Edgartown’s bustling aquaculture industry is on hold this week, with Katama Bay oyster farms temporarily closed because of reported cases of Vibrio parahaemolyticus (Vp). The state Department of Public Health and Division of Marine Fisheries announced the closure, which is expected to last one week, on Wednesday.
The precautionary closure is the first in Massachusetts this year. A press release by the DPH and DMF attributed the closure to environmental conditions conducive to the growth of Vibrio parahaemolyticus in oysters harvested from the area.
Edgartown shellfish constable Paul Bagnall said Vibrio guidelines call for a closure when there are four or more illnesses tied to the oyster growing area in a 30-day period. The Katama Bay closure came after there were four illnesses reported in a 35-day period, Mr. Bagnall said. Because it takes time for illness reports to be investigated and confirmed, the state decided on a precautionary closure, he said.
There are 12 independent oyster farms operating on Katama Bay.
Mr. Bagnall said the closure began at dawn on Wednesday and the oyster farms will be reopened at dawn on Thursday, Sept. 11. Vp is a bacterial pathogen that naturally occurs in warmer waters. It can cause gastrointestinal illness, often including abdominal cramping, nausea, vomiting, fever and chills. Severe disease is rare and occurs more commonly in people with weakened immune systems.
People can become ill after eating raw oysters with high levels of Vibrio; cooking the oysters kills the bacteria.
Mr. Bagnall said the current water temperature in Katama Bay is 72 degrees. While the waters usually start to cool this time of year, a cool summer and warm September weather have resulted in water that is warmer today than it was three weeks ago.
“Current water temperatures in Katama Bay are consistent with water temperatures and environmental conditions that were associated with Vibrio illnesses in 2013,” a state press release about the closure said.
Mr. Bagnall added that it takes awhile to gather confirmed Vibrio reports. The time frame can be two to three weeks from the time someone becomes ill in Massachusetts; if someone gets sick out of state, it can take as long as eight weeks.
He said a one-week closure would cost oyster farmers between $500 and $2,000, depending on the grower. He also added that while there are 12 oyster farms on the bay, the closure affects more than that, with most farms employing helpers. A silver lining, he added, is that this closure does not include a recall of oysters already harvested and shipped.
The idea of closing the oyster fishery in warm months, though, is not new. Katama oyster farms were closed last September for about a month because of Vibrio cases. Oyster farms on Cape Cod and in Connecticut were also closed.
State officials say Vibrio has been on the rise over the last several years. Thirteen people were sickened in 2011, and the number increased to 58 in 2013. Health officials have attributed the increase to warming waters and the increased popularity of eating raw oysters, among other things.
This year, the state instituted new protocols to prevent Vibrio, and extended closures.
Earlier in the summer the state confirmed isolated cases of Vibrio, but said they had not been tracked to any mishandling. Oyster farmers were adhering strictly to the new protocols, state officials said.
Mr. Bagnall said that while the closure is not good news to Katama oyster farmers, “they are taking it in stride.”