PROVINCETOWN, Mass., July 20 (Nationwide Times) — The clearest thing the current reports establish is limited but important: New England officials and marine experts say lion’s mane jellyfish have been appearing in unusually large numbers along parts of Massachusetts and nearby beaches this summer. The evidence in the public record so far is observational — beach alerts, harbor notices, aquarium guidance and firsthand sightings — not a peer-reviewed study or a formal count of the bloom.
That matters, because it means scientists can say with confidence that people are seeing a lot of these jellyfish, but not yet exactly why this year’s surge is happening or how large it is in a strict statistical sense.
What is a lion’s mane jellyfish?
Lion’s mane jellyfish are among the largest jellyfish species, according to Smithsonian Ocean. The Smithsonian says they can stretch to about 120 feet from the top of the body to the tips of the tentacles.
That size is part of what makes them alarming when they wash up on beaches or drift near swimmers. Their tentacles can sting, and reports citing Smithsonian and Mayo Clinic guidance say the tentacles can remain dangerous after the animal dies.
Where are they being seen?
Local officials and marine organizations have said the sightings are spread across several New England communities, including the North Shore, Cape Cod, Nantucket, South Boston and parts of Maine.
In Beverly, Massachusetts, public-safety officials issued an alert telling people to keep children and pets away from stranded jellyfish and not to touch jellyfish or detached tentacles, even if they look dead.
On Cape Cod, the Sandwich harbormaster posted that lion’s mane jellyfish were appearing in unusually large numbers off the Cape. In that post, the harbormaster said reports began in May and that exceptionally high densities were seen by mid-June.
The New England Aquarium also said the jellyfish had been spotted on Massachusetts beaches and in local waters, and advised people to admire washed-up jellyfish from a safe distance.
In South Boston, the BCYF Curley Community Center said beach access was restricted after some swimmers were stung.
Why are there so many this year?
The short answer is that experts do not point to one single cause.
Pete Gawne of the New England Aquarium said the timing is hard to predict because many different factors are involved, including water temperature, prevailing currents and wind. Owen Nichols, director of Marine Fisheries Research, said dynamic regional oceanography is likely the main driver, but added that in the ocean it is rarely just one thing.
Other factors mentioned in the reports include tides and food availability, including zooplankton. That is why experts are cautious about saying any one condition caused the bloom.
Are they dangerous?
Yes. The main risk is a sting from the tentacles.
The New England Aquarium warned that lion’s mane jellyfish can give a painful sting. Public alerts in Beverly also warned people not to touch stranded jellyfish or detached tentacles.
Some reports say the tentacles can still sting for up to 25 days after the animal dies, which is why washed-up jellyfish are still treated as a hazard.
What should people do if they are stung?
The Mayo Clinic’s guidance, as repeated in the reports, recommends a few basic steps: remove visible tentacles with fine tweezers, soak the area in hot water around 110 to 113 degrees Fahrenheit, and then use hydrocortisone.
The key point from the clinic’s advice is not to handle the tentacles with bare hands and not to assume a dead jellyfish is harmless.
How unusual is this?
Local reports say the last comparable high-density lion’s mane event in Massachusetts was in 2020. But the sources available here do not give one unified measurement of how big this year’s bloom is.
Some reports describe “thousands” of jellyfish, while others use terms like “unusually large numbers” or “record numbers.” Without a formal survey or published study, those descriptions should be read as eyewitness and official observations, not as a precise scientific count.
For beachgoers, though, the practical advice is the same: keep your distance, watch for stranded jellyfish and tentacles, and follow local safety alerts before entering the water.
