Metro

Here’s what you need to know about avoiding sharks

In 2016, a great white shark ventured within a few yards of the beach in Chatham.
Wayne Davis/Atlantic White Shark Conservancy/Associated Press/File
In 2016, a great white shark ventured within a few yards of the beach in Chatham.

The chances of encountering a great white shark in New England are extremely low. But swimmers should still take precautions.

“They’re the top predators in the ecosystem, and they’re good at what they do,” said Leslie Reynolds, chief ranger at the Cape Cod National Seashore. “We just need to adjust our behavior to stay safe in their environment.”

Here’s what you need to know:

How can I avoid an encounter with a shark?

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National Park Service officials recommend staying close to shore, where your feet can touch the bottom, and never swimming near seals, which are a favorite meal for sharks.

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Be aware of your surroundings and avoid murky or low-visibility water, which makes it difficult for you to see sharks (and for sharks to see you’re a human).

When you’re in the water, don’t wear shiny jewelry (because the reflected light resembles a fish) and keep splashing to a minimum (erratic movements can attract sharks).

Don’t swim at night, and don’t go out into the ocean alone, especially at dawn or dusk. If you want to go swimming, surfing, paddleboarding, or kayaking, take some friends and stay in a group.

The International Shark Attack File website also says beachgoers should exercise caution in areas between sandbars or near steep dropoffs because those places are “favorite hangouts for sharks.” The website also suggests that people avoid wearing bright-colored clothing, refrain from going into the water if they’re bleeding, and keep their pets out of the water.

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People can keep track of sightings by using the Sharktivity app, which is offered by the Atlantic White Shark Conservancy in collaboration with federal, state, and local governments.

How many great white sharks are out there?

“We’re seeing relative increases in the number of white sharks from year to year compared to the historical past,” Greg Skomal of the Massachusetts Division of Marine Fisheries said. “We’ve identified over 350 individual white sharks over the past four years.”

But that’s just a fraction of the total population, he said. The exact number is unknown.

Where are they?

The highest density of great white sharks can be found along the outer Cape, Skomal said. Why? Because that’s where the seals are.

Sharks eat seals, so the bottom line is: Where you find seals, you’ll likely find sharks.

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As the seal population recovers from previously high levels of exploitation and significant declines, “the sharks are changing their distribution in response to this robust food resource,” he said.

A study in a scientific journal last year found that there may be 50,000 seals along the Massachusetts coast. They’re so numerous you can see the ones in the Chatham area from space.

What should you do if you encounter a shark?

It should go without saying — you should never approach or harass a shark. If you see a shark (or a seal, for that matter), get out of the water if you can.

But if a shark attacks you, “a proactive response is advised,” according to the International Shark Attack File website. Hitting it on the nose (ideally with a hard object) is your best bet, and then try to get out of the water.

“If this is not possible, repeated blows to the snout may offer a temporary reprieve, but the result is likely to become increasingly less effective,” the website states. “If a shark actually bites, we suggest clawing at its eyes and gill openings, two sensitive areas. You should not act passively if under attack as sharks respect size and power.”

Emily Sweeney can be reached at esweeney@globe.com. Follow her on Twitter @emilysweeney.