Kathy Potocsnak called me recently about a mystery organism that she'd found near her boat dock on Smith Lake. Since I couldn't recognize it from a verbal description, she brought one to the office. I made some photos and sent them to Rusty Wright, Extension Fisheries Specialist. Here's his response:"Yep that is a freshwater jellyfish. I usually get 1-2 calls a year confirming the presence of these critters in our lakes and ponds. I think many times I'm settling a bet!
"Freshwater jellyfish, Craspedacusta sowerbyi, is a non-native species originally from Asia. It is now common virtually globally. They eat small zooplankton but there is no evidence that they do any damage to our ecosystems. People see them most often from clear lakes, pools, and reservoirs: however they are also in more cloudy turbid water as well it is just that we can't see them as well in those systems.
"It is an interesting critter!"
Here's a link to the U. S. Geological Survey's web page about these jellyfish.
This jellyfish was actively swimming around in the jar. It would swim through the water for a few seconds, then it would pause and just float. After I made these photos, Kathy took the jellyfish back to the lake.
Thanks to Rusty for the identification of the photos, and to Kathy for bringing the freshwater jellyfish to our office.
5 comments:
Their back. Glad to know what they are. Paddleboarding yesterday evening around 6pm,glided through about 1/4 mile of water filled with them at depths of approx. 4" to 18". This was about 1 mile up from the damn going back towards Big Bridge on Dr. Harris Spring Branch. First time I've seen anything like them in the 13 years I've lived on the lake.
Thanks for that report on your siting.
Will they sting?
According to the publication mentioned in the blog post, "Freshwater jellyfish is not considered dangerous to humans. Although its stings can paralyze macroinvertebrates and small fish, its small nematocysts are not likely to penetrate human skin."
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