Michelle Terrell is a mother of five who moved from the East Coast to Mill Valley six years ago. Her kids wanted to learn how to surf when they got here, so she enrolled them in a surf camp.
“And I would say half-joking when they got back from surf camp, ‘I’m glad a shark didn’t eat you today,’ ” says Terrell.
And now she actually wants to know:
Do swimmers and surfers really have to be afraid of sharks when going out into the bay?
You are not much at risk of a shark attack in the waters off California. You’re much more likely to win an Oscar, be born with 11 toes or get hit by a car than be bitten by a shark.
That said, the Pacific Ocean is home to loads of sharks. Including the shark we most fear — the great white shark.
Juvenile white sharks can be found mostly in Southern California and are far less dangerous than their fully grown counterparts.
“They are almost two different species,” says Salvador Jorgensen, a senior research scientist at Monterey Bay Aquarium.
As the white sharks get bigger, they head north to where they can find larger, fat-packed prey — seals. There’s a high concentration of elephant seals and other pinnipeds in a stretch of coastline between Northern and Central California. It starts in Bodega Bay, extends out to the Farallon Islands and ends around Monterey Bay.
“This is the area with the highest concentration of white sharks in the northeastern Pacific probably,” Jorgensen says.
This area is sometimes called the Red Triangle because, if you look on a map, it makes a triangle.
“Supposedly it refers to all the blood in the water,” says Jorgensen. He means seal blood.
But white sharks can often be found outside the red triangle. You can actually spot them all along the coast.
“Mendocino is also a major hot spot for white sharks,” says Francesco Ferretti, a marine ecologist at Hopkins Marine Station of Stanford University.
But What Are My Chances, Really?
Jorgensen and Ferretti have researched the actual risk of shark attack in California.
They found that surfers have the most frequent shark encounters by raw numbers, followed by abalone divers, scuba divers and finally swimmers. However, if you control for the number of people doing these activities, abalone divers are most at risk.
“Abalone divers are most at risk with a 1 in 1.44 million chance of being attacked. Surfers have a 1 in 17 million chance of a shark attack. People going to the beach, just swimming, have a one in 700 million chance to have a shark bite,” says Ferretti.
Humans are not the preferred prey of sharks. Our stringy bodies are far less appetizing than a fat-packed seal, the chubby dumpling of the ocean. This might explain why sharks occasionally bite surfers, because from below, they kind of look like seals.
“Sharks explore potential prey by biting it,” Ferretti says. “They bite otters as well. As they grow and learn about potential food sources, sometimes they make a mistake."
To reduce your risk, you could surf outside the hot spots or avoid the water at certain times of year.
To help remember riskier months, some use the term "Sharktober."
“That's when white sharks are around the Bay Area,” says Jorgensen. “October, November is pretty much the peak, then that tapers off in January when the sharks are moving offshore.”
When they aren’t in the Red Triangle, our great white sharks swim in the waters around Hawaii, or in an area halfway between here and Hawaii called the White Shark Cafe.
“The White Shark Cafe is a really desolate part of the ocean. There’s not a lot going on when you look at it from space,” says Jorgensen.“In fact it was called the Desert of the Pacific by many oceanographers. I always think about it a little bit like Burning Man. We have got these Bay Area sharks out here in Central California and once a year they head off into the desert. God knows what they’re doing out there. But we’re trying to find out.”
Between 1950 and 2013, there was an average of 1.37 white shark attacks per year, with an increasing trend from .9 attacks per year in the 1950s to 1.5 attacks per year in the last decade of the study. In that time there were 13 recorded shark fatalities in California and only one near the San Francisco Bay.
While the number of shark encounters in California has gone up, the risk has dropped about 90 percent between 1950 and 2013.
“We have an increasing population all around the world. If you put more people in the water you would expect more encounters with sharks,” says Jorgensen. “But what we've seen in California is that encounters and injuries inflicted by sharks have increased a little bit over the past 50 years but the number of people in the water has increased immensely, so that ratio has decreased.”
The reduced risk could be a sign of a declining shark population.
“There are on average about 10 human fatalities per year worldwide. If you compare that to the number of sharks that have died at humans hands, that is more on the order of 50 to 100 million sharks per year,” says Jorgensen. “The equation is it's very one-sided there.”
According to Ferretti, most sharks are killed through industrial fishing and the fin trade.
“They are dying on the high seas, and many are targeted for their fins,” Ferretti says, adding that sometimes a shark’s death is unintentional, “Blue sharks, silky sharks, hammerheads and thresher sharks, those are the species that can be caught as bycatch in large quantities.”
At Hopkins Marine Station, Ferretti works in a lab where researchers are developing innovative tools to combat illegal fishing in the high seas. They’re looking into creating tags that would detect illegal fishing, and drones that could patrol the waters.
The lab also studies movement patterns and the distribution of sharks throughout the ocean. They’ve been researching what shark populations looked like before industrial fishing killed millions. Lately they’ve also been looking at the importance of sharks in protected and thriving ecosystems.
“As apex predators, they help stabilize entire ecosystems. When sharks are thinned out at the top, animals further down the food chain can become overhunted,” says Ferretti. “For example, a scallop fishery in North Carolina was decimated due to a declining shark population.”