If you fear shark attacks, you're not alone. Even though accidents involving toasters kill more people each year, there's something unnerving about the thought of being in the water with a predator.

On Friday, November 24, a man spear fishing in Monterey Bay was attacked by a shark -- probably a white shark. He's expected to be OK. Each time a reported shark attack appears in the news, though, it can stoke panic.

Take some comfort, then, in the knowledge that your risk of a shark attack is low, almost unbelievably low.

What's more, the risk of shark attack has been in long-term decline. (We still advise due caution when in the water.)

According to a study out of Stanford's Hopkins Marine Station, shark attack risk on the California coast has dropped by more than 91 percent since 1950.

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The study, published in Frontiers in Ecology and the Environment, weighted the number of reported attacks in the last 60 years in the state against the number of people using the ocean for swimming, diving, surfing and other sports. While the number of statewide attacks has remained relatively steady (about one per year on average in the '50s to one-to-two per year now) the number of people in the ocean has ballooned.

"So right now your chances to have a shark interaction is much lower than it was in the '50s," says Francesco Ferretti, a shark researcher who studies the human impact on ocean health.

The best hypothesis for explaining this pattern, Ferretti says, is the amazing recovery of pinnipeds -- seals, sea lions, elephant seals -- in California. These animals were basically hunted to extinction at the beginning of the last century, exploited for fur and fat. Their recovery began in the mid-20th century. "Now they are skyrocketing in many places around California," Ferretti says.

Ferretti and co-researchers suspect that since seals tend to live in large groups in predictable areas -- such as the Farallon Islands or Año Nuevo, north of Monterey Bay, white sharks know where to go to get a meal. It's possible they're not spending as much time roaming up and down the coastline as they once did.

As predators, sharks play key roles in ocean ecosystems.

"The sharks are kind of the police of the ocean," says Ferretti. "They keep in balance things that [would] get out of control."

Francesco Ferretti doing field research on shark abundance in Palau.

The presence of top predators helps ensure stability and balance in fish stocks.

For example, it's suspected that on the East Coast, killing sharks contributed to the collapse of a scallop fishery in North Carolina, because sharks kept the rays -- which eat scallops -- in check.

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Ferretti's data is practical too. He says learning about the ecology and movement of sharks can do much more to decrease the risk of shark attack than culling sharks.

Risk of shark attacks is highest, he says, in the months of October and November in Northern California. For surfers, for example, risk can be reduced 25-fold by surfing in March instead, and by more than 1,600-fold by surfing in Southern California, between Los Angeles and San Diego.

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