Bay Scallop Die-off related to Climate Change?

Publication: The Southampton Press By Michael Wright   Nov 5, 2019 10:25 AM

Nov 5, 2019 4:59 PM

Dead Bay Scallop

A massive and mysterious die-off of bay scallops over the past summer wiped out as much of 95 percent of the valuable and iconic shellfish in parts of the Peconic Bay system, raising concerns about the effect that climate change may have on the future of the East End’s most famous natural resource.

The scale of the losses, the scientists who have documented the destruction said, is so great in some areas as to be reminiscent of the devastation wreaked by some of the infamous “brown tide” algae blooms of the late 1980s and early 1990s, which decimated the wild stock and all but ended a centuries-old commercial fishing industry that relied solely on harvests from the East End’s bays.

The cause of this year’s devastation is not immediately clear, but scientists say that the arch-enemy of bay scallops — algae blooms like brown tide and the more recent “rust tide” — do not appear to be at fault, and other likely culprits also do not seem to be to blame.

What’s left to blame, according to one of researchers who has tracked the die-off, is a confluence of environmental conditions and the stresses of the scallops’ own biological cycles that may have killed the shellfish, even as they sowed the seeds of next year’s stock.

There is some good news amid the devastation, primarily because half the reason that the scale of the die-off is remarkable is that there were so many live scallops to start with — and they appear to have spawned before they died, leaving huge numbers of their offspring in their place.

Population Takes A Nose Dive
Surveys conducted by Cornell Cooperative Extension biologists last spring had revealed that the annual “set” of young-of-the-year scallops was enormous and on track to support a commercial take rivaling or surpassing those of the robust hauls of the last two years.

But when the scientists donned wetsuits and returned to their underwater survey areas throughout the Peconics early last month, they found the ghostly signs of an epic massacre: thousands of scallops sitting where they died, their shells gaping open.

“We call them ‘cluckers,’” Dr. Stephen Tettelbach, who leads the surveying for Cornell, said of the dead scallops, whose twin shells have remained attached and sitting on the bay floor. “Based on the cluckers, it looks like the mortality happened a while ago — a few months, probably. The pattern was the same everywhere we went — there were no freshly dead adult scallops. They had no tissue left in them. So whatever happened to them happened a while ago.”

A longtime marine biology professor for Long Island University at Southampton College and C.W. Post College, Dr. Tettelbach has been conducting bi-annual surveys of scallop populations since LIU and Cornell began an effort to restore the scallop stocks depleted by the brown tides that beset the bays between 1986 and 1995. Through the Cornell hatchery in Southold, the initiative released more than 10 million seedling-sized scallops into the bay over the last two decades in the hope of restoring the spawning foundation for the species.

Looking For Answers
Since discovering this year’s die-off, Dr. Tettelbach and other scientists have been exploring what could have caused the mortality.

The destruction of harmful algae blooms was quickly ruled out, because there were none in the Peconics this year — the second straight year that the destructive successor to the brown tides, a red algae bloom that scientists have dubbed “rust tide,” has been absent from local bays, after a 15-year run of increasingly dense blooms.

Dr. Tettelbach himself had pinned a large die-off of scallops in the same area in 2012 on the dense blooms of rust tide that killed what had looked to be a robust stock just weeks before the harvest began.

The second thought about this year’s event — a disease of some sort — also is being seen as unlikely, because the die-off does not appear to have extended to juvenile scallops, which the survey divers saw alive and in great abundance.

And the vast extent of the mortality could not be chalked up to the usual cast of submarine characters that prey on scallops like crabs, whelks and some fish species.

But there was a wild card this year in the form of an invasion of a certain species of shellfish-eating stingrays that have wiped out oyster beds in the Chesapeake Bay.

Thousands of cownose rays, a brown-winged creature that feeds primarily on shellfish, swarmed into East End waters in July and August, roaming the bay bottoms in schools of dozens or hundreds.

Dr. Tettelbach said there were accounts of the rays being seen in Hallock Bay, in Orient, but he has not yet confirmed that they made their way deep into the Peconics. He said the rays could explain the disappearances in some of the areas where large number of scallops had been seen in the spring, and now there are no signs of them at all.

But the species would not be easy to blame for the full extent of scallop losses this summer, since there were so many intact shells left behind as a sign that the scallops simply died where they sat. The shells of scallops set upon by the rays would be crushed, he said.

A Matter Of Climate?
Eliminating those considerations turned the former professor’s critical thinking to other environmental factors, and the warm temperatures of the summer.

Data from water monitoring stations at the western end of the Peconics revealed that water temperatures hovered around 84 degrees for several weeks this summer — an unusually long stretch of exceptionally high temperatures, and near what is understood to be the lethal limit for scallops.

In a typical parallel, levels of dissolved oxygen in the water were also very low — near zero at times — which typically will result in the death of any marine species.

But those conditions have occurred before at various times of past summers, and broad die-offs of scallops were not seen.

Dr. Tettelbach said his hypothesis is that the high water temperatures and low dissolved oxygen levels had set in early enough this year as to coincide with the weeks of early- to mid-summer when scallops are going through their first spawning cycle — some will spawn again in the fall — which can weaken them and make them more sensitive to environmental conditions.

“What I’m thinking is that the stress from spawning combined with environmental stressors may have been the cause,” he said, noting that if his hypothesis is correct, it would exacerbate concerns about a trend of warming waters. “We’ve had water temperatures in the Peconics over 80 degrees the last five years. Years ago, we never saw that.”

Impacting Local Economy
Word of the scientific findings was not news to area baymen, some of whom routinely do their own pre-season surveying to keep tabs on their economic prospects for the fall.

Many didn’t even set out in their boats in search of scallops on Monday, the first day of the season in New York State waters.

“I went clamming today,” Edward Warner, a bayman from Hampton Bays, who is also a Southampton Town Trustee, said on Monday. “The only other time I can remember not going scalloping on the first day was, maybe, 1986, the first year we had the brown tide.”

Among those who did go, many found little return for their efforts.

“I had 14,” said Stuart Heath, a bayman from Montauk who scoured traditional scallop grounds in Shelter Island Sound. “I went all around North Haven, from Margarita guy’s house … to Sag Harbor, around the moorings, Barcelona, all around Northwest. Terrible. We’ve had a terrible year already — now this.”

Wainscott bayman Greg Verity said he ran his small boat across to the North Fork and found enough scallops to fill several bushel baskets, but he was still well short of the 10 bushels that a bayman is allowed to harvest each day.

East Hampton’s baymen said there’s only a faint glimmer of hope, when East Hampton waters open next week, that there may be some scallops lurking in areas that haven’t been prospected.

The Cornell scientists conduct their surveys in the string of bays connected to Great Peconic Bay, from Flanders Bay in the west to Orient Harbor in the east. They do not survey any of the waters off East Hampton — where scalloping is not allowed until this coming Sunday.

Pre-season scouting has not given East Hampton’s baymen much cause for hope, either.

Mr. Heath and Mr. Verity said they’d heard talk of scallops in Three Mile Harbor, where the town releases thousands of hatchery-raised baby scallops each year. But that supply is often depleted quite quickly, especially when the harvest in other areas is poor.

On Monday evening, Mr. Verity and Sara Miranda were counting themselves as lucky while they shucked their way through the briny pile of scallops on a steel table set up in a trailer next to Mr. Verity’s cottage in Wainscott.

“I’ll sell ’em to whoever wants ’em,” he said, as he flicked the glistening white morsels of meat into a pile.

The scene was not being replicated in many of the seafood shops around the region.

“So far, we’ve got nothing, not even one bushel,” said Danny Coronesi at Cor-J Seafood in Hampton Bays, one of the areas largest buyers.

“I’ve been here a long time. We’ve never had this. Even on bad years, opening day some guys would come in with them.” He added, “We had thought this was going to be a great year.”

Comment from Win With Wind: Scientists quoted think global warming is causing this die-off. Are scallops the canary in the coal mine for the marine environment and when will all local fishermen understand that global warming will destroy their industry, not offshore wind? 

1 thought on “Bay Scallop Die-off related to Climate Change?

  1. Pingback: Kemp’s Ridley Turtle | WIN WITH WIND

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