The hot, steamy days of late summer can provide the perfect conditions for one of our favorite rare, strange-but-true aquatic oddities: freshwater jellyfish. Native to China, Craspedacusta sowerbii has been found on every continent other than Antarctica—including here in Georgia! They can appear suddenly in warm waters where they had never been seen before.
Concern or Curiosity?
Despite their often-alarming numbers, they are harmless to most things except for the plankton they eat. Although they are not true jellyfish, they do have stinging cells. Fortunately for us, their stingers can’t penetrate human skin. They often disappear as suddenly and mysteriously as they appeared.
Before becoming medusa, the free-swimming “jellyfish” stage, they are sessile polyps resembling anemones, or their distant cousins the freshwater hydra. The polyps attach to rocks and debris and can remain undisturbed and undetected until conditions change, and they suddenly transform into medusa. What makes them change is not fully understood. How they have managed to spread around the world is also something of a mystery. They may be carried as polyps by birds on their feet or carried debris, as well as washed downstream.
Lake Management Experts
Like many other lake oddities, freshwater jellyfish are some of the situations Aquascape Environmental gets calls to assess. Having licensed and credentialed aquatic biologists and professionals on our team, we can assess and maintain your lakes to maximize the enjoyment of users and health of the lake’s fish and animal population.
Observational evidence suggests that freshwater jellyfish are most likely to be found in calm, man-made impoundments and reservoirs and in water temperatures of 80°F and above. Freshwater jellyfish tend to swim just below the surface of the water, especially on sunny days. Large groups (jellyfish “blooms”) have been known to pop up, making for a startling sight. Be on the lookout for the extraordinary freshwater jellyfish in a lake near you!
Check out this video of a close encounter with a freshwater jellyfish:
