Waters off SE coast fill with great white sharks in winter, but no one knows why — yet

Great white sharks have a mysterious habit of moving south along the East Coast for winter, and scientists aren’t sure what drives this mass migration.

Is it a search for warmer water? Is it about mating? Or are the voracious predators chasing food?

Finding reasons for this “winter residency” is the goal of an OCEARCH expedition that will spend Nov. 28 through Dec. 14 hunting white sharks off the coasts of North Carolina and South Carolina.

It will include representatives of 30 research institutions, working on two dozen different shark studies, OCEARCH said in a news release.

“This is our first expedition trying to sample these white sharks as they arrive in their overwintering habitat period,” OCEARCH Founder Chris Fischer said in the release.

“It will allow us to understand the physiological makeup of a white shark in this region at this time, filling in the gaps to understanding their lives across their entire migratory path.”

The team intends to catch as many sharks as possible, then collect blood, fecal and muscle tissue samples, and perform ultrasounds on mature females.

None of those tests will be easy, considering great white sharks can exceed 14 feet and are uncooperative patients.

“Animals sampled during this time will provide valuable information about prey preference, foraging strategies, habitat use and preferred oceanographic features,” OCEARCH Chief Veterinarian Dr. Harley Newton said in the release.

OCEARCH, a nonprofit shark research agency, discovered sharks were gravitating to the region with the help of satellite tags attached to white sharks caught in the Northwest Atlantic.

Tracking data later revealed Dec. 1 through May 15 was an “overwintering period” when those sharks moved between Cape Hatteras, North Carolina, and Florida’s Gulf Coast, OCEARCH says.

It was long assumed they simply preferred warmer water, but that doesn’t explain why some tagged sharks were tracked as far west as the mouth of the Mississippi River, OCEARCH says.

“There is also variability in whether white sharks that move into the Gulf of Mexico go there each year or only on certain years,” Newton said. “There is still a lot to be learned about white shark movements in this region and season.”

This story was originally published November 23, 2022 at 1:20 PM with the headline "Waters off SE coast fill with great white sharks in winter, but no one knows why — yet."