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September 17, 2004

Marine Advisory Program response to oyster vibrio outbreak

Temperature sensors installed to give early warning

Prince William Sound—Marine Advisory Program (MAP) aquaculture specialist Ray RaLonde and Cordova MAP agent Torie Baker recently toured oyster farms in Prince William Sound with Alan Austerman, fisheries advisor to Alaska Governor Frank Murkowski.

The tour occurred on the heels of an outbreak of the marine bacteria, Vibrio parahaemolyticus, in Prince William Sound. In late July, Alaska health inspectors traced several cases of the non-lethal illness in people to raw Alaska oysters they had eaten that were contaminated with the bacterium. Following the outbreak, the state temporarily banned the sale of oysters from the sound.

RaLonde, who has spent his career helping Alaska build its shellfish mariculture industry, arrived in the sound with ocean temperature sensors to install at shellfish aquaculture farms to provide an early warning system for shellfish growers.

"This particular bacteria becomes a potential problem when ocean temperatures rise," said RaLonde. "These sensors will tell us when there's a spike in water temperature at the farm itself. They can give us an early signal that we should be concerned."

RaLonde said the vibrio bacterium is likely ever present in the seabed. Alaska has not had to deal with it before because the state's waters are generally quite cold. But ocean temperatures in the Sound lately have been very warm, at times reaching 63 degrees in places. This has created the conditions the bacterium needs to multiply rapidly and pose a problem for oyster growers.

"One of the things I want to do while I'm out here is to educate growers about vibrio," said RaLonde. "There are strategies for dealing with the bacteria."

In many parts of coastal Alaska, shellfish mariculture remains a small, but growing industry. In 2003, there were 56 shellfish farms occupying 220 acres of state tidelands in Kachemak Bay, southeast Alaska and Prince William Sound. These farms produced primarily oysters but also clams and mussels worth $520,000. Numbers for 2004 are not available but are expected to be higher because of new farms being established in Southeast Alaska.

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