This summer, Cape Cod beachgoers might notice some very large shadows cruising just offshore. After decades of relative absence, dusky sharks are turning up again along Nantucket and the Cape's southeast shore. Aerial footage and a new peer-reviewed study show the big predators, often 8 to 10 feet long and capable of reaching roughly 12 feet, working the coastline and preying on gray seals.
Drone Footage Confirms Dusky Seal Predation
In July 2023, drone and eyewitness video captured a dusky shark killing and consuming a gray seal near Great Point. Scientists later published the encounter as the first confirmed case of a dusky shark preying on a seal in this region. According to the Atlantic White Shark Conservancy, the finding, now described in Environmental Biology of Fishes, is pushing researchers to rethink what role dusky sharks are playing in Cape Cod's coastal food web.
Scientists Urge Caution
Biologists stress that dusky sharks typically feed on fish and smaller sharks, but they are fully capable of taking human-sized prey, which means a single bite can be severe. As reported by The Boston Globe, New England Aquarium scientist John Chisholm is urging swimmers to "be shark smart" and to "not swim with the bait" that is, stay out of water where seals or dense schools of baitfish are milling around.
Protections Helped Bring Them Back
Dusky sharks were heavily targeted for their long tail fins in the 1970s and 1980s, and their numbers crashed to very low levels. Fisheries protections put in place in the 2000s, along with related management measures, have slowly allowed populations to begin rebounding. Scientific analyses note that directed harvest in United States waters was effectively prohibited around 2000, and the gradual recovery, combined with rebounding seal populations protected under the Marine Mammal Protection Act, has created the overlap that is now drawing these sharks into nearshore feeding areas, according to Animal Biotelemetry.
Rare but Serious Incidents
Documented dusky shark attacks on people remain rare, with experts citing only a handful in recent decades, but encounters can be dangerous when they do happen. A recent fatality off Israel in April 2025 underscored that point, serving as a reminder that recovering populations of large predators can change the risk landscape even if human encounters stay uncommon, as reported by BBC News and regional scientists.
How Researchers and Towns Are Responding
State and nonprofit teams are stepping up shark monitoring this season, using drones, tagging work, and public reporting tools to keep tabs on who is cruising the shoreline. Local officials plan to use the Sharktivity app and other alerts to keep swimmers and beach managers in the loop. According to WCVB, the Atlantic White Shark Conservancy, the New England Aquarium, and the Massachusetts Division of Marine Fisheries are coordinating tracking and public safety outreach for the summer.
How to Be Shark Smart
Officials say the basics go a long way. If you spot seals or large schools of baitfish, calmly head for shore. Avoid swimming at dawn or dusk, stay near lifeguards, and report any shark sightings to researchers when it is safe to do so. For more details on reporting and safety tips, check the guidance from NOAA Fisheries and local reporting tools.
