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An increase in great white sharks in Nova Scotia doesn’t mean divers, swimmers and surfers need to panic about their safety

“Shark! Shark! Shark!” I could hear someone shouting, despite the water in my ears, as I waited in the chilly Nova Scotia water. My heart started racing as I stared through the bars of the shark cage into the emerald abyss.

The plump female great white – nearly four metres long – blasted out of the depths. She grabbed the bait dangling in front of me in her powerful jaws as the scientists onboard the boat above tried to pull it away. She swam right up to the cage, and for a brief second our eyes were mere inches apart. Far from a mindless killer, I saw a fellow being, intelligent and complex.

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A great white shark approaches the cage off Nova Scotia's South shore.

So complex is Carcharodon carcharias – also known as white shark – that scientists are having a hard time answering some of the most basic questions about the animal’s behavior and lifecycle. What do they eat? When and where do they mate and give birth? Where in Canada do they go? How many are even in Canada? (A 2021 report from the Department of Fisheries and Ocean states simply: “The absolute population size of white shark in the Northwest Atlantic is not known.”)

And now, another mystery is unfolding. Over the last five to seven years, many more white sharks have been found off the coast of Nova Scotia. It is a good news story – great whites are a species at risk – but no one can say what’s behind the increase. It could be climate change – or perhaps the sharks have always been here, and people are just becoming more aware of them.

Marine ecologist Neil Hammerschlag has started a long-term monitoring program off Nova Scotia in the hopes of finding some answers – and educating the public. Scientific grants for such work are rare, so he’s turned to eco-tourism, establishing Atlantic Shark Expeditions to help fund his work. Paying guests can go out on the research vessel to look for sharks, participate in citizen science projects and, if they’re brave enough, get close to sharks in an underwater cage, like I did.

The expeditions’ research goals for the sharks include identifying and cataloguing individuals, tracking relative abundance trends (population numbers relative to other organisms) and “evaluating residency and space use patterns.”

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ASE’s Captain Art Gaetan has worked with Canadian sharks for decades and was one of the first to notice the influx of white sharks in the area. He keeps a notebook to track and identify the sharks he sees.

ASE’s Captain Art Gaetan, who works with Dr. Hammerschlag and has been tagging blue sharks in Atlantic Canada for decades, was one of the first people to realize just how many great whites are in Nova Scotia. Even he has a tough time putting a number on the population though.

“At first, no one believed me that there are a lot of white sharks here. But I showed them there are a lot here … a lot,” he told me before my dive in October. “Usually in mid-summer they show up in numbers and stay until the water gets too cold, which is getting later and later, now into November.”

Drawing conclusions about population changes is extremely difficult because there isn’t enough baseline data, says Heather Bowlby, research lead for the Canadian Atlantic Shark Research Laboratory for the DFO.

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Much of what scientists do know about Atlantic white sharks comes from ones tagged off Cape Cod, Mass. That data show mostly juvenile sharks swimming up to Canada seasonally. However, in their first season, Atlantic Shark Expeditions saw 37 great whites – more than they were expecting – none of which were tagged. (Individual sharks were identified though markings, sex and size.) The largest were more than three metres long, and both adults and sub-adults were likely represented.

A tourist looks for sharks from within an underwater cage.
Video courtesy of Atlantic Shark Expeditions

“To me that indicates that what’s happening in Atlantic Canada is something different than just what’s happening with the tagged sharks in Cape Cod. There is something new happening here. There may be a sub-population of white sharks that are not hanging out in Cape Cod, or are there but aren’t being tagged,” Dr. Hammerschlag said.

“So, what’s happening here? I think it’s probably a combination of things. You have a recovering white shark population that was historically overfished, you have ocean warming, which is definitely making the waters more suitable for white sharks for a longer period of time, and the seal populations have rebounded from historical over hunting.”

Boris Worm, a professor at Dalhousie University, attributes the Atlantic increase to shark conservation strategies. “We have more work to do, but this is a significant success story. We should celebrate.”

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Shark tourists get their picture taken before getting in the cage. They travelled from Colorado to see the sharks for their 20th anniversary.

Great whites are one of only three shark species that have global protection, along with basking and whale sharks. According to the International Union for Conservation of Nature, white sharks are vulnerable to extinction, and their worldwide numbers are decreasing.

A recovering Atlantic population is good news for the entire eco-system.

While several other species of sharks are found in the waters around Nova Scotia, most feed on plankton, cephalopods (such as squid) and small fish. As top predators, white sharks affect all the species beneath them including the area’s harbour and grey seals, which have also made a great comeback – a resurgence not everyone is happy about.

Some fishers view the seals as pests and want to start a culling program. For them, news of more white sharks in the area should be welcome. Dr. Hammerschlag’s research in South Africa showed that when it comes to seals, white sharks “not only control numbers, but they also control their behavior through fear. Seals suffer physiological stress, and they generally restrict their foraging to areas where there aren’t white sharks.”

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As apex predators, white sharks affect all the species beneath them including grey seals, which have made a strong comeback– a resurgence not everyone is happy about.

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Eden d'Entremont-MacVicar joins friends for a surf on Nova Scotia's south shore. She accepts that great white sharks are in these waters but isn't going to let that stop her from enjoying surfing.

Of course, many humans also harbour fears of great whites, the largest predatory shark species. But an increase in their numbers doesn’t mean divers, swimmers and surfers need to panic about their safety.

Dr. Hammerschlag and Captain Art say there should be signs at popular swimming and surfing beaches to make sure the public is aware of the sharks. While the risk is not zero, they are quick to point out how small the danger is.

“In all places where there’s white shark tourism there is no evidence whatsoever of increasing risk to bathers,” Dr. Hammerschlag said. “Like in Mossel Bay, South Africa ... there’s been a research boat and eco-tourism boats working there for decades and there was never a white shark bite even though people are wrangling sharks on a bait to cages within yards of a popular swimming beach.

“I think that points out how uninterested sharks are in people and how we are not on the menu.”

The writer travelled with assistance from Atlantic Shark Expeditions. It did not review or approve this article.

A great white shark (Carcharodon carcharias) in Nova Scotia, Canada. The shark teeth cut the rope the bait was attached to, but he cannot eat the large, mostly bone, head of the tuna.

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