Freshwater Jellyfish Found In St. Lawrence

A freshwater oddity has been spotted in the St. Lawrence River and Lake Ontario.

The diminutive freshwater jellyfish are making appearances in the river as well as the eastern basin of Lake Ontario, according to Rodger M. Klindt, aquatic biologist with the state Department of Environmental Conservation (DEC) in Watertown.

"Freshwater jellyfish are abound in the St. Lawrence River," said Mr. Klindt.

While the creatures are not uncommon in the river and lake, they are seldom noticed except when river and lake temperatures rise.

"They will only develop during certain environmental conditions," he said. Those conditions include warm water temperature. It's a phenomena that isn't unheard of.

"Under the extreme environmental conditions, we will start getting phone calls," said Mr. Klindt.

He said that the species are small, growing to be only an "inch across at best," unlike their saltwater dwelling relatives.

"They are quite small. A lot people could overlook them if the lighting is quite right," said Mr. Klindt. Due to their size, they are species that are not often seen. It isn't until they develop into the "Medusa-stage" with the tentacles that they become noticed.

DEC has received reports of the species in several inland bodies of water in the past, including Sylvia Lake in St. Lawrence County and several waters in the Indian River Lake System.

This summer, jellyfish have been reported near Grindstone Island, Chaumont Bay and Wellesly Island as well, according to Mr. Klindt.

Mr. Klindt said that as far as he knows, the jellyfish do not pose any harm to swimmers or river users, adding that their stings are quite harmless because of their small size.

The jellyfish feed on extremely small organisms living in the river and lake system.

"As far as I know, they are just going to be feeding on zooplankton," he said.