Barbs and Backlashes

Freshwater jellyfish? by whitetips
August 13, 2010, 10:20 am
Filed under: Fishing

Would you believe we have jellyfish in Nebraska?  Actually if you look in the right places you can find a lot.  Jellyfish belong to the Cnidaria family and some species of jellyfish live part of their lives as stationary polyps and part of their lives as mobile medusa that most folks think of when they think of “jellyfish”.  There are species of freshwater Cnidarians, Hydra, that spend their entire lives as the stationary polyps.

I have seen samples of “macroinvertebrates”, bugs and other critters, floating around in Nebraska waters that had thousands of Hydra mixed in with all the midge larvae, mayfly larvae, scuds and other critters that were swimming around.  A person had to look close to recognize those Hydra however, as they were about this big —- .

There are a species of the classic, medusa-jellyfish that can be found in Nebraska waters as well.  I have seen these on one occasion back in my youth (yes, that was a LONG time ago).  I saw those jellyfish bobbing around in a small sandpit just north of North Platte.  The other reports that I have heard of these freshwater jellyfish have all come from Platte River sandpits.

Again you can see that those jellyfish are relatively small and you have to be observant to even notice them.  If you want to learn more about these curiosities here is a website that tells you all about them, .  Would you believe that these freshwater medusa jellyfish are actually considered non-native, invasive species?!  However, they were first documented in United States waters in 1880 and have been found in 44 states.  Any impact these freshwater jellyfish might have on native species or our aquatic ecosystems is unknown and likely minimal.  These jellyfish likely exist in the polyp form much of the time and only mature into the sexually mature medusa form when conditions are just right.  Apparently one of the conditions that has to be just right is relatively warm water (about 77 degrees F or higher).  Oh, for those of you thinking of marine jellyfish and the serious stings that they can inflict; these freshwater jellyfish also have the nematocysts that “fire” stinging barbs into prey but apparently those nematocysts are too small to penetrate human skin.

What does this mean to fish and anglers?  Probably absolutely nothing.  But this is one of those interesting things you might observe while on the water.  We recently had another report of these freshwater jellyfish in a Platte valley sandpit and it is something curious that you would never expect in Nebraska waters.

4 Comments so far
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My parents were recently in Bancroft, Ontario in Canada at their cottage. They were shocked when my brother discovered a jellyfish in the freshwater lake. The jellyfish was the size of a quarter. They took a video. Is this normal?

Comment by Nicole

I guess that would depend on what you consider “normal”? The freshwater jellyfish that have been found in North American waters can be present all the time, but only occasionally are they observed, only occasionally are they present in the “classic” medusa form.

No, I am not surprised to hear your brother found a freshwater jellyfish in a natural lake in Canada. But then again I sure would not expect you to be able to go there and find those jellyfish all the time. It may be years before you see another one.

Daryl B.

Comment by whitetips

My boyfriend’s parents have a cottage on Baptiste Lake just outside of Bancroft, we found these little creatures this past Saturday Sept.11th, 2010 in 27 ft of water at the surface! We were baffled as we’ve never seen this in the lake before, and we are on the water ALLOT, and according to what the research says they may not be there next year! So I guess with the warm temps this year it was a perfect environment for them, we found them in the “classic” medusa form! we kinda knew it was a jellyfish but didn’t realize there were fresh water jellyfish! We are hoping that these little guys won’t be too negative on the aquatic plants or fish in the lake as many other invasive species are!

Comment by Tammy Thompson

I too saw these very recently! In fact, about half an hour North of Kingston, at Frontenac park. We were canoeing and I saw what appeared to be pale white shapes under the water, maybe the size of a nickel at most, and thought nothing of it, until one of them moved in that telltale manner! They weren’t clustered, spaced maybe 5-10 feet apart, but dozens of them!

I checked with my girlfriend’s mom (an avid diver) who explained what they were, and how rare they have been. Apparently they have the ability to sting, but cannot penetrate human skin due to their small size.

Either way, very cool. It must mean the water is healthy enough to support their delicate habitat, and for that I’m simply thankful.

Comment by W.

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