April 23, 2010
The Texas Department of State Health Services has temporarily closed most
Texas coastal waters to the harvesting of oysters, clams and mussels because of
an algal bloom and the potential presence of toxins in some shellfish.
The affected area extends along the Texas coast from Galveston to Port
Aransas. Commercial and recreational harvesters should not harvest oysters,
clams or mussels from the closed areas.
The closures come after DSHS crews found elevated levels of the Dinophysis
organism entering the Texas bays from offshore waters, indicating a bloom is
occurring where Texas oysters are harvested. A bloom can occur when microscopic
algae grow quickly in water, forming visible patches. DSHS officials say they
know of no health issues associated with people being in water containing the
The toxin produced by Dinophysis, okadaic acid, can accumulate rapidly in
shellfish tissue and cause diarrheic shellfish poisoning, or DSP, in people who
consume oysters, clams or mussels. DSP symptoms include vomiting, diarrhea,
nausea and cramping. DSP is not life threatening and does not generally cause
long-term effects. DSHS is not aware of any illnesses associated with this
Texas shellfish harvested before today’s closure do not pose an elevated
health risk. Cooking does not destroy the toxin. The toxin does not affect other
seafood, such as shrimp and crab.
“Temporarily closing the waters to harvesters is a preventive but necessary
measure,” said Kirk Wiles, manager of the DSHS Seafood and Aquatic Life Group.
“Historically, this organism has produced toxin in Texas oysters that can cause
illness if the oysters are consumed.”
In 2008, a bloom of Dinophysis produced toxin in oysters and required DSHS to
close several bays on the middle Texas coast.
DSHS will continue to monitor the movement of the organism. Oyster tissue
will be tested to determine when safe harvesting can resume. The area will
remain closed to harvesting until further notice from DSHS.
Dinophysis occurs naturally in ocean waters and estuaries. Typically it is
not found in high numbers along the Texas Gulf Coast.
The public oyster season ends April 30 in Texas. If no closure is in effect,
oyster harvesting is allowed year round on private oyster leases in Galveston
Bay. Harvesters should check the status of harvest areas by calling DSHS at
(News Media Contact: Carrie Williams, DSHS Acting Press
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