Surfers in northern California were donning their wetsuits a little more gingerly yesterday after a study of the Pacific’s great white sharks showed just how close to the shore the fearsome predators are lurking.

The sharks cruise the beaches and rocky points to keep close to the colonies of seals and sea lions that make up their main diet. They occasionally even head under the Golden Gate Bridge into San Francisco Bay, according to a ten-year study published in the scientific journal, Proceedings of the Royal Society B.

Scientists combined satellite tagging, acoustic monitoring and genetic tags to study the movements of 179 great white sharks. The tags revealed that the sharks travel a regular route, spending the months between August and December off the beaches of California before swimming to the waters around Hawaii for the spring and summer.

Researchers also discovered that the sharks seem to congregate in an area dubbed the “White Shark Café”, located in the ocean approximately halfway between the Baja Peninsula of California and the Hawaiian Islands.

Scientists said they probably meet there to mate but also just to forage and “hang out” together.

“The thing we’ve learnt about white sharks is that they’re not swimming around aimlessly — they are very selective predators,” Scot Anderson, a marine biologist with the National Park Service, said.

Surfers and swimmers in the waters of northern California have known for years that great whites are in the water — warnings are posted at many beaches — but this is the first scientific proof of how often humans will be sharing the surf with 4,000-pound predators up to 15 feet long.

Shark sightings and beach closures are a regular occurrence. Popular Stinson Beach, north of San Francisco, was closed for five days in August after a surfer spotted a shark, 8 to 10 feet long, about 125 yards offshore.

Attacks by great white sharks are rare, however. There have only been ten documented deaths in 99 attacks in more than 50 years in California — most were surfers or divers in places where elephant seals and sea lions abounded.

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