Freshwater Jellyfish: Species of the Week


Freshwater jellyfish: don't worry, it won't sting you. Photo: OpenCage/Wikimedia Commons


Freshwater jellyfish have been spotted in Ohio ponds, alarming locals and surprising old timers. The local Newark Advocate quoted Frank Snelling, who has lived in the area for years, as saying, “I told him, ‘You better drink a beer. There aren’t jellyfish in Ohio.'”

freshwater species of the weekActually there are, because small freshwater jellyfish (Craspedacusta sowerbii) are native to Ohio as well as many other parts of the world. 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.

So next time you take a dip in an old quarry or swimming hole, see if you can find any one-inch freshwater jellyfish. They won’t sting you, and they’re part of a healthy ecosystem.

Learn about the golden jellyfish in Palau’s saltwater lake>> 

See amazing jellyfish photos>>


Picture of Craspedacusta sowerbyi freshwater jellyfish
Freshwater jellyfish prefer slow-moving, clean water and can be found all around the world. Photo: J. Michael Tracy, Wikimedia Commons


Brian Clark Howard covers the environment for National Geographic. He previously served as an editor for TheDailyGreen.com and E/The Environmental Magazine, and has written for TheAtlantic.com, FastCompany.com, PopularMechanics.com, Yahoo!, MSN, Miller-McCune and elsewhere. He is the co-author of six books, including Geothermal HVACGreen LightingBuild Your Own Small Wind Power System, and Rock Your Ugly Christmas Sweater.


  • Ima Ryma

    Craspedecusta sowerbii,
    In the Cnidaria phylum,
    AKA hydromedusae,
    Freshwater jellyfish, in sum.
    We like to show up unannounced,
    Catching a ride on what we can,
    Till in some water we get bounced.
    Tiz not a real well thought out plan.
    The locals kinda get freaked out
    When they first get a peek at us,
    ‘Fraid they’re gonna get stung, no doubt –
    But just if we can eat the cuss.

    We’re only about one inch big,
    So don’t do the human lunch gig.

  • Jay

    These Jellies have showed up in this lake. Never before. Schools of THOUSANDS especialy when sun is out. Its freaky and I hope it wont be worst next year!


    I love your article. I just saw the fresh water jelly fish last Friday in a locally pound in my area, it was millions of then very happy swimming around my boat. My Science Prof. Beluzo was very happy to see then it was like he saw a 100$ bill in the water. It was a great article you wrote and amazing pictures. I am so happy to find it in my assignment research you save my life with your incredible article. Thank you..they are amazing creatures ..love them, I am going to make a painting and please let me know if you want to see it, maybe you can utilize for some illustrations or cover of your book. Than you for it!!

    • Thanks Andres! I’d love to see your painting. When you’re done, send it over.

  • Irene Klarich

    Saw these friendly little fellas for the first time this summer in Lake Oroville, California. When we anchor the boat to fish, they come around to see what we are! Saw them in groups of 3 or 4. Never seen them before in Lake Oroville till this year. Had to look it up…glad I did!

  • Chandra

    A tripod is esanetisl. In dark light, any amount of camera shake is ten times more disastrous to your photograph. Don’t use Flash, it will cause glare on the glass and most likely scare the fishies half to death!Like these guys have said, up the ISO/ASA film speed to 400 or above this allows for better photographs in limited light. There’s never a specific or specific setting for photography, its so dependant on available light etc so the most important thing you can do is just keep experimenting, and take a little notepad with you so you can write down what exposures you used for each shot and state what the light was like then in future, if you are in a similar situation, you can get your notes out and use it as a reference.Hope your trip is fun!

  • Donna

    I seen millions of these in the little kanawha river in Parkersburg wv. They were not on the bottom the were from the top of the water to about 2 feet down. This was 20 years ago and no one believed me.

  • tory asher

    we were out fishing yesterday and we seen a bunch of 1″jellyfish

  • Robert Grove

    These 1″ jelly fish are in Allatoona Lake also. We have seen them more abundant in the stamp creek area of the lake.

  • gabe

    iv seen one before

  • Amy Tavares

    I just saw some of these little jellies in Sandiff. Amazing! I didn’t know they could be so small and in fresh water, nice article 🙂

  • caleb king

    this post was about my uncles pond, there were thousands of them they looked like little contacts. we even took a small paddle boat and you could grab a handful and wouldn’t get stung.

  • Ben

    I have about a 2 acre pond and every couple years I see them at the surface. I asked everybody around and no one ever saw or heard of them, so I’m glad to see that it is safe to keep on swimming

  • Pam

    Just spotted some for the first time in our lake this year. We’ve been on the lake 20 years.

  • Garnet Tyler

    I have seen freshwater jellyfish in the Summerville lake.

  • Vic

    I think these freshwater jellyfish are cancer tumors. Just as when you remove a cancer tumor if you dont get all the spiny like tenichles a whole new tumor can re appear just like when you cut a jelly fish up the pieces can re generate a whole new jellyfish

  • Guy QWirt

    1st one seen in 17 years living here

  • Guy QWirt

    First one seen in 17 years living here

  • KY lady

    We have them in our pond, about 4-5 acres spring fed. Good to know it means the water quality is good! Thanks for the article.

  • Careline

    After seeing a video from a lake that I visit quite often in Glen Rose TX. They are amazing and I want them. The lake is called Wheeler Branch Park in Glen Rose TX, if anybody wants to visit

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