Stinging Portuguese Man-o’-wars Force Swimming Closures

By: Alan Pollock

Topics: Beaches , Animals

Warning posters have been posted on Chatham’s south-side beaches, where Portuguese man-o’-wars have been spotted in numbers. ALAN POLLOCK PHOTO

WEST CHATHAM — The prevailing southwest winds, which have been blowing steadily for at least a week, have brought some unwelcome visitors to shore. Portuguese man-o-wars, jellyfish-like creatures that can deliver a powerful sting, have washed up with some regularity, prompting beach managers to warn swimmers out of the water.

Harding’s Beach in Chatham has been closed to swimmers repeatedly since last week. Lifeguards there say they sometimes find as many as 10 of the animals up on the sand in the course of a day. Swimming was prohibited for much of the day Sunday and again on Monday and Tuesday.

Warned by lifeguards that the animals have been found all over Harding’s Beach, one beachgoer said she planned to stay out of the water to be safe. Then she learned that Portuguese Man-o’-wars can sting even long after they’ve washed up on the beach.

“You mean they can sting you when they’re dead?” she said, shaking her head.

Technically a siphonophore, the Portuguese man o’ war relies on winds and tides for propulsion, suspended in the water by a tell-tale purple or blue balloon-like float. Below the float are long strands of tentacles that grow an average of 30 feet but that have been known to be 100 feet long, with stingers designed to paralyze and kill its prey: small fish and crustaceans.

While rarely deadly to people, the sting is extremely painful and can cause welts on exposed skin. And because the stinging nematocysts remain active long after the man o’ war dies, it can harm unwary beachgoers weeks after it’s washed ashore.

Chatham beach officials closed Harding’s Beach to swimming on Saturday after a number of man-o’-wars came ashore, and did so again Sunday afternoon. Swimmers were kept out of the water again on Monday and Tuesday after more were found on the beach. They were also reported at Ridgevale Beach. There have been no reports of beachgoers being stung.

There have been a few sightings this year at beaches in Harwich, though as of Tuesday morning, not enough to warrant beach closures, according to the recreation department. Lifeguards have been reminded to keep a sharp lookout.