As white sharks gather in Monterey Bay, scientists grab the chance to study them up close

Growing over six meters (20 feet) long and armed with hundreds of serrated, razor-sharp teeth, white sharks are the world's largest predatory fish.

In late summer and fall, up to 250 white sharks congregate in Monterey Bay, off the central Californian coast, to feast on marine mammals -- including elephant seals and sea lions -- that gather here to breed.

From a shark's perspective, "think of Monterey Bay as having one of the best fast food restaurants on the planet," says shark expert and Stanford professor, Barbara Block.

Block also travels to Monterey Bay because the annual marine mammal "buffet" offers her an ideal opportunity to study the sharks up close. She and her team lure the "curious" sharks alongside their small boat, attach electronic tags to their dorsal fins, and then track the sharks as they swim out to the open ocean and dive to depths of 2,000 meters (6,500 feet).

Data on white shark population sizes, life histories and migratory patterns, can be used to inform marine protection policy, says Block, adding that sharks play a vital role in maintaining ecological balance in the ocean. "We need these apex predators to keep our ecosystems healthy."