When most of us imagine a shark, we picture something along the lines of Jaws’ famous antihero: a massive, blunt-nosed, white bellied monster: a great white shark. But great whites constitute only a tiny percentage of the world’s sharks, and New England has some incredible habitat for many of the other species that swim our seas. For example, out on Cashes Ledge—an underwater mountain range 80 miles off the New England coast that harbors some of the most incredible habitat in the Gulf of Maine—you might come across multiple fascinating species, among them the blue shark and the porbeagle shark.
The blue shark, a slender, blue-hued fish measuring up to 12.5 feet in length, often swims in schools organized by sex and size. This habit, along with the sharks’ tendency to use their schools as “packs” to heard prey into a concentrated group for easy feeding, has earned blue sharks the nickname “wolves of the sea”.
Blue sharks migrate up and down the Americas’ Atlantic coast, and may travel all the way from New England to South America in a migration year. They prefer cooler waters, however, and so are more likely to be spotted by divers in the colder north, because in these temperate waters blue sharks are more willing to approach shore. Blue sharks prefer water between 45 and 61 degrees Fahrenheit, and as New Englanders will ruefully agree, that makes them right at home here.
Squid constitutes a large part of the blue shark diet, but the sharks are not choosy, and hunt octopus, cuttlefish, bony fish, lobster, and even sea birds. Some blue sharks have been observed snatching cod from trawl nets. The sharks themselves are sometimes hunted by orca whales—coincidentally also nicknamed “wolves of the sea”—but their primary predators are humans. An estimated 20 million blue sharks are caught each year, both as bycatch in commercial fisheries and as a directly targeted species by commercial fishermen and sport fishermen. The blue shark is currently listed as “Near Threatened” by the IUCN Red List of Threatened Species.
Porbeagle sharks boast both a memorable name and impressive lifespan: around 65 years, which is more than triple the estimated lifespan of the blue shark. Shorter and bulkier than blue sharks, porbeagles have dark grey bodies, white underbellies, and rounded heads. They grow to around 11.5 feet and weigh about 300 pounds at maturity. Porbeagles are also migratory sharks adapted to cool waters, but they stay farther north and closer inshore than blue sharks do, feeding off the Canadian coast and migrating south to the Sargasso Sea to breed. They rarely swim more than 200 meters deep, yet, sadly, divers are unlikely to come across them—the IUCN Red List classifies porbeagles as endangered in the northwest Atlantic.
Due to its unique and productive landscape, a decade of protection from underwater trawling, and its location along the sharks’ migratory route, Cashes Ledge provides a perfect refuge for these incredible but threatened sharks. Divers admiring the kelp forests, anemone beds and schools of rare and threatened fish might be lucky enough to spot a pack of sleek blue wolves of the sea or a dark gray porbeagle as the sharks pause in their coastal migration at this sanctuary in the sea.