Jellyfish spotted in Northern California reservoir, experts say. Are they dangerous?

It was an unexpected sight for Casey Neet and his 8-year-old daughter paddleboarding in an Eldorado National Forest reservoir: Hundreds of transparent white circular blobs drifted in the serene freshwater.

Neet, who thought they might be pollen or egg sacks at first glance, told The Sacramento Bee that he leaned in closer and realized freshwater jellyfish floated alongside them.

It was a species known as peach blossom fish that have been spotted across North America but rarely in that area, said Maura Santora, an aquatic biologist with the U.S. Forest Service, who also conferred with the California Department of Fish and Wildlife to make the identification on the recent finding.

“This is my first time hearing about them in Stumpy Meadows Reservoir during my 9 years on the Eldorado National Forest,” Santora wrote in an email.

A Fish and Wildlife spokesman did not immediately return a call about the jellyfish. The freshwater jellyfish are not considered dangerous to humans, and their small tentacles will likely not penetrate human skin, said the U.S. Geological Survey.

People have reported the freshwater jellyfish in bodies of water in the Eldorado National Forest, but those sightings haven’t all been verified, she added.

Indigenous to China, peach blossom fish are highly concentrated along the East Coast, according to a USGS map. The small animals have been reported in the American River and upper Cosumnes River, but none so far in the Eldorado National Forest, according to the USGS. Stumpy Meadows Reservoir is about 10 miles north of Pollock Pines.

Typically, peach blossom jellyfish cling to boats and other vessels used for recreational activities, Santora said. It’s a non-native species to the area, and Santora encouraged residents to clean, drain and dry their aquatic equipment when going from one body of water to another.

Neet, who posted about the jellyfish on Facebook, said every time he looks at his phone a reporter is asking him to speak about the jellyfish. The social media post has garnered dozens of reactions and comments since he posted it on Sept. 23.

The invertebrates have Neet concerned because the reservoir ultimately ends up as their drinking water.

But the jellyfish sightings won’t stop Neet and his daughter from enjoying the reservoir — they cannot go swimming, but can certainly paddleboard, he said.