The Associated Press
BOSTON–The movements of great white sharks in the Pacific and Indian oceans long have been the subject of academic study, but new research is just starting to shed light on the behaviour of their Atlantic Ocean counterparts.
Researchers in Massachusetts say white sharks appear to venture offshore farther, with more frequency, and at greater depths than previously known in the Atlantic.
Some of the 32 sharks tracked between 2009 and 2014 ended up as far east as the Azores, the Portuguese island chain located more than 3,700 km from Cape Cod, where most of the animals initially were outfitted with satellite tags.
They also were found to make frequent deep dives–as far down as 1,127 metres–and spend more time at those dark depths than previous studies in the Atlantic suggest.
The team, which included scientists from the state Division of Marine Fisheries, the Massachusetts Institute of Technology, and the Woods Hole Oceanographic Institution, had its findings published last week in Marine Ecology Progress Series, a prominent scientific journal.
“Everything we knew previously indicated that the white shark in the Atlantic is more coastally-oriented, moving north-to-south and remaining on the continental shelf,” noted Gregory Skomal, the study’s lead author.
“So what we’re now describing is this other component–this offshore movement into open ocean.”
Skomal said the work has implications for shark conservation efforts since it extends the known habitat for these ancient predators.
White sharks are not considered endangered or threatened, but it’s illegal to hunt them in U.S. waters.
“You’ve got U.S. protection within 200 miles of shore, but you have sharks clearly leaving that protection that are vulnerable to harvest,” Skomal noted.
“We need to engage other countries fishing in these waters to talk about putting similar protections in place.”
The research is exciting because it represents the “first real insights into the movement patterns of white sharks” in the northern part of the Atlantic, said Tobey Curtis, a Massachusetts-based shark researcher for the U.S. National Marine Fisheries Service who was not involved with the study.
“Prior to this, we were only able to piece together information about their distribution from widely-scattered reports from fishermen, scientists, and the public,” he noted.
“Having tracks of individual sharks really helps fill in the gaps, and provides a more complete picture of white shark movements and migrations.”
The study seems to hew closely to what’s been observed of white sharks in other oceans–that juveniles tend to stay in the relatively shallower waters of the continental shelf where food sources abound while adults are more apt to venture into open ocean.
Another key question is finding out what these sharks actually are doing so far offshore.
Researchers in northern California suggest offshore movements are for mating–a ritual that’s never been observed among white sharks.
But Skomal and his team believe the animals more likely are foraging; it’s just not immediately obvious what they’re feeding on.
“That’s the great mystery right now,” he said.