Over the past five-plus years, Peconic Bay scallops have suffered mass die-offs blamed on an infectious parasite, but researchers at the Cornell Cooperate Extension have found a source of scientifically informed hope: genetic diversity.
Harrison Tobi, an aquaculture educator with the extension’s Bay Scallop Restoration Program, put it plainly for nonscientists: “Basically, they’re inbred in the Peconic.”
To understand the findings, Mr. Tobi discussed when the parasite was first identified in Argopecten irradians, or Peconic Bay scallops, in 2019: The “fishery collapsed by almost 99 percent,” resulting in losses of over $1 million annually since then.
“First off, it’s what we call a novel parasite, which means it was literally never discovered before,” Mr. Tobi said at the Southold laboratory. “Its genetics are brand-new to the scientific world.”
After the collapse, the Cornell Cooperative laboratory sent samples to Stony Brook University’s marine animal disease laboratory, led by Bassem Allam. “That is when we first discovered the parasite,” Mr. Tobi said.
There is no way to know how long it might have been present. “It’s like Schrodinger’s cat: We can’t really say it was or it wasn’t there because we didn’t test for it,” he said. Most likely, it had been present for some time, as it was also found in Maine, Massachusetts, and New Jersey.
The laboratory began to test and hypothesize. The parasite “continually showed up, and it was/is most prevalent in the summer months,” when the water temperature is at its warmest, Mr. Tobi said.
When the water cools down in the fall, the “intensity,” or prevalence, decreases. With these hypotheses, the laboratory began to look at approaches to curb or alleviate the effects of the disease.
First, it looked for a subpopulation of northeastern scallops that “exhibit disease resistance.” Hypothetically, a scallop could resist the disease, giving it lower levels of infection.
“We did not find that,” Mr. Tobi continued. “What we found was tolerance.” Essentially, all the subpopulations had the same level of infection intensity, the scientists found, but some groups had higher survival rates at that intensity.
Mr. Tobi said to think about tolerance levels like the flu, though he acknowledged that it isn’t a perfect analogy. When a 20-year-old person gets the flu, they will likely be fine. However, when an 80-year-old person is infected, the symptoms can be far worse.
With that, two separate ideas emerged. The first has to do with genetic diversity within the local scallop population. Looking at samples from Peconic Bay over the past five years — when the parasite was first identified — the scientists found that genetic diversity decreased throughout the population. That is, they became more inbred.
“That loss of genetic diversity likely resulted in a weaker bay scallop population, and we now believe that that loss, in conjunction with the parasite, is what’s driving the die-offs in the Peconic,” Mr. Tobi said.
Separately, John Barley Dunne, the director of the East Hampton Town Shellfish Hatchery, found his own reason for optimism: several adult scallops at Three Mile Harbor, Napeague Harbor, and Lake Montauk.
“I was surprised when I jumped in the water, started swimming around, and saw so many large scallops in one area,” which probably spawned from his hatchery’s nurseries, he said. Over all, though, scallop season looks “pretty dismal all around.”
Mr. Dunne took the mature scallops to Dr. Allam at Stony Brook University for genetic testing. The results have not yet been returned, but the data will likely provide insight into whether there is some genetic mingling from other populations, such as Moriches Bay or Martha’s Vineyard.
The Cornell Cooperative Extension scientists also looked toward Martha’s Vineyard, sending groups of scallops north for testing. They found that Peconic Bay scallops fare just as poorly there. The inverse, however, was also true: Martha’s Vineyard scallops do just as well in their own bays as they do in the Peconics.
More locally, though, the Bay Scallop Restoration Team looked at scallops from Moriches Bay for answers. The harvest population there has grown dramatically in recent years.
Two years ago, some 1,000 pounds of scallops were reported harvested to the New York State Department of Environmental Conservation. Last year, that number was around 5,000 pounds. On the other hand, only around 6,000 pounds were reported harvested in Peconic Bay, which is “really bad, really bad,” Mr. Tobi said.
Right now, the Cornell Cooperative Extension does not have data on parasitic infection in Moriches Bay scallops. However, it is likely that they are being infected as well, despite the rise in population there.
The idea then is to inject a population of Moriches Bay scallops — 300 total — into the Peconic Bay population to increase genetic diversity and create a stronger, healthier bay scallop that can tolerate the parasite. Again, to put it non-scientifically: “The Moriches ones likely are not as inbred.”
Hopefully, Mr. Tobi said, “when they spawn next year, they can pass those genetics of tolerance to the parasite down to their offspring. Then, within the next couple years, similar to when the program was initially started, we’ll start to see an increase in survival until harvest season.”
The goal is not to get the scallops to survive as a species; however, because that isn’t a concern: “They’re not going to disappear. They just disappeared as an economically viable resource,” Mr. Tobi said.
Working with researchers from other institutions, the D.E.C., and local fish markets, the Bay Scallop Restoration team is working to bring them back as that resource.
“Baymen — talk about a hard job,” Mr. Tobi said. “It’s a really hard job. So, if we’re able to bring back, even if it’s 10 grand a year for however many baymen it is that are able to get out there: That’s Christmas, that’s repairs for their boat.”
While change won’t be immediate — “from what I’ve heard, this year’s not good” — it is hoped the Moriches Bay scallop supplement can create a blueprint for the future.
“Hopefully over time — spawn after spawn after spawn, in the wild — that will become the dominant genotype. So, basically the Moriches genotype will be dominant in the Peconic, and we’ll see similar resiliency on a population scale, and hopefully increase commercial harvests over time.”
The other working hypothesis concerns the relationship between water temperature and parasitic intensity. Recently, Mr. Tobi collected five adult scallops from their field site in Northwest Harbor, “which is hopeful.”
Those scallops were planted in the fall, after the infection intensity had passed its summer peak. By the spring, they had “no trace” of infection.
“If you’re born in September, you’ve likely missed the high intensity of the parasite in your first year,” he said. “So, the scallops I found in Northwest Harbor were almost all fall-spawn adult scallops.” As for the data’s usefulness, “It just reinforces some of our other projects.”
The alternative — supplementing scallops from Moriches Bay for greater genetic diversity — is preferable, he said, because “if we can use that instead of altering the hatchery schedule, that would be way better. That’s why I think the genetic route is the way to go. It’s already been done, and it keeps everything as it was, to a degree.”
Mr. Dunne separately urged long-term optimism in the future of scallop harvests.
“I think it’s important to remain hopeful,” he said. “I’m very hopeful with what I saw recently: that there were so many adult scallops still surviving and looking healthy right before harvest season here in town waters.”
Genetic testing has evolved a lot over just the past couple of years, Mr. Tobi said, which has helped the researchers identify and combat the problem. Scientifically, however, he identified a difference between preventing and fixing.
“If you keep using the same stock, we’re doing the same thing that potentially led us to where we are now, which is that loss of diversity. So, you’ve just got to continually supplement new populations in. It’s called stock enhancement,” he said. “Because we’re humans, we typically go after something once the problem has arisen, but a lot of times people will do this to prevent it.”
Right now, the laboratory is in “fixing mode.” In the future, however, he wants to shift it into “preventative mode, which is continuously making sure we have new genetics coming in and we’re not inbreeding.”
