Photo: Contributed

Chris Fischer, founder of Ocearch and expedition leader, poses for a portrait aboard a ship on the water off the coast of Lunenburg, N.S., Thursday, Sept. 20, 2018.

Not far off Nova Scotia's rough-hewn shoreline, scientists on board an aging crab boat lay in wait for one of the marine world's greatest — and most mysterious — predators.

The researchers are busy "working the water" — dunking bits of fish in hopes of drawing a great white shark close enough to catch it and very carefully direct it onto their large boat.

Once they get a shark on board, the Ocearch team plans to afix it with several satellite tags that can collect data identifying everything from water temperature and salinity levels to its movements and feeding behaviours.

They're hoping the information can help them answer a central question — whether Nova Scotia may be a second mating site for Atlantic white sharks, something scientists say could be key to protecting the endangered species.

"We're up here trying to solve the puzzle of the North Atlantic white shark population," Dr. Bob Hueter, chief scientific advisor for the Ocearch expedition, said Thursday just outside the mouth of Lunenburg harbour on the first day of the team's three-week expedition.

"We're just beginning to unravel the mysteries of the white shark in the North Atlantic — where they're giving birth, their migratory patterns, where they mate, which is why we're here, and what they feed on."

The team was drawn to the area after one of Ocearch's tagged sharks — an adult male named Hilton, known for a wry Twitter feed that regularly tweets out his movements — ventured into the region last fall and then returned this year, suggesting he was here seeking out a mating partner.

Chris Fischer, the founder of Ocearch and the expedition leader, said white sharks are known to mate around Nantucket, Mass., and give birth off the south shore of Long Island, N.Y. But, he said Hilton and a female tagged shark named Lydia didn't go to those areas, indicating they may be spending their time mating in other areas.

"We believe he's showing us a second aggregation site and if we can find other mature males and other mature females, that might lead us to believe there's some mating going on here," he said on the Ocearch vessel, a former Bering Sea crab boat that now serves as the group's main research boat.

"Hilton knows where he is and what he's doing. He's not lost. These animals have an unbelievable capacity to navigate and a very accurate calendar. He's here for a reason."

Last week, federal scientists on a separate mission successfully tagged a great white shark in Atlantic Canadian waters for the first time.

The Ocearch team, which includes 26 researchers from 19 U.S. and Canadian universities and labs, hopes to catch a shark by hooking it onto a line held by crew on a smaller boat who will then try to lead the shark to the large Ocearch vessel.

They will try to guide the shark onto a submerged platform with the help of a crew member who jumps from the small boat into the water with the shark to secure it on the platform.