Freshwater Jellyfish

Freshwater Jellyfish

Freshwater jellyfish, Craspedacusta sowerbyi, are sometimes found in high quality static waters of Alabama.  Both the medusa (moving) and the polyp or hydroid (fixed) stage are found.  The medusa stage is most often seen in the late summer through fall.  Small by marine jellyfish standards, freshwater jellyfish in the medusa stage usually have a diameter smaller than one-inch (22 mm).  The polyp stage is even smaller, from a tenth-inch to third-inch (2 mm to 8 mm).  The Joe and Torie Champion of Commercial Diving of Alabama in Wetumpka filmed freshwater jellyfish swimming at Lake Martin near Chimney Rock.  The Fisheries Section appreciates them letting us use this video for your enjoyment.

The stings of freshwater jellyfish are not strong enough to be felt by humans.  Freshwater jellyfish eat copepods and other tiny invertebrates in the water column.  Crayfish may be one of the few predators that medusa stage freshwater jellyfish have.