ABSTRACT
Photo-identi¢cation (photo-ID) techniques have been used to monitor and track northeastern Paci¢c White Sharks (Carcharodon carcharias) at a seasonal adult aggregation site at Guadalupe Island, Mexico. Between 2001 and 2009, 142 sharks have been photographed, 113 of which have been entered into a catalogue that requires both the left and right sides to be photographed. This catalog consists of 67 males (59%) and 46 females (41%). The photo-ID data demonstrated White Sharks to be present at Guadalupe Island between late July and December, although effort past December was minimal. Sharks exhibited seasonal site ¢delity, with 83% of the sharks in the catalog sighted in at least 2 yrs. and 28% sighted in at least 5 yrs. of the study. Males were found to return to the island earlier than females, with the sex ratio reaching parity in November. Males were more likely to be sighted in consecutive years, whereas females were more likely to exhibit a nonconsecutive year visitation pattern. However, only a small percentage of sexually mature females exhibited a consistent every-other-year pattern, which has been proposed to be associated with an 18-month gestation cycle. The continuation of this photo-ID program will provide important data on life history, migratory patterns, and abundance, which will aid in the management and conservation of this vulnerable species.
