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.
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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.

Preparing to tag hammerhead
using rebreathing apparatus.
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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.
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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.