With many people heading to their favorite beach for the final fling of the summer this holiday weekend, fresh shellfish fans will no doubt be out in force harvesting clams, oysters, mussels and other delicacies.

Photo courtesy of the University of Florida

But unseen dangers lurk in the coastal waters and creatures that call them home. Pieces of coastline from New England to the Gulf Coast to the Pacific Northwest are closed to shellfish harvesting because of dangerously high levels of paralytic shellfish poison, Vibrio bacteria and other toxins.

Some of the toxins, such as paralytic shellfish poison (PSP) are not rendered harmless by cooking. Other pathogens and toxins can survive freezing. Vibrio bacteria can sometimes be killed by cooking. Fish and shellfish that are contaminated with marine toxins do not look or smell bad. The microscopic pathogens cannot be seen with the naked eye.

Beach lovers who are looking forward to a clambake, steamed mussels or any other seafood they plan to harvest themselves should check local and state advisories for harvest closure notices.

For example, both Maine and Washington currently have beaches closed to recreational harvesting of certain shellfish species because of paralytic shellfish poison levels. The toxin is quick acting and can paralyze respiratory muscles, resulting in death.

Both states offer constantly updates maps of beaches and fishing areas and the status of toxins and harvest closures related to them. In Maine, the Department of Marine Resources is responsible for monitoring shellfish beaches. In Washington, the Department of Health tracks marine toxin levels and posts harvest closures.

Razor clam diggers in Washington state are at increasing risk of infections from handling shellfish. Photo courtesy of NOAA

In other coastal states, various departments offer similar maps and updates. Even if specific areas are not closed to recreational harvesting, shellfish there can be contaminated with Vibrio bacteria — particularly oysters, which some people consume raw.

“For those who enjoy collecting and consuming their own shellfish, it’s important that they follow a few simple measures to stay healthy,” Rick Porso, director of the Washington state Office of Environmental Health and Safety, said in a news release urging caution during the Labor Day holiday weekend.

“Before heading to the beach, people who gather their own shellfish should check the DOH Shellfish Safety Map to determine if any areas are closed. Shellfish gathered from open and approved areas should be harvested as the tide goes out, chilled as soon as possible, and cooked at 145 degrees F for 15 seconds to destroy Vibrio bacteria.”

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