Shellfish bed closures raise climate change questions

In the wake of five reported illnesses, the state agriculture department has shut 22 shellfish beds in Norwalk and Westport and instituted a so far voluntary recall of oysters and clams harvested since July 3.

The culprit is Vibrio parahaemolyticus, naturally occurring bacteria that is generally seen more on the west coast. It does, however, thrive in warmer water, and the underlying question is whether water temperatures this summer are responsible for the outbreak and if they are, whether climate change is poised to make things worse.

“It’s a question that needs to be looked at,” said Kristin Derosia-Banick, an environmental analyst with the department’s bureau of aquaculture. “We just don’t know.”

Last summer, when water temperatures ran warmer than usual due to the unseasonably warm winter before, there was one reported case of Vibrio parahaemolyticus in Connecticut, though an outbreak (more than one case) occurred in Oyster Bay on Long Island’s north shore.

The bacteria is in the same family as cholera, causing diarrhea, stomach cramps, nausea, vomiting, headache, fever, and chills that are usually non life-threatening except in those with compromised immune systems.

It is found in raw and undercooked shellfish. Thorough cooking should destroy it. Of the five illnesses, all came from oysters. Even so, hard clams are included in the recall and closure. One illness was in a recreational shellfisherman. The other four involved four different restaurants.

The closed area is small, but Derosia-Banick said it’s “the heart of our shellfish industry — at least a million oysters a day are coming out of this area.”  She called it “a huge hit.”

The closure involves five companies, including the largest ones in the state. Shellfishermen contacted said they were still assessing the impact since the closed beds are largely transplant beds and they are in shallower water. Shellfishermen still have deeper water beds they can use.

The department has already ordered equipment to help them more thoroughly monitor shellfish, but as for any link to long-term climate changes, Derosia-Banick said her department couldn’t say at this point. “The opportunity for research is here.”

 

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