MAIN-À-DIEU, N.S. — A great white shark tagged off Cape Breton during a research expedition in September could soon be a mother.
Chris Fischer, expedition leader and founder of Ocearch, said while it’s far too early to say for certain, there are signs Unama’ki — a massive, 4.3-metre, 942-kilogram female his team captured and affixed with two satellite tracking tags near Hay Island, off Main-a-Dieu— is pregnant.
Although it’s still unproven, the leading theory among Ocearch scientists is that a subpopulation of Atlantic great white sharks swims north to Nova Scotia in the late summer to feed on seals and possibly mate.
Most gradually make their way south for the winter, often lingering off the Carolinas or northern Florida until the water cools.
Unama’ki, however, made a beeline south after she was tagged on Sept. 20, swimming more than 3,000 kilometres to reach the Gulf of Mexico by Oct. 25. Helena, another Ocearch-tagged great white that travelled to Newfoundland this summer, has since joined Unama’ki in the Gulf of Mexico.
“So I’ve got two females that are mature animals that are kind of doing something this year that we’ve not seen from previous animals this early in the Gulf with big females — Helena is not as big as Unama’ki — but it is very interesting not so much that she moved south with purpose, but just how far south and then turning to the west that she’s gone with purpose. We haven’t seen that,” Fischer said. “It is interesting. I’ve had conversations with my scientists about it, trying to get my head around what it might mean. I think it’s a little too early to tell what it might mean.”
Fischer said a big clue will be if Unama’ki shows back up in Nova Scotia again next fall.
“If she successfully mated in the fall up there, she won’t return there next year because she’ll be pregnant. What we know with our pregnant white sharks is they — at least in the other oceans, in the Pacific and other places — won’t return to these fall aggregations because it takes them a year and a half until they can give birth.”
If Unama’ki — who is named after the Mi’kmaq word for Cape Breton, which roughly translates into “land of the fog” — is pregnant, she could lead researchers to the place where Canadian white sharks give birth, something Fisher calls “the Holy Grail of the science.”
He said great whites are most vulnerable during the first few years of their lives, so identifying the nursery is vital to protecting the species.
“If she shows us that, we’ll then move to that spot, try to capture maybe 20 baby sharks — these things are about four-and-a-half, five feet — and we’ll put this little tag on them that will work for about a year, a year and a half. Then they will define the nursery and where they’re moving in the nursery so we can make sure we’re not gill netting the birthing site of the Atlantic white shark and we don’t know it.”
Along with Sydney, Murdoch and Caper, Unama’ki was one of four sharks the Ocearch team managed to tag and collect multiple scientific samples from while in Cape Breton. The Nova Scotia expedition wrapped up off West Ironbound Island near Lunenburg, where they captured another seven sharks. Samples and data gathered from each of the 11 sharks will support 18 individual research projects by 32 researchers at 22 different institutions.
Fischer said his team is “champing at the bit” to return to Cape Breton next year.
He said their encounter with Caper was “really shocking” because she is the first small, juvenile female white shark they’ve ever observed in Canada. In addition to the four sharks they tagged here, they observed eight others, including a 5.2-metre male that spit out the hook before they could get it onto their cradle.
Fischer said Cape Breton seems to be a “bigger, mature white shark hangout.” The water temperature was unseasonably cold when they were in Cape Breton, leading him to believe there will even more activity when they return.
“If the data turns out to be what my gut feels like right now, Cape Breton will be a cornerstone of the puzzle. But I don’t have the data for that yet, but I can tell you that as a waterman who’s seen these things all over the world and handled hundreds of them, it’s a very significant place. I’ve got to go back there and see the place when it’s more normal, when it’s more average. We did not see what Cape Breton looks like in September nine years out of 10. We got the one odd year. We got the freezing cold year a month early,” he said.
“The situation with the water was so bad and then the situation with the sharks was still so good that I can’t imagine what it’s like when it’s peaking. We’ve gotta get back there when it’s just average.”
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