Like the swirls on a human fingerprint, the shape and notches of each white shark’s dorsal fin are unique, enabling scientists to catalog and track sharks across the oceans, according to great white shark researchers at the Monterey Bay Aquarium, which since 1987 has been photographing dorsal fins – first in waters off the Farallon Islands, and later at Año Nuevo Island and Tomales Point.
This photo database helps scientists understand the migration route of white sharks and whether they return to the same waters on a regular basis. Fin IDs also help them estimate the number of white sharks at these locations, and monitor the survival of individual animals.
In 2013, of the 80 individual adult white sharks photographed by researchers from the Aquarium and other institutions, nearly 65 percent had been seen in previous years.
Several have been coming back to the same waters for more than 20 years. One, a 16-foot male known as “Tom Johnson,” has been sighted for the last 26 years - the longest tracking period for any white shark on earth.
Read more about how researchers use the great white shark dorsal fin as clues to identify and protect them on the Monterey Bay Aquarium website here.