Death of two great white sharks off the Maritimes in a matter of weeks is ‘highly unusual’: researcher

The discovery of two dead great white sharks in Atlantic Canada in less than two weeks is a mystery to researchers.

Fred Whoriskey, executive director of the Ocean Tracking Network at Dalhousie University, called the stranding of two of the ocean’s apex predators abnormal.

“Over the course of my life, and that’s many years, there have been fewer than five white sharks that I’ve ever heard of on the beach anywhere in the North American area,” he said in an interview. “So this is a very unusual event.”

The Marine Animal Response Society said in an Oct. 21 social media post that a great white shark had been found dead in New Brunswick’s Kouchibouguac National Park the previous weekend. The organization studies marine animals and helps with rescues and research.

The 3.4 meter mature male was found on the beach and samples were collected to aid in the study of the species.

Whoriskey, who is not involved in necropsiing the animals, said a second great white shark found dead Wednesday in North Sydney, NS, was a juvenile.

The great white shark is listed as endangered under the federal Species at Risk Act. There are no estimates of the size of the population in Atlantic waters, according to the website of the federal Department of the Environment. There are about 100 records of great white sharks sightings off the Atlantic coast since 1874, although sightings are increasing, with more than 40 since 2009, the website added.

The death of two sharks in such a short time could be a sign that the numbers of these animals are increasing, Whoriskey said. Most of the sharks seen in Canadian waters tend to be juveniles, which is one of the indicators of a growing population.

“It’s quite possible that we expect to see things like natural mortality more often because, like it or not, things are going wrong in biology.”

Whoriskey said that white sharks have no predators in Atlantic Canadian waters. “So we’re probably looking at natural causes for these two animals. Which is an interesting phenomenon.”

The images of the sharks, he said, do not suggest that they were killed by a collision with a ship or by entanglement in ropes. The animals could have died from a virus or bacteria, which could be investigated in the necropsy process, she said. But that’s not easy because scientists don’t have a good idea of ​​the kinds of diseases white sharks get.

“If we don’t know what we’re looking for, we don’t yet have a probe to detect it. It may be a pathogenic organism that hasn’t been identified by science yet. That could be something intriguing.” Whoriskey said.

Boris Worm, a professor of marine conservation biology at Dalhousie University, said great whites are found as far away as Newfoundland. They are typically in Canadian waters in the late summer and fall, he said, “probably going after some prey species in our region, like mackerel.”

The biggest risk to the species, Worm said, is humans.

With fishing trawlers, a shark on a hunt might not notice the trawl and get caught, potentially leading to its death, he said.

And longline fisheries take out lines baited with hundreds of hooks. Sharks with their remarkable olfactory senses can smell this from a distance and are drawn to it, she said.

“These fisheries typically have a large shark bycatch,” he said. “They don’t usually bring white sharks on board because white sharks bite the line if they get caught and escape. But they have occasionally been reported in longline fisheries.”

This report from The Canadian Press was first published on October 28, 2022.


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