Officials in Gloucester issued a warning to swimmers at Niles Beach and nearby areas after lion’s mane jellyfish were seen in the outer harbor, Gloucester Beaches’s announced in a Facebook post.
“These jellyfish can deliver painful stings—even after they’ve washed ashore,” the statement posted July 12 reads. “Please use caution and avoid any jellyfish you may see.”
Last month, a nearly five-foot-wide lion’s mane jellyfish washed up on the shores of Willard Beach in South Portland, Maine.
According to the Aquarium of the Pacific, lion’s mane jellyfish are the largest sea jelly among over 200 species. They are found worldwide, save for tropical waters.
“They can sting people, but they’re not fatal,” said Larry Madin, an emeritus scientist at the Woods Hole Oceanographic Institution. “They’re not as serious a jellyfish as a Portuguese Man O’ War.”
But, he said, the sting is still painful.
“It’s best not to get too close,” he said in a phone interview.
Officials in Gloucester added that they’re currently reaching out to the National Oceanic and Atmospheric Administration for guidance on dealing with the jellyfish.
Madin said that prevailing currents can bring jellyfish closer to shore, interfering with people swimming.
Even if discovered on the beach, Madin said lion’s mane jellyfish are still dangerous.
“The tentacles with stinging cells can still sting as long as they’re still wet,” he said. “Don’t pick it up.”
All beaches in Gloucester are open, officials said.
“City staff are monitoring the situation closely this morning and will update as needed,” the post reads.
Truman Dickerson can be reached at truman.dickerson@globe.com.