Having blogged about sharks in Canada going on 6 years now, I’ve noticed a few rumours that consistently pop up. The first is that a great white shark was caught in Ucluelet BC in 2005. That didn’t happen, and the second, that there are bull sharks in Lake Ontario or the Ottawa River, is nothing more than a case of bull sh(ark!). Bad pun, I know…
Yet there is actually some truth to the third rumour, that a great white shark could be in the St. Lawrence vicinity. Well, let’s modify that a little; the second largest great white shark ever measured was caught in the Gulf of St. Lawrence back in 1983, off Prince Edward Island.
No Bull Sharks in Canada (Or the Great Lakes)
You may have heard rumours over the past several years that bull sharks were well and multiplying in Lake Ontario. That’s false, pure and simple, despite what the National Post would have you believe in a satirical and, if you don’t mind me saying, irresponsible commentary from a national publication.
Bull sharks can indeed swim up rivers and live in lakes. We’ve seen this in several interesting situations, like sharks of Carbrook Golf Course in Australia. They’re fairly common in the southern United States as well, and have even been seen in the Mississippi River as far north as St. Louis.
But Bull Sharks don’t live in Canada, the St. Lawrence River, Ottawa River, Great Lakes and the many other places they’ve long been rumoured for several reasons, not the least being the same reason you wouldn’t jump in Lake Ontario on a frigid February morning: it’s too f***ing cold.
Bull sharks are a tropical species, and theoretically they could survive in the summer months in the Great White North, but as these biologists tell us, they can’t make it in the frigid winter temperatures we experience here in Canada.
Theoretically, yes, they could survive a few months in summer, but the Canadian winter is a beast of its own. Once the ice moved in, Mr. Bull Shark would be a popsicle, and that would be it.
A Great White Shark in the St. Lawrence Seaway?
This is doubtful. It’s true that great whites are making a comeback along the eastern seaboard and even stray into Maritime Waters. In fact, there’s even a minor hotspot for great white shark activity in Canadian waters at Sable Island, about 300 kilometres southeast of Halifax.
It’s also true that great whites have been seen in the Gulf of St. Lawrence. In fact, the second-largest great white shark ever measured was caught off Prince Edward Island in 1983 and made it to the esteemed ranks of ‘the world’s top 5 legendary sharks’ by Discovery Channel.
But great white sharks are oceanic creatures. There are no records of white sharks in the St. Lawrence seaway. It’s true they’ve been seen in estuaries, but it’s highly unusual for great whites to enter brackish water, and even less likely they’d travel so far inland away from their normal range.
Also consider that sharks are 2-3 times less buoyant in freshwater than saltwater. One study found a shark would need a liver about 8 times heavier just to stay afloat in a freshwater environment.
If a Great White Shark was in the Great Lakes, or St Lawrence River, it would need a liver clocking in at two tons, or twice its body mass, just to stay afloat.
So why can Bull Sharks survive in fresh water when other sharks can’t? Their livers are less dense than other shark species. And considering evolution takes millions of years, I doubt Great Whites will ‘develop’ resistance to freshwater anytime soon.
Here’s further proof Great Whites don’t enter the St Lawrence River (or Great Lakes). In mid-July 2019, a great white shark was tracked in the Gulf of St Lawrence, near the Magdalen Islands. His name is Brunswick and he was tagged several years ago by the research group Ocearch. But while he was indeed seen in the Gulf of St Lawrence, he was nowhere near the actual seaway.
Any guesses why? One reason, salinity. The second, buoyancy. Both would stop Great White Sharks in the St Lawrence River.
The Greenland Shark
Now that we’ve removed bull sharks and great whites from the equation, the St. Lawrence Seaway is actually quite rich in sharks. The greenland shark is the second-largest carnivorous shark on the planet – after Mr. Great White of course – that can weigh several tonnes and exceed 6 metres.
Greenland sharks are typically deep sea sharks, and spend most of their time in depths that can exceed 3,000 metres. Yet curiously, the mysterious beasts return from (presumably the Arctic Circle) to the St. Lawrence Seaway each summer – particularly around Baie-Comeau – with its much shallower water. It’s here that divers most often encounter this enigmatic sharks that feed, surprisingly, on seals and other creatures you’d think would require a speedy attack.
We’re still learning about greenland sharks and the role they play in Canada’s marine ecosystem.
The greenland shark is sensitive to sound. At this time, Greenland Shark Research (GEERG) does not recommend scuba diving with greenland sharks to reduce human risk posed to these fascinating creatures. That’s probably just as well for you, considering the challenges of diving in the St. Lawrence Seaway, but here’s a video of one such encounter.
**Update, March 4, 2018** In August 2017, a ‘Giant Shark‘ was recorded on video near Pasbebiac, Quebec, near the Gulf of St Lawrence. The catch? It was a Basking Shark – a harmless ‘Gentle Giant’ that feeds on plankton, and a welcome addition to the sharks that maintain the marine ecosystem of the St Lawrence area.