July 29, 2013 — Seals have a tendency to hang around boats and snatch fish from nets, and for centuries people fishing off New England would kill any seal they saw. Between the late 19th century and the early 1960s, the state of Massachusetts offered a bounty of up to $5 for every pinniped slaughtered. By 1972, harbor seals, once common on Cape Cod, were becoming rarer, and gray seals were all but wiped out. But that year Congress passed the Marine Mammal Protection Act, a law that forbids the killing, capture, or harassment of whales, dolphins, polar bears, manatees, seals, and similar animals—creatures that commercial hunting and other human activity had taken, in some cases, to the brink of extinction.
The act has been a tremendous success. In March 2011, a one-day count of gray seals in Massachusetts waters found 15,756 of them, compared to 5,611 in 1999. The National Oceanic and Atmospheric Administration estimates that the gray seal population in the Western Atlantic grew annually between 6 and 9 percent during the past three decades.
Seals are taking the blame for luring sharks, and at the same time the old resentment is flaring up among some fishermen, who say seals are harming the cape’s struggling fishing industry. Gordon Waring, a seal specialist at the NOAA, cautions that marine biologists don’t actually know how seals interact with fisheries, and so far there is no sign that they are eating more than their habitat can support. But it is clear that seals are attracted to fishing boats and piers, and fishermen who watch seals stealing fish from their nets justifiably resent the greedy creatures, which the Marine Mammal Protection Act says can’t even be shooed away (that would be “harassment”). Fish stocks, particularly of cod, are down, and while that’s mostly due to other factors such as decades of overfishing, seals are a visible target for blame. There has even been talk of a seal cull, and a Nantucket-based group calling itself the Seal Abatement Coalition is lobbying Congress to remove gray seals from the list of species covered by the Marine Mammal Protection Act. Seal culls are already a regular occurrence in Canada, which has historically had much larger seal populations.
When a tourist from Colorado was bitten by a great white shark last summer while swimming off Cape Cod, an excited media made predictable comparisons to the 1975 blockbuster Jaws. The 50-year-old man, who was fortunate to survive with bites to his legs but with all his limbs still attached, was the first human to be attacked by a shark in Massachusetts waters since 1936. As more sighting reports poured in, 2012 became Cape Cod’s “Summer of the Shark.”
We all love a good shark scare, but in this case the coverage wasn’t completely exaggerated. In 1974, when Jaws was filmed just off the cape on Martha’s Vineyard, great white sharks—known to marine biologists simply as white sharks—were rare, with one or two spotted in New England waters each year. In 2012, there were more than 20 confirmed sightings at Cape Cod beaches, and so far this summer two beaches have been closed temporarily after the sharks’ telltale dorsal fins were seen just offshore. Scientists have now tagged 34 great whites off of Cape Cod, and the data show the minivan-size fish sticking to a clear migration pattern—down south or out to sea in the winter and, like the Kennedys, back to the cape every summer.
Jaws aside, these sharks are not hunting unsuspecting vacationers. They’re after seals, which have soared in population in recent years thanks to a national conservation effort that has proven enormously successful—some might say too successful. The shark resurgence comes down to simple food chain economics, but it also shows how wildlife conservation can sometimes have weird and unpredictable consequences.