With frequent sightings on the Cape, and several shark attacks, great white sharks have dominated the headlines in recent years, including this summer. But great whites aren’t the only shark species that swim in Massachusetts waters. Greg Skomal, shark researcher and senior fisheries scientist at the Massachusetts Division of Marine Fisheries, said about a dozen species appear off our coast during the warmer months.
“Some are common and some are uncommon,” said Skomal. “Some occur near the coast, and some are offshore, miles from land. Most are seasonal and tend to be here from around June to October.”
The least common visitors to Massachusetts waters are tiger sharks and hammerheads, Skomal said. They’re occasionally found near Martha’s Vineyard and Nantucket, sometimes close to beaches, but mostly in offshore waters.
“They’re more common miles from land, in the warm, clear, tropical waters of the Gulf Stream, at the edge of the continental shelf, which extends about 100 miles from the New England coast,” Skomal said. Fishermen sometimes encounter these shark species while fishing for swordfish, marlin, and tuna.
Aside from an occasional bite through fishermen mishandling sharks they’ve caught, very few of the species found in Massachusetts waters — other than great whites — have ever been identified in unprovoked attacks on humans, Skomal said. Tiger sharks have been involved in attacks, but not in Massachusetts.
Common species near shore include smooth dogfish and spiny dogfish. These species are small sharks that grow to about 3 or 4 feet long. It’s not unusual to catch them, Skomal said, although most people let them go. But there is a commercial market in Europe for spiny dogfish used in food like fish and chips, he said.
About 5 miles or more offshore, blue sharks are very common this time of year, said Skomal. They grow to about 12 feet long and weigh up to 500 pounds. And they live up to their name.
“They are a brilliant blue,” said Skomal. “Gorgeous.”
Another common offshore species is the shortfin mako, which is in the same family as great whites. Skomal said makos love to eat bluefish, and can grow to about 12 feet long and weigh up to 1,200 pounds.
“They’re a target species for recreational fishermen,” said Skomal. “Makos love to jump when you hook them, so they make an exciting catch.”
He said makos make good eating, and are caught by commercial longliners too.
Thresher sharks are also common in offshore waters. They are unusual looking because the upper lobe of their tail can comprise up to 50 percent of their 10- to 20-foot length. Threshers hunt by using their oversized tails to thrash schooling fish or squid, stunning or killing them. Skomal said threshers make good eating and are prized by recreational fishermen.
Another common offshore species is the porbeagle shark. Skomal said porbeagles look similar to mako and great white sharks. They feed on schooling fish like mackerel and herring, as well as squid, and can grow to be about 10 feet long and 500 pounds. Porbeagles can be found in New England waters year-round.
The largest common shark species in Massachusetts is the basking shark, said Skomal. Basking sharks are the second-largest fish species in the world, and can grow to about 30 feet long and weigh more than 5 tons. They are filter feeders, and swim slowly with their large mouths wide open, taking in water and sifting out small, shrimplike organisms called zooplankton.
Whale sharks, which can grow to more than 40 feet long and weigh 20 tons, are the largest fish in the world. Considered rare in our region, they are filter feeders that rely mainly on small, schooling fish.
Skomal said a few Massachusetts sharks, including sandbar sharks, dusky sharks, and sand tiger sharks, which can be found in nearshore waters, are protected through the National Marine Fisheries Service, and have what is called prohibited status, meaning they must be let go if caught by fishermen. Great white sharks and basking sharks have prohibited status as well.
Sharks are important because they are top predators in marine ecosystems, and they help keep those ecosystems in equilibrium, Skomal explained.
“Sharks play an important role in the ecology of the ocean,” said Skomal. “If sharks are removed, things could get out of check. Certain prey species would overpopulate and disrupt fisheries. It’s important to have well-balanced ecosystems.”
Don Lyman is a biologist, freelance science journalist, and hospital pharmacist who lives north of Boston. Send your questions about nature and wildlife in the suburbs to email@example.com.