Seals are a sign of healthy waters, but what impact are they having on fisheries?
By: Jack Perry, Providence Journal
PROVIDENCE – July Lewis of Save The Bay sees seals as an indicator of environmental health, so she was encouraged when her organization recently counted 755 in Rhode Island waters.
“It tells us the bay is really healthy, and the coastal waters are as well,” said Lewis, Save The Bay’s volunteer and internship manager.
On March 27, forty-three volunteers fanned out along the shore and water at low tide to count seals in Save The Bay’s annual effort. They counted 551 in Narragansett Bay and 204 at Block Island. Save The Bay is a nonprofit organization, which defines its mission as promoting a healthy Narragansett Bay that is accessible to everyone.
The bay’s seal population has been steady over the past several years, while the Block Island population has increased, according to Lewis.
“Despite the breezy conditions, the seals were out there enjoying the sun, reflected in a well-above average number for the bay and coast, and the most we’ve seen yet for Block Island,” Lewis said in a Save The Bay news release.
Block Island has seen a big increase in seals
The Block Island count of 204 seals this year was up, from 131 last year. In 2021, just 16 seals were counted at Block Island.
Protected by the Marine Mammal Protection Act, seals started returning to Narragansett Bay in the 1990s, according to Lewis, and in 2009 Save The Bay began counting seals in the bay and along the coast. In 2019, Block Island was added to the count. (There was no count in 2020 due to the COVID pandemic. The 2015 count was canceled because of ice.) Save The Bay was able to expand its count to Block Island and get a “comprehensive count for seals statewide,” thanks to support from the Nature Conservancy on Block Island, according to Save The Bay.
“While the harbor seal population in the bay seems to be relatively stable, our volunteer monitoring efforts indicate an increasing number of gray seals on Block Island,” Lewis said. “This will be an interesting trend to watch in the years to come.”
Two types of seals spend time in Rhode Island’s Narragansett Bay
Harbor seals, which grow up to 6 feet long and weigh up to 285 pounds, are the predominant species in Narragansett Bay. Volunteers counted 549 harbor seals in the bay this year and two gray seals.
Gray seals, which can grow up to 10 feet long and weigh up to 880 pounds, are the main species at Block Island. Volunteers counted 160 gray seals and 44 harbor seals there.
Harbor seals play “an essential role in the bay’s ecology as a top predator species,” according to Save The Bay. Harbor seals leave the bay and head north in the warmer months, according to Lewis. Gray seals can be found in Rhode Island’s coastal waters year-round.
While some Rhode Islanders are still surprised to discover that Narragansett Bay has seals, Save The Bay’s seal tours are popular, according to Lewis.
“It’s really fun to see these big, charming animals right in our bay,” Lewis said. “It’s the most enchanting thing.”
Still, Lewis acknowledges that some Rhode Islanders aren’t as enchanted with seals as others. Seals eat a lot of fish, causing concern for some fishermen. Seals off Cape Cod have attracted great white sharks, and some worry that an increasing population will draw more sharks to Rhode Island waters.
What impact are seals having on fishing?
The Rhode Island Department of Environmental Management is trying to measure the seal populations’ impact on fisheries, but it’s challenging in part because seals are so mobile, with tagging studies “tracking them moving between Block Island, Long Island Sound, Cape Cod Bay, and the Gulf of Maine,” according to Scott Olszewski, the DEM’s acting chief of marine fisheries, and Tara Plee, the DEM’s principal marine biologist.
“These generalist predators adapt their diet based on prey availability, such as squid, sand lance, skates, and flatfish, which, along with their wide-ranging movements, makes it difficult to determine their exact impact on local ecosystems and fisheries,” Olszewski and Plee said via email.
“Seal interactions with fisheries are becoming more common. In some areas and seasons, fishing and survey work have been suspended due to seal interference. Seals have learned to raid floating fish traps in the fall and access bait in lobster traps, making them ineffective,” Olszewski and Plee said.
“While the operational impacts are evident, quantifying actual losses is difficult” and will require more study, some of which is dependent on additional funding, according to Olszewski and Plee.
Fisherman: Seals have “voracious” appetites
Chris Brown, 57, who fishes out of Point Judith on his 45-foot Proud Mary, said, “I’ve never seen so many seals in my life.”
“Seals don’t eat potatoes,” Brown said. “They have voracious appetites.”
Brown suspects the seal population off the Rhode Island coast and Block Island is linked to the “overpopulation” of seals on Cape Cod.
Brown, who is president of the Rhode Island Commercial Fishermen’s Association, has seen seals “munching on 20-pound striped bass.” He understands the seals are doing what they must to survive and believes he has no more right to the fish than they do.
Still, he has also seen more sharks than ever in Rhode Island waters, and he believes seals themselves, which can bite, could pose a risk for children swimming nearby.
“I really think we should manage their population before we have a problem,” Brown said.
Are seals attracting sharks to Rhode Island?
The waters off outer Cape Cod have attracted tens of thousands of seals and, as a result, hundreds of adult great white sharks spend their summers off Cape Cod, feasting on the fatty seals, according to Jon Dodd, founder and executive director of the Atlantic Shark Institute in Wakefield.
Dodd studies sharks in Rhode Island waters and along the East Coast. He’s also working with several other agencies to determine the seal population’s impact on shark behavior around Rhode Island.
The Atlantic Shark Institute monitors shark movements with acoustic receivers on buoys off the Rhode Island coast. As of now, Dodd hasn’t seen evidence of an adult great white shark taking up residence in the water off Rhode Island.
The large, adult great white sharks that Dodd’s equipment detects in Rhode Island waters are passing through “basically on a migration to the Cape and points north,” Dodd said. Smaller, sub-adult white sharks may stay in the area, avoiding Cape Cod, because they’re not big enough to take down seals, and they want to avoid becoming prey of the larger sharks, according to Dodd.
At what number, Dodd asks, might the seal population in Rhode Island grow large enough to prompt those sharks to take up residence here?
“Right now, we don’t have that, and I hope we never do,” Dodd said.