New Parasite Showing Up In Some Nantucket Bay Scallops

Nantucket fisherman John Logan calls them "Dalmatian" scallops.

At the start of the island's commercial bay scalloping season in November, Logan noticed something strange as he opened the shellfish in his shanty. Some of the scallops had small black spots on them.

"We called them Dalmatians because they're spotted," Logan told the Harbor & Shellfish Advisory Board late last month. "I've never seen this before. It's a new thing."

Logan's comments came in response to a question from the town's shellfish and aquatic resources manager Tara Riley, who asked the scallopers in attendance if they had seen the phenomenon during the ongoing commercial season.

Riley believes the black spots are a kidney parasite known as bay scallop marosporida, which researchers believe may have been the culprit in the decimation of the Peconic Bay scallop population on Long Island in 2019.

"I saw some scallops that came from Tuckernuck the other day that looked pretty awful," Riley told the advisory board. "The meats that someone sent me a picture of, you might see a couple spots, but this was all over. It's a parasite they've been documenting in Peconic, a kidney parasite, we haven't really seen it. We only see it in the second- or third-year scallops. They have samples from us, we send them every season from both harbors. I've only seen them in a few that we're opening from the dock."

Logan added that it was more prevalent early in the season, when his openers saw "a dozen or two" in the two-box limit they pulled from the harbor. Now, several months into the season, Logan is fishing in different areas and said the number of scallops he's seen affected by the parasite has decreased.

Scalloper Bob DeCosta has noticed the black-spotted scallops as well, but in very small numbers.

"If I open a six-box limit, I get one or two per limit," DeCosta said. "It’s not a lot. We throw them in the barrel...There has been some, but not a ton. But it's through the whole muscle, black specks."

Scalloper Jim Sjolund told the board the parasite has been noticed on Martha's Vineyard as well. Officials there have launched a unique study with Stony Brook University to better understand the potential impacts.

For now, it appears the infections on Nantucket are not widespread, and Riley said she may distribute some bags to the island's shanties and ask the openers to set them aside so she can freeze them to send for study. There is no concern, she said, about the parasite affecting humans who may happen to eat an infected scallop.

Riley emphasized that the collapse of the Peconic Bay scallop fishery was likely the result of a combination of factors - including high water temperatures in the summer and harmful algal blooms - along with the kidney parasite.

"It's a question of are we going to see more of it and what will it do to the scallops," Riley said.

"It's a new thing, and if it's starting to come up from Peconic, that fishery is gone now, so let’s get ahead of it and see what the cause is," Logan added.