The Ephemeral Freshwater Jellyfish

The Ephemeral Freshwater Jellyfish

“A jellyfish, if you watch it long enough, begins to look like a heart beating. It’s their pulse, the way they contract swiftly, then release. Like a ghost heart — a heart you can see right through, right into some other world where everything you ever lost has gone to hide.” From “The Thing About Jellyfish,” by Ali Benjamin

From time to time my friend, Dick Waterman, will email me about something he has happened upon in the natural world. Sometimes it’s a question, but more often it’s a recent discovery near his home. He lives in a beautiful part of The Last Green Valley National Heritage Corridor, and his encounters just outside his doorstep are always informative. He is fortunate to have a variety of diverse habitats near his house, including a large beaver pond and acres of forestland. He recently emailed me about freshwater jellyfish, so I ventured to his place to learn more.

Dick wrote “I strive to learn something every day, and my wish was fulfilled this past Saturday when while observing the clear, still waters of the Baltic Reservoir just down the street from me, I noticed what appeared to be small jellyfish, about the size of a penny, drifting about. They looked similar in shape to the saltwater moon jellies we see in late summer, but much, much smaller. They reminded me of a mountain laurel flower blossom, only transparent.”

I was not surprised when Dick said he researched freshwater jellyfish. “In fact, upon reading about them, the organism is called the peach blossom jellyfish in China, where it was originally found, but is, according to the article I read online, found all over the world now.”

I had never been to Baltic Reservoir before and was hoping to see the freshwater jellyfish. We met at Dick’s house and drove the short mile to the reservoir, a beautiful 25-acre pond surrounded by 250 acres of forest. The entire property is under the jurisdiction of the Sprague Water & Sewer Authority and the Sprague Conservation & Agriculture Commission. Despite its name, Baltic Reservoir is no longer a water supply to the village of Baltic, and the area is now used for passive recreation. It was constructed in 1900 and the long concrete dam has recently been refurbished. It is a beautiful place.

The reservoir is not the only waterbody in the region where the peach blossom freshwater jellyfish has taken residence. According to a 1999 report, the United States Geological Survey (USGS) has collected the peach blossom jellyfish in a few ponds within the Quinebaug, Shetucket and Thames River drainage areas.

From the wooded parking area, we hiked down a short path to the pond and from there circumnavigated the water by a well-tended footpath that has probably been traversed by many anglers. We met two of them coming and going. At several locations we were able to get close to the water and when the wind was still you could see down a few feet into the clear water. If there were freshwater jellyfish about that day, they were down in the depths and not interested in showing their shimmering pulses for two visitors from terra firma.

I looked around for more information about this creature of our freshwater ponds and found information from two sources beyond the boundaries of The Last Green Valley.

The New Hampshire Department of Environmental Services (NHDES) reported in 2019 the peach blossom freshwater jellyfish was first discovered in the United States in 1908. While found in many of the contiguous 48 states, they are most common in eastern temperate states. They have been reported in 63 waterbodies according to the NHDES. Typically, they appear in small ponds and some reports say they are found in old quarries, while other reports say they are found in new reservoirs. “Don’t count on seeing them in the same pond two years in a row; they may appear again a few years or not at all. Wherever they are found, many scientists agree, they are elusive.”

Another source for information about the peach blossom freshwater jellyfish was the esteemed National Geographic and its Newsroom Blog from August 2012.

“Marty Lundquist, a fisheries biologist with the Ohio Department of Natural Resources Wildlife Division, told the Advocate’ that his agency gets called about the small jellies every year. Lundquist said the jellyfish like to live in ponds with good water quality, and that they usually hang out near the bottom. They prefer calm water and are also found in flooded quarries and lakes. They enter new habitats as polyps stuck to vegetation or birds, or transported in bait buckets. The freshwater jellies do have stinging cells, but they are so small that they usually don’t hurt vertebrates (the whole animal is only about 1 inch [20–25 mm] across).

The jellies live off copepods and other zooplankton, which they paralyze with their ring of 400 slender tentacles. They pull their prey into their mouth, which hangs below the translucent bell. Freshwater jellyfish may have a whitish or greenish tinge. These small animals have been reported in many countries around the world, from Thailand to India to Brazil, and in most U.S. states and Canadian provinces. Like many jellyfish, this species has a complex lifecycle that includes a polyp phase, a larva phase, eggs, and the most familiar, the medusa (the one that looks like a jellyfish). When conditions get tough, they can wait it out in a dormant resting phase at the bottom.”

While walking around Baltic Reservoir with Dick Waterman he ventured that “as little as I know about the organism, I suspect that its appearance is ephemeral. But I would guess that water temperature and other factors determine when one might be lucky enough to observe them.  Additionally, if the waters are not calm, it would probably be near impossible to see them.”

I hope that someday — likely when least expected — I too will see the elusive and ephemeral peach blossom freshwater jellyfish. Perhaps I’ll be paddling a clean clear pond on a calm sunny August afternoon when I’ll see the penny-sized translucent creatures pulsing under my paddle. I’ll remember to give Dick a call to let him know I too have seen the freshwater peach blossom.

We live in a beautiful place called The Last Green Valley, our very own homegrown National Park. I hope you’ll join me as we enjoy it, care for it, and pass it on.

Information for this column was provided by Richard Waterman, the 1999 USGS Craspedacusta sowerbyi collection data for Connecticut, “Freshwater Jellyfish: National Geographic Newsroom Species of the Week, August 2012,” by Brian Clark Howard, and The New Hampshire Department of Environmental Services Freshwater Jellyfish Fact Sheet.

Bill Reid is the Chief Ranger of The Last Green Valley National Heritage Corridor and has lived in the region for more than 35 years. He can be reached at


Get Connected

Sign up for our newsletter

"*" indicates required fields