Katama Bay oyster farms reopened for business last Saturday, about three and a half weeks after the area was closed to harvesting because it was linked to cases of Vibrio bacteria.

The Massachusetts Department of Public Health and the Massachusetts Department of Fish and Game, Division of Marine Fisheries (DMF) announced the reopening Friday afternoon, Oct. 4. The 12 independent oyster farms operating on Katama Bay were back to business Saturday at dawn.

On Sept. 9, the state announced the bay would be closed to oyster harvesting after two cases of Vibrio parahaemolyticus (Vp) were tied to the area.

Vibrio is a naturally occurring bacterial pathogen that is more prevalent in oysters in warmer water. People can become ill after eating raw oysters with high levels of Vibrio; cooking the oysters kills the bacteria.

Vp can cause gastrointestinal illness, often with abdominal cramping, nausea, vomiting, fever and chills. There are rare cases of severe disease, most commonly for those with weakened immune systems.

According to a press release from the DPH and DMF, state officials decided to reopen Katama Bay because no new human cases of Vibrio have been reported since the closure and weekly average water temperatures have declined since the implicated oysters were harvested.

Because cases of Vp are on the rise in New England, the state instituted a Vibrio control plan earlier this year. That plan mandated a closure if two or more cases of sickness were tied to the area. The criteria for reopening are no new reported illnesses for two weeks, declining water temperatures and tests of oysters in the affected area that come back clean.

Oyster beds in Duxbury, Kingston, Marshfield and Plymouth were also reopened on Saturday; those areas were closed on August 30 because of Vibrio.

According to the DPH, there have been 50 reports of confirmed Vp in state residents since May 31, 2013, with 31 of those cases linked to consumption of raw oysters from Massachusetts growing areas. In the same time period last year, the state said, there were 27 cases. Vibrio has led to oyster bed closures in several other states, including Connecticut, New Jersey and New York.

Edgartown shellfish constable Paul Bagnall said the announcement was

good news, and surprising as it came earlier than expected. Samples from Katama Bay oysters were being sent for testing every Monday, Mr. Bagnall said, and he hadn’t heard results. Mr. Bagnall said it was his understanding that the decision to reopen was primarily based on cooler water temperatures.

The reopening was welcome news to the oyster farmers on the bay, and to those who like to eat Katama oysters. Mr. Bagnall said the first oysters were headed to markets by Saturday afternoon. About five million oysters are harvested from Katama Bay in a year, according to Mr. Bagnall.

The oyster farmers might have lost some sales, he said, noting there are only so many weeks in a year. “I think a little bit of lost income,” he said.

And because oysters were not sold for more than three weeks, some of the oyster cages were crowded as the oysters continued to grow and none were removed. He said to his knowledge, the oysters did not grow to be so big they could not be sold.

“It didn’t seem to affect the demand,” he added.

The bay was reopened before Columbus Day, as he’d hoped, Mr. Bagnall said, adding that the months before Christmas are a busy time for oysters, and Katama oysters can now be served in Kenmore Square during the Red Sox playoffs.

“We appreciate the cooperation and understanding of the public and the industry,” said Massachusetts Public Health Commissioner Cheryl Bartlett in the press release announcing the reopening. “It was important to monitor environmental conditions and reports of illness, which gave us confidence that public health concerns were addressed before the harvesting areas were re-opened.”

“Our Division of Marine Fisheries is committed to working closely with our state public health partners, federal officials and the industry to enhance the Vibrio control plans currently in place,” said Department of Fish and Game commissioner Mary Griffin.

Going forward, Mr. Bagnall said, closing the bay when it hits peak water temperatures could be a possibility. He said the oyster farmers are willing “to go above and beyond what the state requires,” a possibility that was discussed by several farmers at a shellfish committee meeting earlier this month. One idea is to put the oysters on ice right when they come out of the water.

“Jack and I are thrilled to be harvesting oysters again,” said Sue Blake, who operates Sweet Neck farm with her husband, Jack, in an email. “We are happy for all the farmers.”

She said it is business as usual and “the oysters look beautiful and taste delicious.”

“Fall is a busy time for oysters farmers,” Mrs. Blake added. “There is a lot to take care of before the cold winter winds begin to blow.”