As climate change disrupts ocean temperatures, a significant trend is emerging: more sharks are heading north into Canadian waters. And experts say Canadians may need to get used to these new marine neighbours as sightings increase along the coast.
This northward shift includes great white sharks, tiger sharks and blacktip sharks, which are now appearing closer to shore along the eastern seaboard in Canada.
As the number of sharks increases, so does the frequency of human-shark interactions.
“A lot of these sharks are fairly close to the beach where the people are and that’s something I would encourage people to be aware of,” warned Dr. Stephen Kajiura, a professor in the department of biological sciences at Florida Atlantic University.
“They’re cruising in the water and you’re seeing more and more sharks coming farther and farther north than ever before.”
Once a rare sight in frigid northern waters, sharks are becoming increasingly common. Growing evidence suggests a rise in great white shark populations, specifically along Canada’s East Coast.
Aside from more frequent sightings, there have been reports in Nova Scotia of two shark attacks in recent years, one of which injured a swimmer and another that killed a dog.
Shark sightings are becoming so common that Neil Hammerschlag, the executive director of the Shark Research Foundation and president of Atlantic Shark Expeditions, said Nova Scotia may soon start putting warning signs on beaches.
Although there are more sharks in Canadian waters, he stressed that this is a sign of a healthy ecosystem, as a large prey population is needed to support sharks.
“We know they’ve been overfished, historically, where the numbers plummeted. So to start seeing more numbers is a good sign,” he said.
With this influx of sharks in Canadian waters, Kajiura and Hammerschlag both warn that these encounters may become a new normal for Canadians.
“You’re going to start to see the big boy off Canadian maritime provinces. And so that’s something else that Canadians need to be aware of — the world is changing,” Kajiura said. “The climate is changing, the oceans are changing. And as a result of that, we have to adapt as well. We have to be more vigilant.”
Great white sharks primarily eat fish, marine mammals like seals and sea lions, other sharks and occasionally sea birds.
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Climate change and sharks
Sharks are migrating into northern latitudes earlier and expanding their movements farther north due to ocean warming, according to the NOAA Fisheries, a United States federal agency.
A 2022 study published in Global Change Biology found that tiger sharks’ seasonal distribution has expanded in the northwest Atlantic Ocean over the last several decades. This northward expansion was driven by climate change, specifically the overall warming of the coast along the northeastern U.S. coast, researchers found.
Hammerschlag, who studies tiger sharks, said these predators prefer tropical and subtropical ocean temperatures. But he is starting to see tiger sharks expand their migration range farther north from Long Island N.Y., to Cape Cod, Mass.
“There have been instances of tiger sharks encountered in Nova Scotia and waters in Canada,” he said, adding that although it’s not common, “it might be more common in the future as the temperatures here continue to rise.”
Tiger sharks prefer warm, tropical and subtropical waters, typically in coastal areas, but are starting to migrate more north as the ocean warms.
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As the waters in the north become more hospitable, more sharks, like great whites, are making their way into Canada, Kajiura said.
“We can attribute that to climate change. The water in the ocean is getting warmer and warmer, and the sharks can extend their range farther and farther north because the water’s sufficiently warm for them,” he explained.
“We’re seeing this shift in the distribution of sharks — there may not be as many down south, like Florida, but there’s more farther north. We’re getting sharks off Long Island, New York, now.”
Shark attacks have risen recently in New York state.
For example, in August 2023 a woman was seriously injured after a shark bit through her thigh while she was swimming at a New York City beach, officials said, an unusually severe attack that appeared to be without precedent.
“They were never there a decade ago,” Kajiura said. “And so because of this change in water temperature, these sharks are going farther north … and it started to become more and more of an issue in New York, where we had a record number of shark bites right here. And that is something climate change has helped trigger.”
Shark movement northward isn’t solely driven by climate change. A confluence of factors, including increased baitfish populations, successful conservation efforts and more people enjoying the water, contribute to more shark sightings and interactions.
Shark populations, especially in the Atlantic Ocean, have been heavily fished for their meat and fins, Hammerschlag said. This has led to dramatic declines in their numbers.
Blue sharks are commonly found off the Atlantic coast, particularly around Nova Scotia and Newfoundland, as they prefer temperate and cool waters.
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Thankfully, he said, there have been significant efforts in the last decade to protect sharks and prevent further decline.
“There is some evidence that certain shark populations are increasing, as a result of that protection, which is an excellent sign.”
The rebound of fish stocks in the ocean has led to an increase in the number of seals and other prey, resulting in a rise in shark populations.
“And as a result of that you’re getting more and more of these large predators coming back,” Kajiura said.
Lastly, Hammerschlag noted that with more people in the ocean than ever before, the likelihood of encounters with sharks has increased.
“I would say because of ocean warming and the atmosphere warming, it’s hotter outside. So people are going to the ocean and spending more time there; it increases your chance of an encounter,” he said.
“If you look at the stats … when there seem to be more shark bites during holidays and weekends, sharks aren’t thinking, ‘Oh my goodness, it’s a Saturday or it’s July 4 weekend, a good time to go bite someone.’ It’s just because there are so many more people in the water. So shark bites reflect more about human behaviour than they do about shark behaviour.”
Sharks don’t like the taste of humans
The yearly average of unprovoked shark bites on humans globally is 70, resulting in about five deaths, according to the International Shark Attack File.
These worldwide numbers are small given the millions of humans that enter the water. You have a better chance of dying from a bee sting, a dog or snake bite, or lightning than from a shark bite, the website stated.
“The point to remember is that they’re very rare and that’s why they make the news,” Kajiura said. “It looks like there’s been this large increase in shark bites, but in reality, we’re about at the same level that we have been at this time of year, historically.”
Sharks have a diverse palate. Many species rely on a steady supply of fish. Powerful predators like the great white and tiger shark hunt marine mammals such as sea lions and dolphins. Bottom-dwelling sharks prefer crustaceans, scavenging for crabs and lobsters.
One food they don’t like to eat is humans.
“Sharks are interested in feeding on the little prey items. And humans, we’re not part of the menu. They’re certainly not interested in us. There’s no drive to suddenly start eating people,” Kajiura said. “And so when people are bitten, it’s usually because the shark mistook it for something else.”
While humans aren’t on the regular menu for sharks, unprovoked attacks can still occur. Sometimes, a shark might mistake a human for its usual prey, like a seal or a fish.
“A lot of the bites on people are basically the result of mistaken identity,” Kajiura said. “So, a person is swimming around in the water, and it may be that they’re wearing jewelry that could catch the light and looks like a little fish. And the shark will come up and investigate that. And they don’t have hands, so they investigate with their mouths. As a result, people get bitten.”
Hammerschlag and Kajiura recommend a few safety tips for swimmers heading into the ocean to reduce the risk of shark encounters.
Ditch the bling
Whether it’s a watch, necklace or pair of earrings, Kajiura said people should avoid wearing jewelry in the water near sharks because it can sparkle and mimic the appearance of fish scales, potentially attracting the predators who mistake it for prey.
“The shark might be drawn to that and bite your hand or your foot,” he warned.
Avoid areas where people are fishing
If someone is fishing along the beach or off a dock, Hammerschlag advised staying clear of that area as it may attract sharks.
“Sharks are opportunistic and a fish that is being hooked on the line is struggling, it’s bleeding. So the sharks can sense vibrations in the water, they can sense that struggling fish, they can also smell the blood,” he explained. “That’s very attractive to a shark, if a fish is struggling and swirling around, that’s ringing a dinner bell to a shark and you might not want to be standing right there.”
Avoid swimming in the early morning, late evening
It’s best to avoid swimming under low light conditions because if it’s dark it’s more difficult for a shark to distinguish a foot from a fish, Kajiura said.
“If you’re swimming at dusk or dawn when the visibility isn’t very good or the water’s really murky, it makes it more difficult for the shark to clearly distinguish that you’re a person and not a little prey item,” he said.
Go to a beach with lifeguards
Kajiura recommends swimming at a beach that has lifeguards, that way they can inform people if there have been any recent shark sightings, and “it’s also another set of eyes watching the water for you.”
“They can also whistle and let you know to get out. In addition, if you do happen to get bitten or you’ve got immediate medical help right there to assist,” he added.
Whether or not you decide to pack your beach clothes and take a dip in the ocean this summer, Kajiura reminds people that encountering a shark is still very rare. Sharks are always in the water, but they don’t have a taste for humans.
“So when you’re down at the beach having a good time splashing around, you have probably been within range of a shark without even knowing it,” he said. “And so I would encourage people to continue to go to the beach and then continue to have a good time with a few things to look out for.”
— with files from Global News’ Katherine Ward and Kathryn Mannie, The Canadian Press and The Associated Press
