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By Jennifer Bieman, The London Free Press

Step aside zebra mussels and phragmites, another foreign invader is lurking beneath the surface of Southwestern Ontario’s lakes and streams — a little umbrella-shaped creature that’s making people who see it do a double take.

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They’re freshwater jellyfish, a non-native species that’s been spotted in Port Dover, Norfolk County, Welland, Fort Erie and in lakes and streams across central Ontario. Though the small and slimy translucent animals are a rare sight, one thing is clear: they’re here to stay.

“There’s no known way to remove freshwater jellyfish from a lake ecosystem once it is there,” said Jeff Brinsmead, senior invasive species biologist with the Ministry of Natural Resources and Forestry.

The ministry believes the jellyfish, whose proper name is Craspedacusta sowerbii, were stowaways on aquatic plants imported to Europe in the 1800s before they hitched a ride to Philadelphia in boat ballast water. Brinsmead said the jellyfish likely arrived in Ontario on a contaminated ship or plant. The invasive invertebrates, native to the Yangtze River in China, were first discovered in Georgian Bay in the 1950s and inland at Lake Muskoka in 2002.

“In both cases they were probably there for some time before they were reported,” Brinsmead said.

Though Muskoka is a hot spot for the 2.5-centimetre creatures, the ministry said freshwater jellyfish appear to have entered lakes Erie and St. Clair, they’re just not spotted often.

Darien Donnelly and Jeremy Stevenson didn’t know what to make of the translucent blob floating in the water near their fishing dock by Port Dover’s lift bridge July 8. They thought it was a piece of garbage, until it moved.