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Cape Cod’s Seal Problem…

Photo Credit: Wayne Davis, oceanaerials.com

“I grew up fishing the Cape and I’ve watched the seal population grow over the years and completely decimate surf fishing on the back beaches from Race Point to Nauset,” said Matt Perachio of Tighten Up Charters out of Provincetown. “Nobody’s fishing off those beaches anymore.”

“Ten years ago, we never saw seals, but now they’re everywhere,” said Willy Hatch, who’s been fishing the Cape and Islands for over 25 years as the captain of Machaca Charters in Falmouth. “They’re at Squibnocket Beach, Vineyard Sound, the Elizabeth Islands, Woods Hole, the Muskeget Channel. Often, the seals hear me anchor up and set up behind my boat. If I manage to hook a fish, a seal takes it right off my line. It gets worse every year as their population increases and their range expands.”

Mike “Boz” Bosley has fished the waters around the Cape for 40 years. For the last 10, he’s been out there every day since he started Dragonfly Sportfishing in Orleans. “The loudest complaints I hear about seals come from shore-based striper fishermen. I do see a big difference in the abundance of bass in their traditional habitats, like the shallower waters on the flats early in June on Cape Cod Bay and down on Monomoy all summer long. The fish don’t come in close anymore. The seals are right there on the beach.”

Monomoy Beach Seals

An abundance of gray seals lining the beach on Monomoy in August 2017. Pilot and photographer Wayne Davis, who has been taking aerial photos around the Cape for 48 years, notes that the number of seals on the Cape seems to have declined during the last two summers.

Buddy Vanderhoop, a member of the Wampanoag tribe of Aquinnah, has run Tomahawk Charters out of the Vineyard for 32 years. In the last five or six, he’s seen countless stripers taken off the line by seals. “They see fish struggling, so if I don’t get them in the boat quickly, they’re going to eat them. Once a seal breaks a fish off the line, it usually comes up to the surface and eats it—starting with the head—right in front of me.”

It’s a fact. The seal population in Massachusetts waters has increased dramatically over the last 10 years, and Cape Cod and the Islands are ground zero for a growing conflict between striper fishermen and seals. If you think reports of seals are exaggerated, just go to YouTube and search “seals Monomoy.” Look for a video shot by Aaron Knight from a plane that shows what looks from a distance like a dark bathtub ring on the sand near the edge of the water. A closer look reveals an unbroken line of thousands upon thousands of seals going on for miles.

So, what’s going on? Is the seal population ballooning out of control? Are the seals putting a dent in the striper biomass? Or are they just causing the fish to move elsewhere while fishermen mourn the loss of formerly productive fishing spots? And what can we learn from marine biologists studying the diet and behavior of the seal population? The best place to start is to put the current state of the seal/striper conflict into historical context.

Great White Shark Cape Cod

A shark gives chase to its quarry just beyond the breaking surf on Monomoy last November. That seal managed to make it safely to the beach. (Wayne Davis, oceanaerials.com)

Seals Make a Comeback

Most fishermen are familiar with the remarkable comeback story of striped bass. Forty years ago, the striper fishery up and down the East Coast was in bad shape as a result of overfishing and industrial and agricultural pollution in the spawning waters of the Chesapeake Bay and the Hudson River. As Matt Perachio remembers, “In the early 80s, it was rare for anyone to catch even a small striper on the Cape. When someone did, we went to look at this fabled unicorn of a fish.”

It took the Atlantic Striped Bass Conservation Act of 1984, requiring all 15 states on the East Coast to comply with a stock management plan from the Atlantic States Marine Fisheries Commission (ASMFC) and a moratorium on fishing in the Chesapeake to jumpstart the fishery. The late 1990s and early 2000s were the glory days of striper fishing, but in the last decade, striper landings have been trending downward as a result of overfishing and poor recruitment in the Chesapeake.

With the striper fishery already under threat, it’s no wonder “the seal problem” has intensified the frustrations of many anglers. But, while we rail against the seals, how many of us know the story of how these marine mammals rebounded from their own brush with oblivion? The gray seal (Halichoerus grypus) and the harbor seal (Phoca vitulina) are the predominant species of seal found in Massachusetts waters. Both were extremely rare at the nadir of the striper fishery in the 1980s. It’s the gray seals—the bigger, horse-faced ones— that most frequently bedevil fishermen since harbor seals migrate north during the summer months. A male gray seal can measure up to 10 feet long and weigh well over 800 pounds.

Great White Shark Nauset Beach Attack

The booming seal population around the Cape and Islands has triggered an increase in the number of great white sharks in the area. One shark draws blood from its victim in five feet of water at the south end of Nauset Beach.

So many seals were bounty hunted (or “nuisance killed”) or were victims of bycatch by commercial fishers that by the mid-20th century, gray seals had been almost eliminated from U.S. waters. Some old-timers probably remember the days when someone could go into the town hall in Chatham and collect a $5 bounty per seal nose. They were called “seal buttons.” Despite this carnage, gray seals maintained a breeding population in Canadian waters, while just a few hundred harbor seals survived off the coast of Maine.

Massachusetts passed legislation to protect seals in 1965, but the big game-changer was the passage of the Marine Mammals Protection Act of 1972. According to the National Resources Defense Council (NRDC), the Act recognized that human activities were threatening marine mammals following “public outrage over the hundreds of thousands of dolphins killed in pursuit of tuna and the slaughter of baby seals for their fur.” The Act outlawed “hunting, killing, capture, and/or harassment of marine mammals” and placed a moratorium on import, export, and sale of any marine mammal or product derived from it. The blanket protection provided by this legislation is singularly responsible for the comeback of seals in Massachusetts waters, not to mention the protection and recovery of many whale and dolphin species, polar bears, walruses, sea otters, and manatees.

The research of marine biologist Stephanie Wood of the University of Massachusetts Boston confirms that the first gray seals to recolonize Massachusetts waters traveled south from the large breeding colony on Sable Island off the coast of Nova Scotia in the early 1990s. By the early 2000s, there was a growing pupping colony on Muskeget Island just west of Nantucket. That colony has continued to grow, while three other colonies have been established on Monomoy, Nomans Land, and Great Point on Nantucket. It’s difficult to estimate the population of gray seals in Massachusetts waters because of their peripatetic nature, but Jerry Moxley of the Duke University Marine Lab did an analysis of Google Earth images of Cape Cod in 2017 and concluded that the gray seal population on the Cape alone was between 30,000 and 50,000 seals.

Gray Seal

Gray seals (Halichoerus grypus) are the predominant species of seal found in Massachusetts waters during the summer months. This mature female (cow) on the left and male (bull) were photographed in the waters off Cape Cod. Male gray seals can exceed 10 feet in length and weigh over 800 pounds, while females are significantly smaller. Life expectancy is 25 – 35 years.

What Do Seals Eat?

Marine biologist Kristen Ampela’s 2009 Ph.D. thesis on the diet and foraging of grays seals is frequently cited in literature. Through scat analysis and necroscopies performed on the stomach contents of bycaught seals from commercial fishermen, Dr. Ampela concluded that 53 percent of the gray seal diet consists of sand lance (sand eel) and 29 percent from flounder, hake, and cod. Stripers barely showed up as a blip in her study, but that doesn’t mean seals won’t eat stripers. They are opportunistic predators and individual seals can show a great deal of variation from one another in their food choices. Dr. Ampela also acknowledges a problem with the data collection: a seal may kill a striper with a “belly bite,” but the striper’s bones won’t necessarily show up in a scat or stomach analysis.

Marjorie Lyssikatos, a NOAA research fishery biologist at the Northeast Fisheries Science Center in Woods Hole, is currently studying seal diet, and her findings are generally in line with Dr. Ampela’s. While there is no evidence seals are targeting striped bass, she said that doesn’t mean they’ll turn down a meal, especially one served up to them by a fisherman with a thrashing striper on the line. That’s learned behavior. However, she doesn’t believe the consumption of striped bass by seals is a meaningful factor in the health of the biomass compared to poor recruitment and overfishing.

Blair Perkins has lived on Nantucket since 1963 and fished there his whole life. Since 1999, he’s run Shearwater Excursions, an eco-tourism business that offers a variety of cruises, including seal tours. “Seals may be pretty good at taking a striper off a hook and line,” he said, “but I’ve scuba-dived with the seals off Muskeget in the summertime and have seen them interacting with stripers. My observation is that the seals just aren’t fast or maneuverable enough to catch those fish.”

Striper Seal Cape Cod Canal - John Doble

A gray seal snatches a striped bass off a fisherman’s line in the Cape Cod Canal. Encounters with seals shadowing anglers have become more common in recent years.

So, maybe seals don’t eat that many stripers, but what’s eating the seals (cue music from Jaws). There is a direct correlation between the increasing abundance of seals on the Cape and Islands and the growing presence of great white sharks. Greg Skomal, senior fisheries scientist at the Massachusetts Division of Marine Fisheries (DMF) in New Bedford, has been studying sharks for over 35 years and heads up the Massachusetts Shark Research Program. The first reports of white sharks near the Cape began in the mid-2000s. “Seals were starting to be everywhere, and as fishermen began to take notice, so did the sharks. We were getting more reports each summer of dead seals on the beach with wounds that could only be attributed to white sharks. In 2009, I got a call from a spotter pilot who saw white sharks off the Outer Cape. It’s been a pretty steady increase since then.” Dr. Skomal oversees a program that captures sharks and tags them with accelerometers that detect their every movement. The program has tagged 238 white sharks to date, including 50 in 2019 alone.

Buddy Vanderhoop welcomes the arrival of the sharks. “When the great whites come through, you won’t see a seal for a couple of days. Lately, we’ve been seeing a lot of great whites and makos off Gay Head and the Elizabeth Islands.” It’s no wonder the seals welcome the safety of the beaches.

But, are the sharks putting a dent in the seal population? Probably not much of one. The biggest causes of seal mortality are diseases like distemper and gear entanglement from commercial fishing, especially gill-net fishermen who catch thousands of seals in their nets each year. They also catch and discard stripers as bycatch. Diogo Godoi, who runs Gorilla Tactics Sportfishing out of Brewster, told me, “I’ve seen pair trawlers gill-netting for herring off the backside of the Cape with miles of dead stripers coming off those boats.”

Gray Seals Chatham Harbor

Gray seals in Chatham Harbor. Note the monofilament line encircling the neck of the seal in the center of the photo. Gear entanglement, especially from commercial gill net fishing, is a major cause of seal mortality. The two seals with green flipper tags are part of an ongoing study into the health, diet, movements, and genetics of the seal population by NOAA’s Northeast Fisheries Science Center.

Pushing Stripers to Deeper Water

Seals don’t necessarily need to eat a lot of striped bass to have a major impact on the fishery. Kristen Ampela explained to me that a concept called “the ecology of fear” is gaining the attention of wildlife biologists. “It’s the presence of a predator—even just the smell—that will change the way the preyed-upon species behaves. In the case of stripers, there are plenty of reasons to avoid seals”… just as there are plenty of reasons for seals to avoid sharks.

Where do we see the most seals? Close to shore or on the beach. According to the charter captains I interviewed, there is general agreement that surfcasting for stripers has gone to pot in the last five or six years. No mystery there. “All the things that striped bass used to feed on close to shore—sand lances, baby fluke and flounder, sea robins—are being eaten by seals,” Matt Perachio told me. “So, there’s not much of a point for the stripers to even come into shore anymore. There’s still a huge biomass of stripers, but now it’s way offshore because the bait is out there.”

Gray Seal

This gray seal has become a regular at the Chatham Fish Pier, where it begs like a dog for scraps from local anglers.

“I feel like the sand eel population is a fraction of what it was when I started fishing the Cape,” Diogo Godoi told me. “I’m seeing schools of bass 20 to 30 miles offshore while I’m tuna fishing. It’s as if they’ve become oceanic. And, what are they doing out there? Finding the bait.”

A New Normal

The “seal problem” is an unintended consequence of the Marine Mammals Protection Act, which did incalculable good for some 125 species of marine mammals. No one is complaining that we now have too many whales or manatees. Kristen Ampela pointed out that the problem developed because both animals—stripers and seals—have been managed and now there’s frustration with the way one affects the other. “But, it’s all a function of how humans have managed wildlife.” As the seal population grows, the mammals have become habituated to the routines of striper fishermen. It’s a fact of life and unlikely to change, which means fishermen have had to adjust. It might seem trite to say it, but isn’t making adjustments the essence of fishing?

I think we need to take the long view here. There’s never been a “normal” where striper fishing is concerned. The fishery has been in a constant state of flux forever. The ASMFC only declared the fishery “recovered” in 1995. Recreational landings have been on a downward trend for a decade and recruitment levels in the Chesapeake have been alarmingly low three out of the last five years. We can’t hang those problems on the seals. As Mike Bosley put it, “In the last 10 years, I’ve seen absolutely atrocious predation of stripers, but it’s all been by people in boats.”

The post Cape Cod’s Seal Problem appeared first on On The Water.


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