Sharks may be mating on Georges Bank: biologist
Bites could impede findings
Marine scientists in Halifax believe they may have found a new breeding ground for sharks off the coast of Nova Scotia, but they have run into trouble trying to retrieve all the data they need to verify their suspicion that porbeagle sharks are mating around Georges Bank.
Marine biologist Steven Campana, with the Bedford Institute of Oceanography, said some electronic tags attached to large female sharks last summer as part of Canada's first-ever shark survey have been disabled.
"We suspect part of the reason is that if these tags are on during the time of mating, given that male sharks will often bite the females to hold them in position, we suspect that a few of our tags have been bitten rather fatally, which explains why we don't hear from them," Campana said.
"It is a very sophisticated and fun piece of technology — it's about the length of the palm of my hand. Inside this little unit is a remote sensor and processor," Campana said.
"So, this tag — pop-up tag it's called — is attached to the back of the shark and the shark tows it around for the next six or eight months. So we get an entire record of what that shark has been doing over a six- or eight-month period without having to recapture the shark."
The tag is programmed to detach from the shark on a certain date, float to the surface and then shoot the data to a satellite. But some never make it.
More than 850 sharks were caught last summer in waters on the border between between the United States and the southern coast of Newfoundland by fishermen, members of the Atlantic Shark Association, in conjunction with scientists from the Department of Fisheries and Oceans.
"They were all fishing in the identical manner — the same number of hooks, the same size of hooks, the same fishing pattern. So it gave us a snapshot of where the sharks were and, in a relative manner, how many were out there," Campana said.
Most of the sharks were kept to be sold at markets in the United States and Europe. But any large females were tagged and released because of concerns about reproduction.
Campana said with concerns about overfishing and declining populations, the survey found some positive indicators about the shark population.
"Speaking specifically around Georges Bank, there were some mature females caught that we simply didn't expect to be in the area. It made us suspect that there may be a second mating area for porbeagle sharks off our coast," he said.
Until now, researchers thought the only mating area for porbeagle sharks was off southern Newfoundland, Campana said, noting that area is closed to fishing as a conservation measure.
"If it turns out there is a second mating area, then I suspect there will be serious discussion to close that as well because everybody wants this shark population to recover," he said.
"We're still trying to confirm that, and we're just getting the results back from the satellite tags and hopefully this will answer the question."