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BACKGROUND
Although the white shark inhabits all of the oceans, we need to add additional information to existing data about basic aspects of its biology. In Mexico, available information is mostly anecdotal in nature or based on dead specimens, providing little insight into the biology of living sharks. Recently, Guadalupe Island was considered an important great white shark aggregation site in the eastern Pacific, representing a key population monitoring site for this species in our country. We have initiated a collaborative research program between the University of California-Davis, and Centro Interdisciplinario de Ciencias Marinas (CICIMAR) since 2004, focusing on the behavior, feeding, and genetics of white sharks at Guadalupe Island.
TELEMETRY
Acoustic telemetry had been used in Guadalupe Island to successfully track white sharks. In previous years we used an ultrasonic receiver with a directional hydrophone to detect sharks tagged with acoustic transmitters with depth and temperature sensors. This technology was designed for manual tracking of aquatic animals from small boats. So far, we have tracked multiple white sharks and have learned much about their behavioral patterns while swimming in the waters surrounding the island (see results).
Currently we are using underwater receivers known as VR2W and coded tags (Vemco ltd.). This technology is ideal for multi-tracking operations in large oceanic systems. The VR2W were installed by divers at 30 m depths with special moorings. The monitors will be underwater for 8 months and the information recorded is going to be used to identify seasonal movements, preferred habitats, and behavioral patterns of the white sharks at the island.
Also we have collected tissue samples for two different analyses:
STABLE ISOTOPES
Isotope analysis is the identification of isotopic signature, the distribution of certain stable isotopes and chemical elements within chemical compounds. This can be applied to a food web to make it possible to draw direct inferences regarding diet, trophic level, and subsistence.
GENETICS
Estimates of population differentiation on the basis of the control-region sequences have shown that the white sharks from Australia and New Zealand coastal waters are not significantly different, but individuals from these populations are distinct from South Africa sharks. In Guadalupe island we have taken several biopsies and the samples are being analyzed in order to know the relation of this population with others from the world
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Guadalupe Island is inhabited by a large population of great white sharks (Carcharodon carcharias). Ultrasonic telemetry provided a description of the movement patterns and swimming depths of juveniles and adults white sharks ranging from 1.8 meters to 5 meters total length. The following was observed:
Juvenile
Adult
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