Freshwater Jellyfish in Minnesota - Real or Fake?

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Jellyfish Video

A small freshwater jellyfish swims around a jar as science museum visitors look on.

Video by keithb

I have to admit that at first we thought it was a joke. We heard that a Science Museum volunteer had brought in a "freshwater jellyfish" to the Collector's Corner. We were even momentarily fooled when we looked at the jar full of water because it looked empty. However, as we peered closer we saw three amazing creatures about the size of a quarter bobbing around in a jar of Minnesota lake water.

Science Museum volunteer Will Hirsch and his neighbor Tim McDonough found these unique creatures in Lake Jane near the city of Lake Elmo, MN. What they found was the subject of a question to the Minnesota Department of Natural Resources a couple years ago:

In August 2003 I was fishing on a Minnesota-Ontario border lake and noticed hundreds of round, translucent discs about the size of a quarter rising to the surface. The discs had an irregular bluish central pattern and were soft, flexible, and slimy. What were they?

Jim Collinge
Detroit Lakes

You likely were looking at freshwater jellyfish (Craspedacusta sowerbii), says DNR research scientist Gary Montz. These little animals grow attached to under-water surfaces for part of their lives, then form buds that turn into the floating form, called a medusa. Freshwater jellyfish can appear in large numbers in lakes during late summer. Like ocean jellyfish, they capture their food-mainly zooplankton-with stinging -tentacles. Unlike ocean jellyfish, they cannot sting or harm you.

So what Will and Tim had discovered was the medusa form of a Craspedacusta sowerbii. These little creatures have been reported in Minnesota and almost every other state in the continental US. These animals like still waters, so they won't be found in rivers or streams. As they float around they passively feed on even tinier animals that are found in almost all lakes called zooplankton. They are easiest to spot in August and September, so keep an eye out for them next time you go swimming or fishing at your local lake.

How do they reproduce? How did they get here? What kind of water do they live in? Researchers at the Indiana University of Pennsylvania, Japan, and Australia are all studying these strange creatures to come up with answers to these questions.

Have you seen a jellyfish in any of Minnesota's lakes?

Your rating: None Average: 4.5 (8 votes)
Your rating: None Average: 4.5 (8 votes)

Your Comments, Thoughts, Questions, Ideas

Teresa's picture
Teresa says:

Cool! But do they sting like saltwater jellyfish if you touch them??

posted on Thu, 09/01/2005 - 3:46pm
bryan kennedy's picture

Freshwater jellyfish might sting. They do have the same stinging cells (cnidocytes) as the saltwater variety. However, according to the researchers at Indiana University of Pennsylvania

...we have no "hard" evidence that these organisms can penetrate human skin (though some have claimed otherwise).

posted on Thu, 09/01/2005 - 5:25pm
Anonymous's picture
Anonymous says:

truthfully I know someone who got sting and is now paralysis on one side of there body

posted on Sat, 09/11/2010 - 3:31am
Anonymous's picture
Anonymous says:

Hey..thanks for sharing..very interesting.

posted on Thu, 09/01/2005 - 7:40pm
claudia's picture
claudia says:

we heard about freshwater jellyfish in South America. To be more specific in the Amazon River.

posted on Thu, 09/01/2005 - 7:44pm
bryan kennedy's picture

Thanks for mentioning these jellyfish claudia. The jellyfish that lives in the Amazon River is the same species that we find here in Minnesota. These jellyfish were first documented by science when plants were brought back from British botanical expeditions to Brazil and Guiana. The jellyfish undoubtedly survived in the tanks used to carry the Giant Amazon Water Lily (Victoria amazonica) that went on display in the Royal Botanic Gardens at Kew, London in 1880.

However, our jellyfish is not originally native to the Amazon either. According to the Center for Lakes and Reservoirs at Portland State University it's indigenous locale is actually the Yangtze River Valley in China. So how did this little jellyfish move all over the world? The Center for Lakes and Reservoirs, suspects that migratory birds may transport them across land when the jellyfish are in their dormant polyp state.
bryan kennedy
Science Buzz Site Admin

posted on Thu, 09/01/2005 - 10:59pm
Anonymous's picture
Anonymous says:

No way is there a jellyfish in minnesota! it just cant be true!

posted on Sat, 09/03/2005 - 12:28pm
andyman's picture
andyman says:

It really is true. My wife and I were, like a previous commenter, canoeing in the BWCA (Ruby Lake, to be exact) just a week ago. We were pretty blown away by the hundreds of them we saw, as they bore such a clear resemblance to the saltwater jellyfish. Beautiful, beautiful creations.

Um, anybody ever try them deep-fried?

posted on Thu, 09/15/2005 - 1:53pm
Anonymous's picture
Anonymous says:

It most like wasn't a fresh water jellyfish if it was swimming around alot. They tend to stick to rocks and eat water fleas that swim in the water. They sting it and then eat it.\r\n

posted on Thu, 05/04/2006 - 6:09pm
Anonymous's picture
Anonymous says:

that is awsume news i did a report on minnasota that should be concidered a state symbol will it be?

posted on Sun, 05/07/2006 - 6:29pm
Anonymous's picture
Anonymous says:

My cottage is in Muskoka, Ontario, and I noticed this weekend that we have many freshwater jellyfish. I wonder how they got to my lake?!

posted on Mon, 09/05/2005 - 6:02pm
Kate's picture
Kate says:

I was just up in Haliburton, Ontario this weekend and we caught some of these jellyfish to prove that I really saw them. It was incredible, my daughter even took some to school today. HA HA. If I hadn't seen them for myself, I wouldn't have believed it either.

posted on Tue, 09/06/2005 - 8:25am
arlene's picture
arlene says:

Might we find these in freshwater ponds also?

posted on Wed, 09/07/2005 - 10:46am
bryan kennedy's picture

That's a good question. It seems that the jellyfish are able to live without water for some period of time if they are in the polyp form. So they might be found in bodies of water that periodically dry up.\r\n-----------------------------\r\nbryan kennedy\r\nScience Buzz Site Admin

posted on Wed, 09/07/2005 - 4:14pm
Anonymous's picture
Anonymous says:

How do they multiply?

posted on Sun, 09/11/2005 - 3:37pm
bryan kennedy's picture

This page has more on the reproduction cycle of the freshwater jellyfish.
bryan kennedy
Science Buzz Site Admin

posted on Mon, 09/12/2005 - 11:14am
James Satter's picture

I am sad to report that the three live freshwater jellyfish that had been on display in a jar in the Collections Gallery died last week. The specimens may be preserved for the Science Museum's collections.

posted on Mon, 09/12/2005 - 7:49am
Chuck Stickler's picture
Chuck Stickler says:

9-14-05 went out this evening and with our butterfly net were able to gather around 25 of these "jellyfish". They seem to be in 6-8 feet of water and are easy to spot if the water is like glass. Look on the sunnie side of your boat and look for air bubbles in the area. We had 5 gallon buckets and were able to reverse the net into the bucket and they came right out. Talked with a buddy who said 2 weekends ago he saw thousands in the water when he was fishing.I can't believe it myself! Too cool. on Lake Jane, Lake Elmo,Minnesota

posted on Wed, 09/14/2005 - 7:19pm
Anonymous's picture
Anonymous says:

i saw a jellyfish in my lake! it was weird, because we live on a pretty small lake in the suburbs. i thought it was a plastic bag at first... it was all blobby and pretty near the banks of the lake. how could it have gotten there?

posted on Thu, 09/15/2005 - 3:30pm
Anonymous's picture
Anonymous says:

Just seen these things this weekend in Round Lake located nearby McGregor. We seen hundreds if not thousands of these little things. VERY cool to see.

posted on Mon, 09/19/2005 - 10:00am
Anonymous's picture
Anonymous says:

Are they endangered in any way?

posted on Thu, 01/12/2006 - 9:48pm
bryan kennedy's picture

Nope. The freshwater jellyfish are quite abundant worldwide. You can check out the MnDNR website for a list of species that are endangered and/or threatened in Minnesota. Most notably this list includes the:

  • The Canada Lynx (threatened)
  • The Grey Wolf (threatened)
  • The Bald Eagle (which despite its comeback is still considered to be threatened)
  • Higgins eye pearlymussel (Endangered)
  • Minnesota dwarf trout lily (Endangered)
  • Karner blue butterfly (Endangered)

The MnDNR regularly conducts research into sensitive species in this state. Check out Minnesota Natural Heritage and Nongame Research Program to find out how you can help out with this work.

posted on Fri, 01/13/2006 - 11:00am
Anonymous's picture
Anonymous says:

I believe there is no `freshwater jellyfish in Minnesota, because it is an not very unbelieveable thing- ya feels me?

posted on Sat, 01/21/2006 - 6:20pm
Anonymous's picture
Anonymous says:


posted on Thu, 07/20/2006 - 1:36pm
Tiffany's picture
Tiffany says:

I HAVE one of these things! It is endlessly fascinating, but how do I find food for it? Can someone email me and tell me how to feed my little squishy? So far, I am just putting him in fresh lake water every few days. He is still alive after two weeks, but I want to be sure. He is about the size of a quarter when he is open (yes, I know it isn't really a "he") and can get so tiny when he is closed that the jar looks empty. The DNR in Minn was to call me with tips, but they never did. Thanks!!!!!

posted on Sat, 08/19/2006 - 8:06am
Anonymous's picture
Anonymous says:

What's ANOTHER fear to swimming?

posted on Sat, 08/19/2006 - 1:45pm
Anonymous's picture
Anonymous says:

my family has a lake house in Indiana, we found 2 species that were exactly identical to jellyfish. they were the size of a quarter though.

posted on Tue, 09/05/2006 - 8:25pm
Rev SD Harduk's picture
Rev SD Harduk says:

Very cool! I saw these a couple of years ago in a lake in Michigan while fishing. They are so transparent that it's easy to miss them. I believe it was early September and very warm out.

posted on Fri, 01/26/2007 - 12:01pm
Petey's picture
Petey says:

I thought that i would mention the fact that these same jellyfish were spotted by me my dad and brother, in a lake up here in michigan. the lake is called selkirk lake, and is near wayland. when we saw these jellyfish was about two years ago, and there were THOUSANDS. so yea i just thought i would mention them being here too.... bye

posted on Sun, 04/08/2007 - 9:34am
Cottager's picture
Cottager says:

Freshwater jellyfish show up in our lake in Ontario every 2-7 years. They're small-- about the size (and shape) of a contact lense. Our lake is fairly small and doesn't get deeper than about 50 feet. They like to float near the surface in the middle of the lake, and in a good year, there are thousands. They don't sting, and can be picked up with bare hands.

posted on Tue, 08/07/2007 - 5:13pm
Anonymous's picture
Anonymous says:

Well we have em here in New Hampshire lakes too.
I just saw my first ones because there was a "bloom" yesterday, August 11, 2007.
I couldn't believe my eyes. Never heard of Freshwater jellyfish.
I have one of the little fellows in a plastic cup. I hope I can keep it alive.
If anyone knows how, please post it.

posted on Sun, 08/12/2007 - 2:14am
Anonymous's picture
Anonymous says:

We have them on our lake too. I was out swimming on Saturday and saw nothing, but Sunday we had swarms of them on the lake. We live on a rather pristine electric motor lake that is spring fed and cooler and from some of my reading, it appears this is the type of lake they thrive in, but the first I have seen. I was too freaked to swim, because I didn't know if they were stinging or not (hence the research - guess I should feel free to swim again).

Does anyone know if they stick around long or this just a week long occurrence? Still just a bit skittish about swimming.....

posted on Mon, 08/27/2007 - 5:47am
Anonymous's picture
Anonymous says:

Just wondering...I live in Canada. When the frost hits up here does that mean that the jellyfish die off???
Until another bird transfer them into our lake again??
Do these Jellyfish get eaten by the fish??
I really dont like to swim in the lake when I see them...its creepy.

posted on Tue, 08/28/2007 - 2:21pm
Bill Williamson's picture
Bill Williamson says:

We found some of the fresh water jelly fish in Michigan , today is 9-3-07 , we where on Diamond lake near Hesperia, around 10:00 Am, Seen 100's maybe 1000's of them.

posted on Mon, 09/03/2007 - 5:12pm
Piglotte's picture
Piglotte says:

I was visiting friends south of Jackson Michigan. The jellies were the size of a nickel and active. It was approx. 6pm on 9-3-07 when we saw them. There were hundreds of thousands. I've been scuba diving in inland lakes for years and had never had a sighting, neither had the lake house friends. way cool!

posted on Wed, 09/05/2007 - 6:38pm
 Maureen's picture
Maureen says:

My husband and I found some of these astonishing creatures in a small lake at the Yankee Springs Recreation Area in Barry County Michigan last year. We found some again this year in the same lake. I told my husband that they looked like jellyfish. He talked to a science teacher at The local middle school where he works. The science teacher did not think they were jellyfish---believing there were no freshwater jellyfish. We took some in to him and with a little research discovered that they were jellyfish. I was astounded when I first saw them, never having heard of fresh water jellyfish. I have been on many lakes in southwesten Michigan over the last 50 years and have never seen them before. Evidently there have been alot of sightings in this area lately---Selkirk Lake mentioned in an earlier posting is very close to Yankee Springs. Our local middle school is abuzz aboput this---something interesting for the kids to see as they start back to school.

posted on Wed, 09/05/2007 - 10:04pm
P Yeiter's picture
P Yeiter says:

I will also vouch for seeing thousands of them in Diamond Lake, near White cloud Michigan.

posted on Thu, 09/06/2007 - 4:06pm
Lindsey's picture
Lindsey says:

We saw some a couple weeks ago in Lake Dodo, near Cotton, Minnesota. It was really quite amazing - I had no idea that freshwater jellyfish existed, in Minnesota no less.

posted on Thu, 09/13/2007 - 2:14pm
Anonymous's picture
Anonymous says:

My family and I have seen millions in our lake in Lapeer County, Mi. So many, that I wondered if it can be good for the lake.

posted on Fri, 10/12/2007 - 5:11pm
Peter Fagrelius's picture
Peter Fagrelius says:

Oh my gosh I was researching this for a school project and i saw myself in the video, I remember seeing this that day and I'm the chubby kid with the green hat.

posted on Mon, 02/18/2008 - 4:08pm
S.O.'s picture
S.O. says:

WOW, thats me, im the kid that you first see in the video with the TCA tigers shirt one

and my friend is in it also(peter f.)

posted on Wed, 02/20/2008 - 5:31pm
bryan kennedy's picture

Cool! How did you end up back on this page? Were you looking for information on freshwater jellyfish?

posted on Thu, 02/21/2008 - 8:28am
S.O.'s picture
S.O. says:

no, my friend Peter told me i was in the video so i went to the page after he gave me the URL

posted on Thu, 02/21/2008 - 6:08pm
scott mackellar's picture
scott mackellar says:

My friend and i are on a quest this summer to find a pocket of these jellyfish he has spotted 2x in eastern ontario. What would be your advice if we think the creatures are of a different species?? Does canada have experts looking into these creatures?

posted on Fri, 03/28/2008 - 12:38pm
Greggie-Pi's picture
Greggie-Pi says:

I know... jellyfish are totally awesome creatures. my favorite jellyfish are the pink ones! did you know: that jelly fish harden once they are dead and have drifted to shore? i was with my cousin on a beach and poked all of the jellyfish in the area...they were hard as a rock!! Amazing!!

posted on Fri, 03/28/2008 - 2:39pm
Doctor Doctor's picture
Doctor Doctor says:

That's a great question! I'm affraid that don't know the answer to that one, but I highly doubt that someone would be able to find a jellyfish in Minnesota.

posted on Fri, 03/28/2008 - 2:47pm
Willy Lee O.'s picture
Willy Lee O. says:

unusual underwater aquatic organisms are so fascinating! who would've thought that there would be real LIVE jellyfish right in our surrounding communities? i believe that i will go into environmental studies when i grow up.

posted on Fri, 03/28/2008 - 2:54pm
Anonymous's picture
Anonymous says:

ya they r real we hav them in ky i just 1st saw 1 yesterday and know im lookin up if they are piosinis

posted on Sun, 08/17/2008 - 4:46pm
Anonymous's picture
Anonymous says:

Just spotted them in a small lake here in southern West Virginia. Couldn't believe my eyes! So had to run to the internet to research the finding. Wish I had caught some to observe.

posted on Mon, 08/18/2008 - 7:37pm
Anonymous's picture
Anonymous says:

Found some last week in a small lake in PA! Does anyone know if they've been found in PA before?

posted on Mon, 08/25/2008 - 5:57am
Eric Rohloff's picture

My mother runs a campground on Selkirk Lake in Shelbyville, MI. I have witnessed the jelly fish in the Lake for over 30 years. They don't occur every year but have in recent years shown up in large numbers. I have video of them and my boys are always intrigued by the amount of jellyfih (Millions). They usually show up in early Sept. If you search youtube people are posting videos. From what heard they sit dormant on the bottom of lakes waiting for the water temp and food source to be just right.

posted on Sat, 12/20/2008 - 3:53pm
Kelsey's picture
Kelsey says:

wow!!!! i never even saw a jellyfish before!!!!!!!!

posted on Sat, 01/31/2009 - 5:51pm
Anonymous's picture
Anonymous says:

Freshwater Jellyfish have been documented in PA since 1884. They were first seen near Philadelphia and have since spread to thousands of waterways throughout the commonwealth. The medusa stage is easiest to find, and I recently watched a group swimming in a county owned quarry pond near Alburtis, PA. If you're lucky enough to find some, share the experience with others, they'll be amazed !

posted on Sun, 09/06/2009 - 11:48am
Craig's picture
Craig says:

Found in Gladwin county Michigan this labor day! Gladwin is in middle of lower peninsula. Went out today and spotted hundreds. Held one in my stinging sensation. Does anyone know if they survive through the winter,or do they die off from the cold? Read on different web sites about these creatures,but vague on survival.

posted on Thu, 09/10/2009 - 6:59pm
Lorna McCrea's picture
Lorna McCrea says:

Freshwater jellyfish, likely the same genus, were seen on Labour Day weekend in Lac Lapeche, Quebec, Canada in the year 2004 and again in 2009, at the same spot, the same time of year, by two other parties, while canoeing.

Specimens were transparent, thumbnail-sized medusae, with yellow X-shaped innards, moving up to the surface.

Could be a recent introduction by birds or boats, or a relict of 10,000 years ago when this part of Gatineau Park was inundated by the post-glacial Champlain Sea.

Interested in similar sightings in the Canadian Shield by other observers. (Honours Biology grad now retired)

posted on Mon, 11/30/2009 - 9:49pm
Anonymous's picture
Anonymous says:

were do these jelly fish come from? ive only seen them once on sand lake minnesota about five years ago

posted on Mon, 02/15/2010 - 6:05am
Anonymous's picture
Anonymous says:

Saw blue jelliefish just west of port loring in september of last year. The local people who owned the adjacent property had not seen them in the past. sort of looked like four slim leaves joined together at one end and attached to the outer ring at the other end. port loring is near georgian bay in ontario.

posted on Sun, 03/21/2010 - 9:37pm
Anonymous's picture
Anonymous says:

We just spotted jellyfish in a large springfed pond just outside London, Ontario. I didn't beleive it when I was first told by the kids they had seen jellyfish, we swim there all the time and I had never seen anything, nor had we heard of freshwater jellyfish. This is the first time we've spotted them and have had this property for about 7 years. Is this something we should expect to see from now on, and why their sudden appearance ?

posted on Sun, 08/01/2010 - 9:21pm
Anonymous's picture
Anonymous says:

I just got back from a trip to Minnesota and actually took a picture of a Jellyfish on the St. Croix River that had washed up on shore! These do exists! I would have never guessed if I had not seen it with my own eyes or had the picture to prove it!! 8-7-10

posted on Sat, 08/07/2010 - 7:57pm
Sarah & Christina's picture
Sarah & Christina says:

ME and my friend(christina) were out by my fresh water pond and found little jelly fish we do not wanna touch them because we are not sure if they sting or not.

posted on Fri, 08/13/2010 - 6:56pm
Anonymous's picture
Anonymous says:

I am in Maine, and we have a large number of these jellyfish in a small lake that we camp on (Keenes Lake). I have never seen anything like it until this year. There are litterally THOUSANDS of these things in the lake.... kinda gross for swimming..... but cool to look at. So far, no one has been stung.

posted on Mon, 08/30/2010 - 7:12am
Anonymous's picture
Anonymous says:

I live in Rockford, MICHIGAN on Scram Lake and we have millions in our lake right now, 8/31/2010.

posted on Tue, 08/31/2010 - 8:11pm
Bob.M's picture
Bob.M says:

just found them in a small private Pennsylvania lake that i have been swimming in for 44 yrs. my kids bet me a million bucks. good thing i did not take the bet. 9/1/2010

posted on Wed, 09/01/2010 - 5:56pm
Anonymous's picture
Anonymous says:

Yes I am so glad to find this site in my search on the internet for this fresh water jelly fish, thought we were seeing things when we went fishing, we seen them in a lake called cariboo lake near Sault Ste Marie Ontario, my questions are is this going to ruin our fishing and is it a new speicies to our lakes?

posted on Tue, 09/07/2010 - 6:11am
Anonymous's picture
Anonymous says:


posted on Mon, 09/20/2010 - 9:25am
Chuck, Ely, MN's picture
Chuck, Ely, MN says:

oN ABOUT 9/15/10 we saw very numerous jellyfish in a shallow bay of Lac La Croix. What other lakes have they been seen.?

posted on Mon, 10/18/2010 - 7:37am
Anonymous's picture
Anonymous says:

We have these in Kansas also, at first I too was a non believer, but after going to Cedar Creek Lake and seeing them for myself, I now believe it. So I can now say, I am not going to be swimming there. Besides it's full of Cedar trees, hence the name.

posted on Sat, 11/13/2010 - 3:08pm
Anonymous's picture
Anonymous says:

I saw hundreds of these in Lake Kashagawigamog, Ontario (between Minden and Haliburton) Sept. 10, 2011. They were 15 to 20mm across (penny size to nickel size)
They were clear, with 4 green spots in the middle of their bodies.
They were a few inches below the surface in 5 feet of water.

posted on Sun, 09/18/2011 - 7:40pm
SteveO's picture
SteveO says:

There are thousands of them swimming in the calm water on the west end of Dodo lake right now 3:30 pm 8/10/12. It is a small lake located between Canyon and Cotton Minnesota. We caught several in a cup; they swim around and pulsate like normal jellyfish. The sizes range from 1/4-1/2 inch in diameter.

posted on Fri, 08/10/2012 - 2:36pm

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