Cape Cod’s Seal Problem
The population of gray seals on the Cape has exploded in recent years. Is it time to cull the herd?
A few summers ago, after my family and I had moved to Cape Cod from the Washington, DC, area, we were introduced to an unexpected treat: seal watching. Plopped on our chairs at Nauset Beach, a short drive from our home, in Orleans, we watched groups of cute gray seals frolicking offshore. Other beachgoers joined us in this happy pastime. To behold a seal’s face when it bobs up out of the water—those large, imploring eyes; that splay of whiskers; the dark, glistening nose—is to have the feeling you’re looking at a lovable Labrador retriever, with flippers. Seal watching is so popular around here, in fact, that special tours are offered out of Chatham. “Seeing these adorable mammals in their natural habitat,” one tour operator promises, “will make your family vacation one to remember.”
Not everybody loves the local seals, though. “Wolves that went into the water” is what my neighbor Bill Amaru calls them. Amaru is a fisherman who operates his boat out of Chatham harbor and has been working the Cape waters for a living since the early 1970s, when he was just out of college. He began noticing seals in the late 1980s, and then watched as their numbers gradually increased over the years—until the mid-2000s, when the population exploded. These days, he says, he can see between 4,000 and 5,000 seals on a single fishing trip in the area around Monomoy Island, south of Chatham. The National Marine Fisheries Service very crudely estimates that nearly 16,000 seals now inhabit the Cape and Islands, and one local marine biologist, Betty Lentell, who works with the Cape Cod Commercial Hook Fishermen’s Association, projects that the population will grow at a rate of about 20 percent annually for the foreseeable future.
That’s a lot of seals. And they all love to eat seafood, including the kinds of fish—striped bass, bluefish, and cod—sought out by area fishermen and local restaurants. According to the National Marine Fisheries Service, gray seals consume between 4 and 6 percent of their weight per day. A mature male can weigh 800 pounds and up, which translates roughly into a daily diet of 32 to 48 pounds of seafood—an amount that, multiplied by thousands, has fishermen concerned, especially since the rise of the seal population in the area has coincided with a precipitous decline in fish stocks.
The burgeoning seal population isn’t the only thing decimating those stocks, of course. Global warming has led to higher temperatures and increased acidity in local waters, which has reduced the biomass, such as plankton, that sustains fish populations. Commercial fish stocks have suffered from the predations of dogfish, too, the numbers of which have been rising in recent years. But the most significant cause—decades in the making—is human overfishing. Strict quotas are now in place to help stocks rebound, but many populations are so depleted that fishermen can’t even reach the quotas. And not surprisingly, they’re unhappy about sharing the fish that are still out there with a rapidly growing population of seals.
Seals also attract sharks—including the mightiest of them all, the great white, for which a gray seal is a superb high-calorie meal. Greg Skomal, the principal investigator for the Massachusetts Shark Research Program, recently discussed the relationship between seal and shark numbers at a symposium in Chatham. Twenty-one great-white sightings were reported in 2012, up from only four in 2004, before which whole years would often pass without any sightings at all. And just last summer, off Ballston Beach, in Truro, a great white bit a swimmer on the leg.
“We have a direct relationship,” Skomal told an audience of marine biologists, fishermen, conservationists, and local residents. “If you open up the café, the predators will come.” Given how easy it is for a shark to mistake a person for a seal, Skomal has even started to worry about the wisdom of letting people swim in areas populated by seals. “I’m not sure I would allow my son to swim in certain parts of eastern Cape Cod,” he told me on the sidelines of the conference.
Add it all up, and you’ve got what more and more Cape residents are now delicately referring to as “the seal problem.” During the Chatham symposium, Greg Early, a marine biologist representing the Northwest Atlantic Seal Research Consortium, raised the question that’s increasingly been on everybody’s mind.
“How much of a good thing,” he asked, “is too much?”
On a chilly Sunday this past April, I took a trip to Muskeget Island, on Nantucket Sound, in order to have a look at a big seal herd myself. Muskeget is the single largest breeding ground for the gray seal in the region. I rode out in a small motorboat with Crocker Snow, who owns a cottage on the island. Snow, the director of the Murrow Center for Public Diplomacy, at Tufts’ Fletcher School, is something of an anti-seal activist. He calls Muskeget’s seals “golf-course geese,” because of how they poop everywhere, and he worries that they’re upsetting the ecological balance on the island by fouling several small freshwater ponds and trampling the habitat and nests of the beach vole, a small rodent unique to the island.