From the Stevens Point Journal:
WAUPACA – A relatively rare species of invasive freshwater jellyfish has been confirmed to be living in a Waupaca County lake, the Golden Sands Resource Conservation & Development Council said Tuesday. A resident reported the unusual animals at Spencer Lake last week and Paul Skawinski, an invasive species expert from Stevens Point, visited the lake and confirmed the report, the council said. The council is a conservation organization that works in several central Wisconsin counties.
The jellyfish are about the size of a penny and originate in China; they first were observed in Wisconsin in the late 1960s and are believed to have arrived by clinging to aquatic plants that were imported for water gardens or aquarium use, and later escaped to the wild during flooding events or through illegal dumping of aquarium water or plants. A total of 94 Wisconsin water bodies are currently known to contain freshwater jellyfish, the council said.
Freshwater jellyfish haven’t been studied enough to determine their impact on Wisconsin’s ecosystems. They feed on zooplankton, the same food source of young fish, so they may affect fish populations. According to Skawinski, the jellyfish do contain stinging cells on their tentacles as saltwater jellyfish do, but the cells are harmless to humans.
“Their stinging cells are only effective against small creatures like plankton. They are too small to pierce human skin, so they pose no threat to swimmers or other lake users,” he said.
Anyone who observes freshwater jellyfish or another aquatic invasive species is asked to contact Golden Sands RC&D Council at 715-343-6215, or firstname.lastname@example.org.