Warm weather and low tides are good for harvesting shellfish, but nice weather is also ideal for naturally occurring bacteria to multiply, raising the risk of illness, warns the Washington State Department of Health. For that reason, food-safety officials in Washington state, California and Oregon advise shellfish gatherers and consumers to follow summertime health advice as they head to area beaches to gather shellfish. “Sunshine and warming waters are ideal conditions for the bacteria that cause vibriosis to multiply,” explains Jerrod Davis, director of Washington state’s Office of Shellfish and Water Protection. “This raises the risk of getting sick from eating raw or undercooked shellfish — especially oysters.” Here are some important food-safety tips for shellfish gathered in Washington state, California and Oregon:

  • Make sure the shellfish is placed on ice or refrigerated immediately after it is gathered.
  • Harvest shellfish as the tide goes out and don’t take shellfish that have been exposed by the receding tide for more than an hour.
  • Cook shellfish thoroughly, especially in the summer months, because the Vibrio parahaemolyticus bacteria are killed when shellfish have reached 145 degrees F for 15 seconds. Don’t rinse cooked shellfish with seawater because it can be re-contaminated with Vibrio.

Vibriosis symptoms usually appear within 24 hours of eating infected shellfish and may include diarrhea, stomach cramps, nausea, vomiting, headache, fever and chills. Symptoms typically last between two to seven days. People with lowered immunity, liver disease, stomach ulcers, or who take medication to reduce stomach acid are at higher risk for severe illness and should never eat raw or undercooked shellfish. Not all shellfish illnesses can be prevented by cooking. Biotoxins, which can also be found in West Coast waters depending on saltwater conditions, are not destroyed by cooking.

Sport-harvested mussel quarantines in California, Oregon

California: The annual quarantine on sport-harvested mussels gathered along the California coast began on May 1. This quarantine applies to all species of mussels harvested along the California coast, as well as all bays and estuaries.

“This quarantine is in place to protect the public against poisoning that can lead to severe illness, including coma and death,” said Dr. Ron Chapman, director of the California Department of Public Health and state health officer. “It is critical that the public honor the quarantine because the toxins found in mussels have no known antidotes and they are not reliably destroyed by cooking.”

This quarantine is intended to protect the public from paralytic shellfish poisoning (PSP) and domoic acid poisoning (DAP). Both of these toxins are linked to plankton consumed by filter-feeding animals such as bivalve shellfish (e.g., mussels and clams).

The majority of human cases of PSP illnesses occur between spring and fall.

Oregon: The coast of Oregon, from the South Jetty of the Columbia River to the California border, is also closed to mussel gathering.

Paralytic shellfish poisoning

According to information from the Oregon Health Department, warm ocean waters and calm seas are favorable conditions for a bloom of algae that produces PST. A shellfish safety closure is issued immediately if PST levels rise above the alert level of 80 micrograms per 100 grams.

Each state has up-to-date information about PST on its shellfish hotlines. (PST and vibriosis are two different health hazards that can occur in shellfish.)

Shellfish contaminated with PST can cause minor-to-severe illness or even death. PST cannot be destroyed by cooking, by adding baking soda, or by any other method of processing. PST symptoms usually begin with tingling of the mouth and tongue. Severe poisoning can result in dizziness, numbness and tingling in the arms and legs, paralysis of the arms and legs and paralysis of the muscles used for breathing. PST(s) are produced by algae and usually originate in the ocean.

Shellfish hotlines

Always check these hotlines before heading out to gather shellfish:

Washington state: 1-800-562-5632.

Oregon: 1-800-448-2474

California: 1-800-553-4133