Jim Britt, communications director with the Maine Department of Agriculture, Conservation and Forestry, holds a flag at Crescent Beach in Cape Elizabeth in 2021. That flag is raised at Maine beaches if sharks are detected nearby. Robert F. Bukaty /Associated Press file

Great white sharks appear to be using the shallow coastal waters next to some of Maine’s most popular beaches in late summer while traveling between Cape Cod and Nova Scotia, most likely snacking on the growing seal populations in the Gulf of Maine.

A team of New England scientists documented 107 white sharks off the coast of Maine, ranging from 7 to 16 feet in length, between 2012 and 2023, with most detected within a half mile from shore in less than 65 feet of water, according to a study published last month in Frontiers in Marine Science.

But the total number of white sharks in Maine remains very low compared to known hotspots like Cape Cod or Hilton Head, according to the study’s lead author, Matthew Davis of the Maine Department of Marine Resources. On average, Maine beaches had a tagged white nearby less than seven days a year.

The relatively low numbers led the research team to conclude that Maine swimmers aren’t at significant risk and, despite the documented presence of white sharks in the Gulf of Maine, there is no justification for regional anti-shark measures, like shark nets, even along Maine’s most popular beaches.

While most whites are not tagged and come and go without setting off the acoustic sensors, the data gives researchers a new picture of white shark prevalence and movements along the Maine coast.

“We know a lot about white sharks in Cape Cod and Nova Scotia, but the Gulf of Maine has been sort of a black box of information up until now,” Davis said. “This is the first time anyone has been able to track the movements of white sharks over time in the region.”

After a white shark killed a woman swimming off Bailey’s Island in Harpswell in 2020 —Maine’s only fatal shark attack on record — the Maine Department of Marine Resources launched a white shark study team and deployed acoustic sensors along the coast to track the activity of already-tagged white sharks.

The department placed a sensor — think of them like a barcode reader with a big range — near sandy beaches, populated islands and seal haul-out sites, where the favored target of hungry adult white sharks are known to come ashore to rest, molt, breed and have pups.

The sensors show white sharks like the same sandy beaches we do, including Ogunquit, Kennebunk, Higgins and Wells. In an average year, Ogunquit attracts seven tagged sharks over five days, compared to Kennebunk’s six sharks in six days, Higgins’ five sharks in five days and Wells’ five sharks in four days.

And many like to go when we do. Nearly half the sharks were detected near beaches visited during the daytime. Their numbers start to surge in June and drop off in October, preferring water that is between 55 and 60 degrees Fahrenheit, although some will stay through December.

But it is important to note that the average shark detected near a Maine beach only hung out for about 15 minutes, Davis said. The average time spent out in the waters off Maine islands tended to be a little bit longer. In one rare case, a white shark hung out off the coast of Saco for more than a day.

A private beach open to the public at the southwest tip of the Phippsburg peninsula — Head Beach — appears to be the most popular among white sharks, attracting 40 different whites over a three-year period, the study found. Sensors there detected an average of 17 sharks a year over 13 days.

Surprisingly, nearby Popham only averaged three sharks a year, while Reid averaged only two.

Ragged Island in eastern Casco Bay — notable as the one-time summer home of poet Edna St. Vincent Millay — reported the highest number of days of shark activity a year, with 12 sharks visiting over 30 days. Ragged is close to haul-out sites where seals come ashore to rest, breed and have pups.

White sharks are not new to the Gulf of Maine, Davis said. Their numbers here are likely bouncing back because of conservation measures put in place for both white sharks, which were overfished until the 1990s, as well as seals, a favorite prey species for adult whites.

Maine is located between three of the largest gray seal colonies in North America, with pupping surveys indicating a growing population in the region. Within the last decade, the harbor seal population has grown to more than 61,000. 

Like many of Maine’s terrestrial visitors, white sharks tend to stick to southern and midcoast Maine locations. With one exception, no more than seven sharks were detected at any one Downeast location. Fewer acoustic receivers in these areas might help explain the relatively low detection rates.

The sensors can detect a tagged shark up to 2,000 feet away. That means a tagged shark at some of Maine’s longest beaches, like Ogunquit or Wells, could be missed. Most importantly, the study cannot paint a full picture of the white sharks in Maine because most of them aren’t tagged at all.

Davis said he would like to deploy more sensors in Downeast waters in the future.