Growing concerns over great white shark boom off Cape Cod

Experts say the increase in sharks is due to the growing population of seals.

ByABC News
June 28, 2017, 11:40 AM

— -- An influx of great white shark sightings has residents and tourists worried about potential encounters in the water, especially during the heart of summer.

Senior Fisheries Biologist Dr. Greg Skomal told ABC News the increase in the great white shark population off the Massachusetts coastline is correlated to the gray seal population and that numbers are expected to rise even further.

"We've been studying sharks off the coast of Massachusetts for 30 years and our work with white sharks off Cape Cod is relatively recent," Dr. Skomal said on "Good Morning America." "The numbers we're seeing on a relative scale are increasing, in 2014 we counted 80 individuals over the course of the summer and just last summer that went up to about 147. So there is a general increasing trend as more and more sharks recruit to the area."

This season at least six great white shark sightings have already been reported, including a recent sighting off Wellfleet on May 9.

The National Park Service for Cape Cod has issued alerts to heed advisories at beaches to help ensure safety "particularly regarding white sharks."

Skomal believes the influx of sharks is a direct result of the growing seal population. "We think it's highly correlated with the growing presence of gray seals in the area. Big white sharks like to feed on gray seals. Over the course of the last 45 years, the gray seal population is a conservation success story. It has rebounded after protection was put in place in 1972 and that rebounding population now has reached levels that could be an excess of 20 to 30,000 animals in the area and white sharks are drawn to those areas to feed on them."

Awareness and education are key tactics to protect the public as well as the animals. Research from the Massachusetts Division of Marine Fisheries, Atlantic White Shark Conservancy and the National Parks Service about the biology and behavior of these sharks has helped inform seashore staff and beachgoers about best practices to stay safe.

"When you've got large numbers of sharks, the prey they feed on [seals] and people in the water, the potential of an interaction is there," Skomal said. "You want the people to be aware of it and that's really what our goal is. Collect the kinds of data to inform the towns so they can enhance public safety."

The National Park Service has an entire page dedicated to shark safety and includes what to do if you see a shark whether a lifeguard is on duty or not. There is even an app to report sightings.

And although encounters have become more common, Skomal explained that attacks are extremely rare.

"A silhouetted seal at the surface might look like a swimmer or vice versa, and what happens is the shark will do a test bite or attack the swimmer thinking it's a seal," Skomal said.