MONMOUTH, N.J. (WPVI) --Clinging jellyfish are multiplying in the river waters of New Jersey.
However, beach-goers will have little reason to worry. The New Jersey Department of Environmental Protection says the jellyfish have only been found in interior rivers, where they thrive. There have been no beach sightings.
The jellyfish carry a very painful and sometimes dangerous sting that in extreme cases can lead to kidney failure.
Emily Sgro was one of the first to notice these dime-size creatures along the Shrewsbury River in Monmouth Beach.
"I do not want to go directly in the water for the rest of the summer," said Emily Sgro, a Monmouth Beach resident.
"We saw one of them and I figured we should get that out of the water as soon as possible. Then we found about five or 10 more in the area, then after that found about 50 within a half hour," Sgro said.
The jellyfish may have arrived here via ship.
"Looks like we may have some areas that have a lot of these individuals," said Dr. Paul Bologna, a Marine Biologist at Montclair State University.
Dr. Bologna studies jellyfish for a living.
"One of the first questions that we want to know is sort of where they are, what's their density, are there sort of hot spots within these regions," Dr. Bologna said.
The timing of this jellyfish invasion is another concern. A man was already hospitalized on June 10th from a sting in this same area.
"Now the summer season begins that if you're in one of these areas that might have high abundances, you're going to increase the potential of encountering them and potentially getting a pretty big sting," Dr. Bologna said.
It turns out that clinging jellyfish don't like the rough waters of the ocean. Instead, they gravitate toward these calm, back bay waters like here along the Shrewsbury River.
"So we don't want to discourage anybody from going to the ocean beaches," Dr. Bologna said.
But if you do spend time along the back bays and happen to be stung, know the symptoms. While the pain will tend to subside from a typical jellyfish sting, that's not the case with the clinging variety.
"That pain doesn't subside. It sort of escalates upwards. That's one of those major signals that it might be time to seek medical treatment," Dr. Bologna said.
And don't expect them to go away anytime soon.
"If they're there and they're established like these guys are, they're here to stay," Dr. Bologna said.