CHATHAM – With the board of selectmen slated to discuss the impact of seals – and sharks – on the town's beaches, fishing industry and economy next Tuesday, scientists say the issues are being clouded by misinformation and speculation about both species.
Some residents have sounded alarms about the increasing seal population and the resulting attraction of great white sharks to Cape waters. They say they are afraid to swim in local waters, even sheltered areas like Oyster Pond, because of the presence of seals and the possibility that sharks may also be lurking there. Two shark attacks this past season – a non-fatal bite of a swimmer in Truro and the death of a boogie boarder from a shark bite in Wellfleet – heightened the concern, and the rhetoric. Some are calling for culling of both seals and sharks, whose newfound abundance they see as unnatural due to federal protection of both species.
But scientists say what we're seeing is a restoration of a more balanced and healthy ecosystem following major disruptions, including the extirpation of gray seals in the U.S. after decades of bounties, the introduction of pollution into waterways and the devastation of a number of fisheries dating back as far as the 1800s.
“Seals have historically been here,” said Andrea Bogomolni, a scientists at the Woods Hole Oceanographic Institution and chairman of the Northeast Atlantic Sea Research Consortium (NASRC). “We have archaeological records, we have genetics that tell us the population was even more diverse than it is now, even if we don't have the numbers.”
There were no studies of seal populations prior to bounties being offered in Maine (from 1891 to 1945) and Massachusetts (between 1888 and 1962). According to a 2009 study in Northeastern Naturalist, an analysis of records show between 72,284 and 135,498 seals were killed in the bounty hunt, “probably enough to account for regional declines in seal populations.” The bounties came in two waves, from the late 1880s to the early 1900s and 1919 to 1962 in Massachusetts. Even though the bounty was in place through 1962, no bounties were paid in the state after 1959. However, the study found that indiscriminate killing of seals continued until the Marine Mammal Protection Act, which prohibits killing or harassing any marine mammal, was passed in 1972. It also found that even during periods when seal populations were low, fishermen still complained about the animal's impact on their livelihood.
Seals do eat commercial fish species, including cod and haddock, but those aren't necessarily their staple diet. Bogomolni said gray seals eat 38 different species of fish, and studies have found that their primary diet is sandlance, hake species and flatfish. She acknowledged there is interaction and competition between seals and fishermen, who have long blamed seals, which eat 4 to 6 percent of their body weight per day, for destroying fish stocks. But there's a lack of science in this area, and NASRC is working with fishermen and fisheries organizations to find answers. The group has a relationship with the Cape Cod Commercial Fishermen's Alliance, and this past summer worked with retired fishermen and representatives of the Atlantic White Shark Conservancy (AWSC) as pier hosts at the Chatham Fish Pier doing what Bogomolni called “myth busting,” educating visitors about seal, fish and shark facts.
Seals are mesopredators, below great white sharks – an apex, or top predator – and play a key role in the food web of the marine ecosystem, from controlling other predators to contributing and circulating nutrients through their feces that are important to the marine system, Bogomolni said. There's no evidence that seals contribute to marine pollution or beach closures, since most major haul-out areas, such as Monomoy, are away from public beaches and in environments with high tidal flushing rates.
Seals also embody something of a dichotomy. People are attracted to them; they bear a strong resemblance to dogs. Seal watches are big business on the Cape, part of a larger ecotourism, conservation and marine stewardship economy that a new study by University of Vermont researcher Joe Roman found contributed $179 million to the Massachusetts economy in 2014, more than commercial fishing ($105 million) and whale watching ($111 million). A study by Jennifer Jackman found significant opposition to lethal management of seals among tourists (most opposed), the general public and fishermen (least opposed).
The appeal of seals has created some difficulties. Seals have become acclimated to people and mill around at the fish pier and town landings looking for handouts and fish waste to snack on, even though feeding seals is a violation of the Marine Mammal Protection Act. Two people were nipped by seals at Ryder's Cove town landing in August. Bogomolni said those are learned behaviors, and it's up to people to change them.
“These are very smart animals, and I want to say very lazy animals” who will look for a handout. They should be treated like any other wild animal. “It's great that [people] want to associate [with seals]. It's something that comes from the heart. I get it. But at the same time, you wouldn't do it with a bear.”
Even if the Marine Mammal Protection Act could be somehow be amended to allow a seal cull, constant vigilance would be required to keep the population in check. That's because there's really no distinct Cape Cod gray seal colony, Bogomolni said. “We don't have Cape Cod seals,” she said. “We have a Northwest Atlantic population, with different breeding sites” – including Monomoy – “but the seals go in between.” The western Northwest Atlantic gray seal population is estimated at more than 600,000 individuals, with about 5 to 10 percent found on the Cape. According to NASRC, satellites have tracked gray seals swimming from Nova Scotia to Cape Cod in as little as five days. Studies have shown that unless the entire species is extinguished, culling doesn't really work, she added.
The current estimate of gray seals numbers in the U.S. is about 27,000, mainly reflecting breeding populations and not including seasonal changes. Estimates of 30,000 to 50,000 gray seals off the Cape is from a count done using Goggle Earth images and probably does account for greater numbers here seasonally.
There are other factors that could limit seal populations. In late summer, the National Oceanic and Atmospheric Administration declared an “unusual mortality event” after distemper was discovered in stranded harbor and gray seals. Those cases occurred in the Gulf of Maine and there has been no confirmed cases locally, but because of the mobility of seal populations, it's likely to show up here, Bogomolni said.
A number of seal studies are ongoing, according to Kimberly Murray, the leader of seal research team at the NOAA's Northeast Fisheries Science Center in Woods Hole. Every winter scientists take samples from gray seal pups on Muskeget Island and Monomoy and also fly drones to estimate the pup population. Every few years they also do aerial surveys to get an estimate of the total population; these are usually done in conjunction with scientists in Canada in order to get an overall picture of the Northwest Atlantic population, she said.
Scientists are also studying seal diet by looking at the contents of the stomachs of animals killed in fisheries interactions and through the fatty acid in seal blubber. Satellite tags are also used to track the movement of gray seals; this January researchers hope to tag 19 gray seals on Muskeget and Monomoy, she said.
“We have a couple of different things going on in different areas, and they vary depending on what we can fund in a given year,” Murray said. Funding for all the studies comes out of the agency's pool of money for marine mammal research; there is no dedicate source of money for seal research, she said.
Sharks clearly eat seals, as seen in numerous predations caught on video this past summer alone. Figuring how where those attacks are most likely to occur, and under what circumstances, is one element of the research being done by State shark expert Dr. Greg Skomal. Understanding those patterns could help beach managers determine how and when to close beaches to swimming.
Bogomolni suggested officials look to locations that have been through the same situation – historically abundant species returning after a period of decline – like California, where communities have learned to live with large numbers of sea lions and sharks.
“People have reached an understanding,” said Bogomolni, who is originally from the Bay area. “These are the oceans, these are the animals that are there, do I take a risk or not?
“We're not alone. We definitely should be reaching out to other people, especially to quell the fears and misinformation,” she said.
Meanwhile, the regional shark working group met last week to continue efforts to coordinate more “Stop the Bleed” training sessions, research shark bite medical kits and update shark safety talking points, signs at beaches and safety brochures, according to a press release from the Atlantic White Shark Conservancy.
Skomal hoped to get at least a couple more days on the water before ending his five-year shark population study this week. Last Friday, Skomal and his research team tagged an 11-foot great white shark off Nauset Inlet, the 16th shark to be tagged this season.
For more information about seals, visit nasrc.whoi.edu/faqs.