BioEd Online

The longest ever attempt to keep a great white shark in captivity has come to an end. After six months, officials at Monterey Bay Aquarium in California were forced to release the female shark as she lived up to her reputation and began killing her tank-mates.

Aquarium staff returned the shark to the Pacific Ocean near Point Pinos, California, on 31 March, marking an end to her 198-day stay. She was accidentally caught in a fisherman's net off southern California in September last year.

But researchers at the aquarium aren't yet finished with the shark. She is equipped with a tag containing instruments to measure her whereabouts, depth of dives and preferred water temperature. After 30 days the tag will release itself and float to the surface, where it will transmit its findings to a satellite.

Besides allowing marine scientists a close and personal view of a great white (Carcharodon carcharias), the 70-kilogram shark has boosted the aquarium's fortunes. Public attendance at the tourist attraction surged by almost one-third after her arrival.

But her aggressive behaviour ultimately led to the decision to remove her from the tank she shared with several other sharks and fish. "There was a clear sense she was hunting other animals," says aquarium spokesman Ken Peterson.

Not least among these were two soupfin sharks who died as a result of her attacks, although aquarium officials maintain that other species with which she was housed remained safe. Experts at California's Pelagic Shark Research Foundation had previously argued that aggression towards other sharks was a sign that she did not have enough room to roam.

The great white's nose was damaged by rubbing the tank walls during her captivity, perhaps another sign of stress. The aquarium's veterinarian found no infection at the site of the wound, however: "Her overall health was excellent, as are her prospects for survival in the wild."

The aquarium remains keen to study great whites, and has pledged to try to obtain another one for further study. "We hope to bring another to Monterey so we can continue to change public attitudes about this feared and much-maligned ocean predator," the website says.