions. We are presently working within the Gulf of California where populations seem to have been hit the hardest and hammerheads have become scarcer. Next we will focus on the Revillagigedos, Cocos and the Golapagos islands where members of the species are more abundant. We will also be placing archival tags on juvenile hammerhead sharks during the winter season. These electronic tags also record geographical positions, but must be retrieved and the files contained within them downloaded after capture of the tagged fish.

Personnel:

Salvador Jorgensen (lead)

Pete Klimley, Ph.D.

Department of Wildlife, Fish, & Conservation Biology, University of California, Davis

School of sharks swimming over Espiritu Santo Seamount.

 

Nallely Aguilar-Castro

Felipe Galvan-Magana

Centro Interdisciplinario de Ciencias Marinas, La Paz, Baja California Sur, Mexico

Funding Agencies:

Committee for Research and Exploration, National Geographic Society: UC Mexus, University of California.