After just two-and-a-half years of research, Maine biologists are surprised at the number of great white sharks in the Gulf of Maine.

A report released by the Maine Department of Marine Resources this spring showed that 23% of white sharks tagged in Massachusetts – 60 sharks in all – have been detected by receivers in Maine since research on the species began here in 2020.

“We’ve detected almost a quarter of the sharks that currently have active transmitters. When you think of how small an area our receivers cover, that’s a lot. That’s a pretty high return,” said Maine State Shark Biologist Matt Davis. “This data supports the idea that there is quite a bit of (white) shark activity in Maine. This is going to be, from a scientific standpoint, a fairly important year.”

This summer, a coalition of biologists will focus on the coastline between Cape Elizabeth and Saco to optimize the state’s limited research equipment and because it is an area with a high level of human activity in the water, Davis said. The focus area also is located near the University of New England in Biddeford, which is contributing to the research.  

Two real-time receivers will instantly alert biologists and town officials of a passing great white shark – one off the coast of Crescent Beach State Park in Cape Elizabeth and another near the mouth of the Saco River. John Mohan, a shark biologist at UNE, also hopes to conduct drone surveys of islands in Saco Bay known to be gathering spots for seals, a chief food source for great white sharks.

Davis said much is still unknown about great whites moving along the Maine coast and it will take several years of data before biologists have an understanding of the distribution patterns of the species in the Gulf of Maine.

Still, the little bit of data collected to date is illuminating, he said. 

Already, biologists know a few Maine hot spots where white sharks are found: Hermit Island and Ragged Island near the Phippsburg peninsula. Archival receivers detected more than 10 individual sharks there in each of the past two years. The Hermit Island receiver detected 18 white sharks in 2021 and 11 in 2022. Ragged Island detected 11 in 2022.

“We have had a couple other locations where there’s been 10 individual white sharks detected when you combine data across years: Bailey Island (in Harpswell), Scarborough Beach, Kennebunk Beach and Wells Beach,” Davis said.

In 2020, following Maine’s first fatal shark attack, the state Department of Marine Resources started actively monitoring white sharks tagged in Massachusetts with buoy receivers placed off the Maine coast between Ogunquit and Boothbay Harbor, in addition to monitoring seals wounded or eaten by sharks, and confirmed white shark sightings. The department worked with biologists at UNE as well as those at nonprofits in Maine and Massachusetts.

In 2021, the Department of Marine Resources and UNE used grants from the Maine Outdoor Heritage Fund to purchase real-time buoys that were deployed last year. The two real-time receivers record data and alert biologists instantly with text messages of tagged white sharks that come within 500 to 1,000 meters of the buoy. An alert is also sent to the Sharktivity app run by the Atlantic White Shark Conservancy. 

Roughly 260 great white sharks have been tagged off the coast of Massachusetts by the White Shark Conservancy and Massachusetts state biologists, with 60 of those sharks detected in Maine. The number of tags that can be detected changes over time, because some go inactive.

Last year the state placed its one real-time buoy near Popham Beach State Park in Phippsburg, but the receiver used to detect tagged white sharks didn’t work properly because of poor cell service, checking in about every six hours rather than every minute. It detected a tagged white shark, a 9-foot female that swam past on Nov. 1 at 9 p.m.

UNE’s real-time receiver in Saco Bay detected only one white shark: An 11.5-foot female white shark that swam past at 5:39 p.m. on Sept. 17, 2022.

In addition, the state and UNE monitored around 30 acoustic archival receivers that store data that’s collected at the end of the season.

The real-time receivers cost between $12,000 and $15,000, and the archival receivers cost between $2,000 and $5,000, Davis said. There are no plans right now to tag great white sharks in Maine because of funding restrictions, but Davis hopes grants in the future will pay for that effort.

Seals are a primary food source for white sharks – particularly after the apex predators have migrated back to their summer grounds in the Northeast. Biologists know white sharks can be found in greater numbers at seal haul-out areas, but it’s not known how often or consistently this occurs. In Cape Cod and Maine, state officials advise the public not to swim near seals. 

“I know we see overlap between seals and sharks at the outer reaches of the Cape Cod National Seashore, but in other areas I wouldn’t say just because there are seals, there are white sharks. There are a lot of different factors,” said Kimberly Murray, a seal biologist based in Woods Hole, Massachusetts, with the National Oceanic Atmospheric Administration.  

Since the Marine Mammal Protection Act was passed in 1972, harbor seals and gray seals have been protected and the populations have increased. 

There are ledges used for harbor seal pupping up and down the Maine coast. These are surveyed in spring to estimate the size of the seal population, which as of 2018 was roughly 61,000, Murray said. At NOAA, Murray helps track individual harbor and gray seals to study movements and behavior using satellite tags.

Some haul-out areas for seals in Maine include Duck Island in Kittery, Stratton Island off the Scarborough coast, Boone Island off the York coast and halfway rock in Casco Bay, said Lynda Doughty, the executive director of Marine Mammals of Maine, which tracks seals between Kittery and Rockland.

In Saco Bay, seals are known to congregate around Ram, Stratton and Eagle islands, said Mohan, the UNE researcher. It’s here where he hopes to learn more about the areas where there is significant overlap between white sharks and seals.

“If over time we could develop a (seal) survey that could potentially match with the acoustic data that might be interesting. We might be able to answer the question: Are there more detections when there are more seals?” Mohan said. “At this time it’s hard to say one way or the other.”

Copy the Story Link

« Previous

Ask Maine Audubon: How do you keep mosquitoes out of a bird bath?

Next »

Birding: This time of year, the trees are alive with the sound of music