Lion’s mane jellyfish have been spotted along Swampscott beaches — and across the North Shore — creating an obstacle course for beachgoers.
Lion’s mane jellyfish have been spotted at Phillips, Fisherman’s and Whales beaches. They vary in size but are recognizable by their clear edges and darker brown centers.
According to the Smithsonian, lion’s mane jellyfish are among the largest species of the animal. The species is named for its long, trailing tentacles. They often remain near the surface and are common in Massachusetts coastal waters during the summer. The largest recorded specimen was measured off of the coast of Massachusetts in 1865, with a bell diameter of 7 feet and tentacles that were 120 feet long.
Contact with a lion’s mane jellyfish can cause temporary pain and redness. Their tentacles may retain the ability to sting for up to 25 days after detaching from a jellyfish. According to the Smithsonian, the tentacles contain neurotoxins that can cause effects ranging from a rash to respiratory issues.
Jellyfish have limited swimming ability and largely drift with tides and currents. Onshore winds and incoming tides can trap the jellyfish into the shallow waters, leading them to wind up on the sand.
Warm weather also accelerates jellyfish life cycles, causing population blooms to mature faster. As a result, jellyfish populations can increase more rapidly.
“Through June 23, the nearby Marblehead, MA weather observing station has recorded an average temperature (combining high and low temperatures for the month) of 69.2 degrees, which is six degrees above average,” Erica Grow Cei, the public affairs specialist with NOAA’s National Weather Service, told the Swampscott Tides. “The warmest average June temperature ever observed at Marblehead was 70.3 degrees Fahrenheit in 1999. And, so far this is the warmest June for Marblehead since 2001.”
Swampscott is not the only one witnessing an increased number of jellyfish this summer. Several jellyfish stings have prompted officials to restrict water access for minors at the Boston Center for Youth and Families’ Curley Beach.
“Jellyfish are a natural part of the marine environment, and their presence can vary with tides, currents, and weather conditions,” the agency said in a statement. “While beach operations remain open at this time, we encourage all visitors to remain alert and follow instructions from lifeguards and staff. If you experience a jellyfish sting or require assistance, please notify a lifeguard or staff member immediately.”
Cape Cod is also seeing an influx of lion’s mane jellyfish, with Great Marsh Kayak Tours telling MassLive there are “multiple thousands of them.”
The phenomenon isn’t unprecedented. More locally, in 2020, the Department of Conservation and Recreation warned the public about lion’s mane jellyfish at Nahant Beach, posting purple flags to alert visitors to dangerous marine animals. Similar warning flags were also raised at King’s Beach in Lynn.
Swampscott beaches are open for the season. During the summer, Swampscott residents are able to enjoy the town’s six beaches:
- Eisman’s/New Ocean Beach: Open for swimming, lifeguards on duty seven days a week from late-June through mid-August from 10 a.m. to 4 p.m.
- Fisherman’s Beach: Boating and swimming, lifeguard on duty weekends only from late-June through mid-August from 10 a.m. to 4 p.m.
- King’s Beach: Public beach, swimming and no boating, no lifeguard on duty
- Phillips’ Beach: Swimming, lifeguard on duty seven days a week from late-June through mid-August from 10 a.m. to 4 p.m.
- Preston Beach: Swimming, no lifeguard on duty
- Whales Beach: Swimming, no lifeguard on duty
Beach parking stickers are required for:
- Preston Beach: Northbound side of Atlantic Avenue to the Marblehead line
- Phillips Beach: Ocean side of Ocean Avenue, between posted signs
- Whales / Eisman’s / New Ocean House: Parking lot next to the Phillips Park football field
- Fisherman’s Beach: Parking lot adjacent to the Fish House
- Recreation Parking: One side of Columbia Street next to the railroad station
