Victim of the caricature made of it by the cinema and of the myths maintained by the media, the great white shark has suffered for decades from an unenviable reputation. This large predator is, however, a crucial element of the biodiversity of marine ecosystems, and scientists want to understand what attracts these sharks to the Gulf of St. Lawrence, but also to discover if their numbers are increasing.
Researcher at the Maurice-Lamontagne Institute in Mont-Joli, Xavier Bordeleau returns from an annual work project on the waters of the Gulf of Saint Lawrence, in the Îles-de-la-Madeleine region. And for the first time, he explains in an interview, scientists were able to mark great white sharks with acoustic transmitters which will make it possible to follow their movements throughout the year.
“We were extremely surprised to be able to tag nine white sharks in Quebec waters,” he underlines, specifying that the success of such operations is not guaranteed.
“They are often described as merciless predators, but when you deploy the bait, you can wait up to a few hours before seeing sharks. And it may still take a long time before they are confident enough to approach it. They actually start by approaching the boat sporadically. As they gain confidence, they come closer and closer, to the point of passing close enough to the boat to be able to be marked,” explains the researcher.
The addition of these animals to the catalog of sharks carrying a transmitter is therefore good news for scientists at Fisheries and Oceans Canada. Until now, these are mainly individuals marked in American waters, in the Cape Cod region, which could be detected year after year in the waters of the Gulf of St. Lawrence between late spring and early fall. .
Thanks to the sharing of data between scientists and the presence of acoustic receivers in different parts of the Gulf of St. Lawrence, sharks are in fact identified every year in Quebec waters. In 2021, 19 of them were spotted in the area of Île Brion, located northeast of the Îles-de-la-Madeleine, out of approximately 200 receivers active at the time. “It was a first discovery,” recalls Xavier Bordeleau. In 2022, 42 were also identified near the archipelago’s gray seal colonies.
Some of these sharks are known and named individuals. This week, for example, the acoustic signal of Breton, a four-meter male weighing more than 1,400 pounds, could be captured off the coast of Percé. According to the information available on the Ocearch site, this animal also travels over large distances which are typical of its species, with migrations as far as the coast of the Bahamas, but also all along the American east coast.
Threatened species
The team of federal scientists of which Xavier Bordeleau is a member now wishes to continue marking efforts in order to better understand the behavior of this species and the habitats that would be essential to it in the Gulf.
It should be noted that the Atlantic great white shark is listed as “endangered” under the Species at Risk Act, after suffering a decline caused by accidental mortality caused by commercial fishing, but also because of its “trophy” character for certain sport fishermen. The federal government therefore has a legal obligation to protect it.
The researchers also hope to be able to answer a question that remains unanswered: are there more great white sharks today? “At this time, there is no scientific consensus on whether or not the white shark is more abundant in the waters of the St. Lawrence. There are some clues that suggest yes, but we must keep in mind the fact that marking and monitoring efforts have increased. It is therefore not easy to answer this question,” admits Mr. Bordeleau.
After decades of bad press caused largely by fiction films Jaws, the species is now better protected and population growth is possible. But as the species can take up to 30 years to reach sexual maturity, and therefore its ability to reproduce, a possible recovery would take several decades.
Ecosystem regulator
One thing is certain, their presence in certain areas of the Gulf seems to be linked to the abundance of a favored prey of the shark: the gray seal. A specialist in pinnipeds and the relationships between prey and predators, Xavier Bordeleau highlights that Brion Island is home to the second largest colony in the North-West Atlantic. Several seals injured or killed by sharks have also been found in this area.
In this context, could an increase in the presence of the large predator make it possible to reduce the seal herd, which has become overabundant with some 425,000 animals in Eastern Canada? “It’s a hypothesis that we are trying to verify. White sharks play an ecosystem regulatory role, since they are a large predator. And the overpopulation of seals was favored by the absence of natural predators. If there is a return of the white shark, it will be a good thing for the ecosystem,” explains Xavier Bordeleau.
The overpopulation of gray seals, a species that is currently not hunted sufficiently to reduce the herd, directly threatens the survival of certain fish species, including cod in the southern portion of the Gulf of St. Lawrence.
The scientific director of the St. Lawrence Shark Observatory, Jeffrey Gallant, and the general director of the organization ÉcoMaris, Simon Paquin, also believe that the presence of the great white shark is good news. Both took part this summer in the “Brion23 expedition”, organized by ÉcoMaris, to document the presence of the species in the area.
“Sharks are essential to the balance of ecosystems like that of the St. Lawrence. We must therefore work to deconstruct the myths that exist in popular culture about their dangerousness,” says Mr. Gallant.