Bay Scallop Researchers Explore the Fall Spawn

Pictured Above: Peconic Bay scallops spawned in the fall of 2022

For the past four seasons, scientists working to understand Peconic Bay scallops have found a clear correlation between the stress of scallops spawning in warming springtime waters with the death of nearly all of the adult scallops over the course of the summer.

But what would happen, researchers working on Cornell Cooperative Extension’s Peconic Bay Scallop Restoration Program wondered, if they worked to expand a smaller scallop spawn that happens in the fall?

This past year, the CCE team embarked on a new experiment, taking an existing brood stock of adult scallops to produce two new batches of scallops, one spawned in the spring, and one spawned in the fall.

Those scallops, currently in the hatchery at CCE’s Southold Marine Education and Learning Center at Cedar Beach, will be placed in three locations in the Peconic Estuary this coming spring. Each group will be monitored biweekly to see how well they fare with warming waters and two other factors believed to play a role in the die-off the past few years — low dissolved oxygen and a parasite that is active during warmer months.

“We’ll have a known number of scallops in each bag, and we’ll track their survival and their reproductive status,” said CCE Aquaculture Specialist Harrison Tobi, who is in charge of field work at the Marine Center. 

They will also be collecting samples for Stony Brook Marine Animal Pathologist Bassem Allam, who is studying parasite infections found in the dying scallops each of the past four years.

“Most of the exposure to the parasite is between June and October,” said Mr. Tobi. “The hypothesis is that the infection intensity might be lower in the fall-spawned scallops, and we might see better survival.”

“We’re constantly doing experiments, all the time. This is a proof of concept,” he said, adding that the Marine Center spawned just 30,000 of the fall scallops in two spawning sessions in October and November, compared with the 1 million scallops spawned there each spring, most of which are then placed in a spawner sanctuary in Orient Harbor before being seeded in the wild. 

This experiment was funded by the Robins Island Foundation, the Long Island affiliate of the Moore Charitable Foundation, which funds ecological projects.

“The Robins Island Foundation has supported the critical work of the scientists at the Cornell Cooperative Extension for nearly 30 years, including their successful Suffolk Project in Aquaculture Training that encourages community members to become stewards of their environment and to restore shellfish to the bays,” said Ann Colley of the Robins Island Foundation. “The health of the bay, including the scallop fishery, is a critical part of the East End, and we remain steadfast in our support of protecting this fragile and important ecosystem. We are hopeful that the new approach to spawning that CCE is currently deploying results in the Peconic Bay scallops thriving for generations to come, and we are encouraged by the early signs of success.”

“The bay scallop is one of several indicators of the impacts of climate change on overall ecosystem health,” she added. “We are seeing unprecedented changes in water temperatures that have affected many species including scallops and eelgrass. Based on these changes, it is important for us to support projects like this that develop proactive and innovative responses that address the problem.”

As the same pattern of scallop die-offs has persisted each of the past summer seasons, researchers have become more convinced that their original hypothesis — that warm water and low dissolved oxygen at the time of the spring spawn, in addition to a parasitic infection, had stressed adult scallops to the point where they don’t survive until they can be harvested in the fall.

These three factors have been called “a perfect storm” in the destruction of the scallop industry by Stony Brook shellfish researcher Dr. Emmanuelle Pales Espinosa.

Warming temperatures in the bays, driven by climate change, are out of the hands of people working to restore the fishery, but other factors may be within our ability to change.

For the Peconic Bay Scallop Restoration Program, this fight is an existential one — for the past 18 years, under the direction of shellfish ecologist Stephen Tettelbach, the program has been working to bring the scallop population back from the brink of collapse. The program had nearly succeeded in doing so before the die-offs began, with bay scallop landings in the Peconic Estuary exceeding 108,000 pounds, with a dockside value of $1.6 million, in 2017 and 2018, just before the die-offs began in 2019. The fishery was declared a federal disaster in 2021, making scallopers and related industries eligible for federal disaster assistance.

Dr. Tettelbach retired in 2022, and Mr. Tobi, who came to the Marine Center in 2021 from Cape Cod, where he’d most recently worked in commercial aquaculture, is now tasked with filling his shoes.

“This was the most successful scallop restoration program in the country,” said Mr. Tobi. “They brought it back from the brink of collapse for 15 years. Steve was an idol of mine. Even before we met, I was referencing his research.”

The species of scallop that grows in the Peconic Estuary, Argopecten irradians irradians, the northern bay scallop, lives just two years, and with its thin shell and Goldilocks sensitivity, it is famously difficult to grow in a hatchery. These scallops can only be harvested in the wild during their second year of life, after they display a prominent annual growth ring on their shells. 

In the past four seasons, there has been some hope for recovery, because despite the near-total die-off of adult scallops, many had been able to spawn before they died, allowing their genetic material to continue, if only just till the following spring.

The same species of scallop that grows in the Peconic Estuary also grows in the cooler waters off Cape Cod, where researchers are partnering with many of the Long Island scientists working to understand the relationship between warming temperatures and other factors affecting the scallops.

But these scallops can’t be moved between New York and Massachusetts without being cleared as parasite-free, said Mr. Tobi, and importing another species entirely is well beyond the scope of research that can be ethically considered. This is Argopecten irradians irradians’ home.

In addition to the fall-spawned scallop experiment, the Marine Center is also working to cultivate Peconic Bay scallops that have survived the die-offs, in the hopes of supporting strains of scallop that are genetically more resilient in the face of rising water temperatures. 

Last fall, Mr. Tobi said, it took his field team five days of diving to collect just 60 living scallops to use for brood stock for that project.

One of the emerging issues with unseasonably high water temperature is what it does to scallop metabolism — the animal senses the water is warming and becomes more active, but there is not enough algae in the water during the warm snaps to meet the scallops’ heightened metabolic demands. They respond by using their own gonads as a food source, further depleting their ability to perpetuate the species.

It’s Marine Center Hatchery Manager Josh Perry’s job to make sure the adult scallops used to breed the new generations for the experiment are ‘conditioned’ by feeding them enough algae to promote a robust spawn. Then, those baby scallops need enough algae to make it through to the following year.

“In times of turmoil, they reabsorb their fat and gonads, so we create an optimal environment for feeding, and end up with nice, robust and beautiful scallops,” said Mr. Perry as he checked on the status of tanks of algae and a hatchery filled with baby scallops, oysters, clams and ribbed mussels. It was a warm late-February morning, and the air temperature was climbing to the high 60s. 

Within a couple weeks, the scallops in the hatchery would be moved into a grow-out area in a nursery in Cedar Beach Creek, in anticipation of being moved out into the field in early May.

The next step in the fall scallop experiment will involve placing two sets of protected bags of scallops — one spawned this past spring and one from the fall, both with the same parents — in three locations. One is in Northwest Harbor in East Hampton, where water temperature and dissolved oxygen seem to be ideal for scallops, and the other two are in two sites in Orient Harbor, one along the open waters along the Orient causeway and the other in the spawner sanctuary, farther east along the causeway.

“Scallops are super finicky and hard and expensive to grow,” said Mr. Tobi, who expects to be out in the field all spring, summer and fall diving to document the progress of the Marine Center’s experiments. “But the image of the scallop is everywhere here. To bring that back is very important for the region.”  —BHY