Most detailed map ever created of white sharks covers 6,287 sightings

A new analysis of tag detections maps the clearest picture yet of white shark presence along the Maine coast. The team compiled a decade of signals from tagged animals to show when and where these predators cruise local waters.

The results point to a reliable seasonal presence in nearshore areas, not just a few chance appearances. The dataset is large enough to change how managers, beach staff, and boaters think about Maine’s summer seas.

More than 100 white sharks are regulars

The study tallied 6,287 confirmed detections grouped into 728 events from 107 unique white sharks. The receiver coverage was expanded after 2019, and this added sharper detail to the map.

Most detections came from shallow water, with many events being recorded within about 0.6 miles (0.97 kilometers) of shore.

The team pooled data from multiple acoustic telemetry arrays deployed between 2012 and 2023.

Sharks showed up between May and December, with activity peaking from July through September. Many events occurred in water less than 65 feet (19.8 meters) deep, and the average nearshore event lasted about 14 minutes.

Several locations stood out. Head Beach on Hermit Island logged the highest count of unique sharks, while nearby Ragged Island recorded the most events per unit of receiver effort, suggesting concentrated use of parts of eastern Casco Bay.

How this changes the map

The tracks tighten the connection between Maine and known summer hotspots to the south. They show how sharks move along the shelf and use local pockets of habitat.

In the Western North Atlantic, these animals typically migrate seasonally from New England and Atlantic Canada to the Southeast and Gulf of Mexico as waters cool. A similar pattern has been documented by other researchers using satellite and acoustic tags.

Young-of-the-year white sharks center their first summer and fall in the New York Bight nursery before shifting range with age. This helps explain Maine’s mix of white sharks.

The Maine detections included mostly juveniles and subadults, along with some adults. This is consistent with a report that tracked the early movements of young-of-the-year white sharks in the Western North Atlantic.

Data suggest a white shark corridor

Warming matters as well. The sea surface temperature in the Gulf of Maine is reportedly rising faster than 99 percent of the global ocean, a backdrop that can alter seasonal timing and habitat use.

The new map suggests a corridor effect along western Maine, with some sharks pinging at four or more sites within a single day.

A subset returned to the same spots across years, suggesting that individuals are familiar with these sites.

Why summer brings white sharks

Food is a strong driver of white sharks to Maine. Gray seal colonies on the Northeast Shelf provide dense, energy-rich prey that attract foraging subadults and adults in late summer and early fall.

The pattern mirrors what researchers have tracked at Cape Cod and in Atlantic Canada. White sharks off Cape Cod spent almost half of their monitored time at depths shallower than 15 feet (4.6 meters).

This emphasizes just how coastal these animals can be during the summer foraging season.

“White sharks are regularly spotted off our coastline during the summer and fall, the peak of Cape Cod’s tourist season, but until now we didn’t know just how much time they spent in shallow water close to shore,” said Megan Winton, research scientist at the Atlantic White Shark Conservancy.

White shark movements

Maine’s detections followed similar water temperatures, with many events occurring when nearshore conditions hovered in the mid 50 to upper 60 degrees Fahrenheit (13 to 20 degrees Celsius).

That lines up with the thermal window reported for Northeast white sharks, as seen in a study on white shark movements in the Western North Atlantic.

Sharks did not linger long at most Maine receivers. The short event durations point to patrolling and brief passes rather than sustained residency at any beaches.

What this means for people

Risk remains low, even with a regular shark presence. The dataset indicates that nearshore detections cluster in summer and early fall, and that most events near beaches were brief.

Public interest in safety rose after Maine’s first recorded fatality attributed to a white shark, which occurred off Bailey Island on July 27, 2020. The report from the Florida Museum of Natural History documented the incident, the first confirmed fatality for the state.

White sharks are a prohibited species in all U.S. fisheries, which means they cannot be retained and must be released if caught. NOAA’s overview emphasizes their ecological role as an apex predator and notes increasing abundance trends in the Northwest Atlantic since the 1990s protections.

Local decisions, such as signage, drone patrols, or temporary swimming advisories during seal surges, can be informed by these timelines and hotspots. The point is not alarm, but awareness that patterns now exist and can be watched.

What scientists will watch next

Coverage gaps remain along Downeast Maine and offshore ledges. More receivers, plus tag types that log depth and temperature at fine scales, would tighten estimates of residency and movement.

Climate will keep nudging the puzzle. NOAA reports that warming seas and stronger storms shift prey distribution and alter habitat quality for sharks and rays, which can reshape where and when species show up on our coasts.

Understanding these shifts matters for fisheries, wildlife viewing, and emergency response planning. It can also inform habitat mapping and future revisions to management boundaries if consistent use emerges in places north of historic limits.

The Maine dataset gives managers a baseline. It also offers a practical way to brief lifeguards, harbor officials, and charter operators on what to expect in late summer along popular beaches and island outcrops.

The work was led by Matthew M. Davis of the Maine Department of Marine Resources, with collaborators from the Atlantic White Shark Conservancy, the University of New England (UNE), and NOAA Fisheries.

The study is published in Frontiers in Marine Science.

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