THE BLOG

We're Swimming With Sharks, and It's Not Really a Problem

06/21/2013 04:47 EDT | Updated 08/21/2013 05:12 EDT

Just last week, there were two shark attacks in the U.S. On June 19, Hawaiian James Kerrigan lost a "good-sized chunk" of his calf to what is thought to have been an attack from a 4.3-meter tiger shark. Two days earlier, a 15-year-old boy was believed to have been bitten by a smaller shark at a Houston, Texas, beach.

Like the hype for a blockbuster movie, the media this spring has been providing us with shocking images and updates of the presence of great white sharks off our shores. In fact, we can track them in real time as they cruise past Cape Cod on their way north toward Nova Scotia. But are Canadians really in danger when they take to the oceans this summer?

The answer to that is a resounding maybe, but not really. Shark attacks in Canada are extremely rare and even the few that have been recorded have been questioned. Far more Canadians have been attacked by sharks while on vacation in other countries than have been in their own waters.

The most recent "attack" in Canadian waters occurred last summer. Kaitlin Dakers, 23, jumped on her surfboard near in Tofino, B.C., last July, lost her balance and fell into the water. When she came out, there was blood everywhere and she was missing part of one of her fingers. She went to a nearby hospital for treatment. Her doctor told her she had been bitten. Dakers was convinced she had been attacked by a salmon shark, a small, fish-eating shark common on Canada's west coast. Consulted by The Globe and Mail, Dr. Kenneth Goldman, a research biologist for the Alaska Department of Fish and Game, disagreed. After examining photos of Dakers' injured hand, he said: "It could be a bite from a smaller animal or an injury from the ocean floor's rocky surface." He added that "other than a couple of scientists working on a boat and getting hit by a tail," salmon sharks had never been implicated in attacks on humans.

Before that, the last encounter was in the summer of 2004 when a father and son were fishing in the Bay of Fundy. The father had hooked a blue shark and when he brought it to the boat, his son reached out and grabbed its snout -- he was trying to "put it in a trance" like he had seen on a TV show -- when it snapped. He required a few stitches, and has a conversation-starter of a scar, but was otherwise unharmed.

A less dubious Canadian attack occurred in December of 2000. Every winter, a few intrepid divers brave the icy waters of the Bay of Fundy -- which have been compared to cold maple syrup -- to harvest sea urchins. One diver, Daniel MacDonald, felt what seemed like a punch in the ribs, followed by another. Then he saw a porbeagle (a very close relative of the salmon shark) grab the mesh bag he used to hold his catch. The shark pulled, dragging him a few feet, then let go.

As with the 2004 bite, it was listed as a provoked attack because it was caused by human interference with natural shark behavior. "It grabbed his bag full of urchins, and when a shark grabs something like that, we consider it provoked," says George Burgess, director of the University of Florida's Shark Research Department, which maintains the International Shark Attack File. "It's like waving a steak in front of a tiger."

And that's about it in recent years. The primary reason that shark attacks almost never occur in Canadian waters is that the water is usually pretty cold and does not attract much human traffic. It's also because the sharks in Canada's waters just aren't the kind that attack humans without provocation. Shark experts believe that sharks attack humans when they mistake them for their prey, and the overwhelming majority of sharks in Canadian waters are fish- or squid-eaters, and are unlikely to be fooled into thinking any human is a really a very large mackerel. And it's also because overfishing and climate change have reduced the number of sharks out there. "Shark populations are down all over the world and Canada is no different," said Warren Joyce, a Canadian Shark Research Laboratory biologist.

But there are a few great whites in Canadian waters. They are rare, generally reported here once every two to five years, but they are present. In August of 1983, an angler landed a 6.1-meter great white in the Gulf of the Saint Lawrence, just off Alberton, PEI.

And everybody knows that great whites are dangerous. Designed to kill and consume large mammals, they can tear off 14 kilograms of flesh in a single bite. They can swim in bursts of 40 km/h literally sending a 120-kilogram seal flying several meters on impact. Unlike other sharks that occur in Canadian waters, great whites often eat big mammals, primarily seals and porpoises. In fact, the great whites that have been tracked by Dalhousie University are believed to be headed to Nova Scotia's Sable Island to feed on some of the 300,000 or so gray seals that live there.

But while they are huge and powerful and they can sometimes mistake humans for their preferred prey, their threat to humans has been overblown, especially here. Since 1876, great whites have been responsible for 69 human fatalities, and not a single one in Canada. At least not directly.

Four attacks have been attributed to great whites in Canadian waters -- and all of them have been against boats.

The most recent occurred off the Cape Breton community of Fourchu in July 1953. Two lobster fishermen, John D. Burns and John MacLeod, were shocked when their dory was rammed repeatedly from below. The attacker -- indentified by a tooth left embedded in the boat as a great white -- eventually burst a hole in the hull, sinking the boat. Later dubbed the "Fourchu Rammer," the shark became famous and a drawing of the event even appears in Jaws. The two men were dumped into the Atlantic, but the shark did not attack them. Burns drowned, washing ashore the next day without any bite marks.

There are other big sharks in Canadian waters, but they are considered less likely to harm humans.

Shortfin mako sharks certainly look fearsome, and can be aggressive, but are fish eaters and have only been linked to attacks involving fish, such as fighting a spear fisherman for an already wounded fish or when tangled in a net, and none have occurred in Canadian waters.

Basking sharks can be the size of a bus, but they are filter-feeders, eating plankton, invertebrates and tiny fish. It has been postulated that a basking shark could accidentally swallow a human, but it's unlikely to the point of ridiculous.

Similarly, slow-moving sixgill sharks can be up to five meters long, but just aren't very aggressive. "You have to respect the sixgill's size, but they are tolerant," said Dr. Chris Harvey-Clark, a marine biologist at the University of British Columbia and Canada's foremost shark authority. "I've never heard of an attack, and I've seen people pull their tails and try to ride them."

Greenland sharks are even more sluggish and, because of a common parasite that attacks their eyes, virtually always blind. And they generally enjoy water temperatures that would be intolerable for humans. Back in 1859, part of a human leg is said to have been found in the stomach of a Greenland shark near Pond Inlet on Baffin Island, but, if it was true, it was almost certainly a case of scavenging, not predation.

So while it is true that if you dare to go into the Atlantic this summer, you will be sharing it with sharks, even a few great whites. But be aware that they really don't want to have anything to do with you.

I suppose that if you made your way to Sable Island -- which, unless you're a scientist, is essentially illegal -- and jumped into the cold, deep water while wearing a seal costume, then swam out a few hundred meters, you could be in danger of being attacked by a great white shark in Canadian waters. Otherwise, you're pretty safe.