The first confirmed instance of a dusky shark preying on a seal off southeast Cape Cod was reported in 2023, and researchers have been closely monitoring the species\u2019 activity in the area since then, Winton said.<\/p>\n
\u201cWe\u2019re starting to see dusky sharks take advantage of [seals] and it\u2019s been going on for a few years,\u201d Chisholm said.<\/p>\n
Winton said the dusky sharks she\u2019s seen off Nantucket are 8- to 10-feet long, although the species can reach 12 feet in length.<\/p>\n
![\"Dozens](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/05\/FGVFGNESYBE2VOFQNNPWPNVTNI.jpg\")
Dozens of sandbar and dusky sharks gathered off the coast of northern Israel on Dec. 30, 2022.JACK GUEZ\/AFP via Getty Images<\/p>\n
Dusky sharks aren\u2019t new to Cape Cod \u2014 or to the wider region. <\/p>\n
The species was found in waters up and down the East Coast for centuries until they were heavily commercially fished in the 1900s, Chisholm said.<\/p>\n
Dusky shark numbers declined \u201cprecipitously,\u201d when the species was hunted for their long, sloped tail fins in the 1970s and \u201980s, said Gavin Naylor, director of the Florida Program for Shark Research at the state\u2019s natural history museum in Gainesville.<\/p>\n
\u201cTheir numbers have been so depressed we haven\u2019t seen them, but now their numbers are coming back,\u201d said Naylor, adding that it\u2019s \u201ctaken 40 years for them to recover.\u201d<\/p>\n
It took environmental protection legislation to help the sharks rebound, starting in the 2000s, experts said. The seals that the sharks rely on for food also recovered from over-hunting after the passage of Marine Mammal Protection Act in 1972, according to Chisholm.<\/p>\n
Now, gray seal populations are growing in areas \u201cwhere they used to be found,\u201d and scientists are \u201cseeing an overlap where the dusky sharks and the seals are occupying the same area off southeastern Cape Cod,\u201d Chisholm said.<\/p>\n
Because dusky sharks prefer warmer waters, they could be particularly active off Cape Cod this summer, according to Chisholm.<\/p>\n
The sharks recovered in the Florida region long before the current resurgence in the northeast.<\/p>\n
As the species began to rebound a couple decades ago, more sexually mature dusky sharks eventually made their way north to Cape Cod, Naylor said.<\/p>\n
Like great white sharks, dusky sharks can cause severe injury or death to humans because they are so large, he said.<\/p>\n
\u201cIf irritated, they could bite your arm off,\u201d he added.<\/p>\n
One of the most recent dusky shark attack fatalities took place off the coast of Israel<\/a> in April 2025, Chisholm said.<\/p>\n Besides that incident, there have been only a handful of documented dusky shark attacks in recent decades, Naylor said.<\/p>\n Great white shark bites have caused more fatalities over the years, according to Chisholm.<\/p>\n This summer, dusky sharks, seals, and humans will all be in the water together off Cape Cod, Chisholm said, so beachgoers must take precautions.<\/p>\n \u201cPeople have to respect the fact that the sharks are hunting there,\u201d Chisholm said.<\/p>\n His best advice?<\/p>\n \u201cDon\u2019t swim with the bait.\u201d<\/p>\n That means, if you see seals or even large schools of fish in the water, stay calm and return to the sand immediately, Chisholm said.<\/p>\n Dusky and great white sharks are known to swim close to shore in pursuit of seals.<\/p>\n \u201cThe seals are right there in the surf zone,\u201d he said, \u201cand that\u2019s what they\u2019re looking for, so they get that close.\u201d<\/p>\n Claire Thornton can be reached at claire.thornton@globe.com<\/a>. Follow Claire on X @claire_thornto<\/a>.<\/p>\n