Three-month-old scallops are displayed in Southold on Oct. 31, 2020.

Three-month-old scallops are displayed in Southold on Oct. 31, 2020. Credit: Randee Daddona

Weeks after Stony Brook University researchers reported warming trends have heightened the recent die-offs of Peconic Bay scallops, biologists at Cornell say they’re experimenting with a change in the spawning season to breed the mollusks when water temperatures are cooler.

The work by the Cornell Cooperative Extension’s Marine Program seeks to reduce stress factors thought to be prime factors in the scallops' decline — warming waters that can result in lower oxygen levels during the high-stress summer spawning season.

Researchers at Cornell’s hatchery in Southold say they’ve conducted two successful spawns of about 30,000 bay scallops in October and November of 2022, in the first shift away from a typical summer spawn. They now plan to conduct field tests to see if the fall spawners have better survival rates and higher reproduction with better resistance to pathogens.

“If the fall-spawned bay scallops survive better than those produced in summer, such findings could prove highly useful in future restoration efforts,” Cornell said in a statement Thursday. The work is funded by The Robins Island Foundation.

Cornell’s scallop program specialist Harrison Tobi called the fall-spawned scallops “promising” but cautioned, “We need to see if these scallops will survive better than those we produced in summer."

Tobi said the biologists at the hatchery manipulate the spawning cycle by gradually increasing the temperature and food availability of the adult scallops to “trigger them to ripen,” over a five-week period. They are then dropped in warmer water to trigger spawning.

In the case of the new fall-spawning scallops, this would happen in September rather than the typical May. The September-spawned scallops would then get “planted” in spawner sanctuaries in November for the next growth phase.

Doing so, Tobi said, could reduce the scallops’ exposure to a known parasite that thrives in warmer waters by four months. The hope is that “they’d survive better until harvest in the second fall.”

With positive results from the pilot and additional funding, Tobi said, the facility could eventually spawn hundreds of thousands of scallops in this way.

The next step, he said, is “getting in the water and working with my team in the months to come to learn if what we’re trying will significantly improve scallop survival. I’m confident that we’ll soon be better equipped to restore the fishery back to what it was before the recent die-offs.”

Researchers have been examining a range of potential factors in the Peconic Bay scallop die-offs for the past four years, including parasites, algal blooms and predators. But the consistent trend through that time has been higher water temperatures and a corresponding reduction in oxygen levels.

A paper last month by Stony Brook University professors in the journal Global Change Biology found that “extreme summer temperatures, becoming more frequent under climate change, exacerbate the vulnerability of bay scallops to environmental stress and have played a role in the recurrent population crashes."

“The last three or four summers have been warmer than in the past, particularly around the time the scallops are spawning,” one of the authors, Christopher Gobler, told Newsday.

“This is a climate change issue and the climate is going to continue to change,” said Gobler, a professor at SBU’s School of Marine and Atmospheric Sciences. “Sometimes people may hear the term and it’s hard for them to grasp. But this [scallop die-off] is one of the things that brings home what it means to be living in a warming world.”

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