Jellyfish
Freshwater Jellyfish
Craspedacusta sowerbii
These illustrations are AI-generated, not photographs, and are not to scale. They show what to look for; they are not a substitute for an expert identification.
How to identify it
Size: About the size of a dime to a quarter: 5 to 25 millimeters (up to about 1 inch) across.
- A small, nearly clear bell with a milky white or greenish tint.
- Four canals inside the bell that form a cross.
- A feeding tube hanging down from the center.
- A fringe of many short tentacles around the edge, with four longer ones.
- Usually seen in late summer in calm, warm water, and in some years not at all.
Don’t confuse it with
It is the only freshwater jellyfish you are likely to see in Michigan, so a small jellyfish in an inland lake is almost certainly this one.
Harmless to people.
Where it came from
Native to the Yangtze River basin in China.
Found in North America since the late 1800s, probably carried with shipments of aquatic plants or fish. Its tiny bottom-dwelling stage is easy to move without anyone noticing.
Earliest dated Michigan record: 1933, the Huron River near Ann Arbor. This is the oldest dated record in the USGS non-native species database, not necessarily when it first arrived.
Why it matters
It is considered harmless to people: its stings are too weak to be felt. It eats tiny animals called zooplankton, and scientists are still studying its effect on lakes. It is included here because people often spot it and wonder what it is.
Michigan law
Not on Michigan's list of prohibited or restricted species. The boating and bait rules below still apply to everyone.
If you find it
- Don’t move it. Michigan law requires boaters to remove all aquatic plants from boats, equipment and trailers before launching. Before trailering, you must pull all drain plugs, drain live wells and bilges, and make sure the boat and trailer are free of aquatic plants and animals. What the law requires
- Never release bait. Releasing baitfish into Michigan waters is illegal. Put unused bait in the trash, never in the water.
- Report it. Take a photo, note where you saw it, and report it to the Midwest Invasive Species Information Network (MISIN) or through Michigan’s invasive species program. Experts there can confirm what you found.
- Ask before removing or treating. Treating a lake with herbicides or other chemicals needs a state permit, and some removal work does too. Start with the state’s Aquatic Nuisance Control program before taking action.
Michigan lakes where it has been recorded
78 Michigan lakes on this site have a record of this species.
Allegan
Antrim
Barry
Clear Lake, Cloverdale Lake, Gun Lake, Hall Lake, Little Long Lake, Otis Lake, Pine Lake, Wall Lake
Branch
Calhoun
Cheboygan
Clare
Crawford
Grand Traverse
Hillsdale
Iron
Jackson
Kalamazoo
Lake
Lapeer
Livingston
Manistee
Mason
Mecosta
Montcalm
Newaygo
Oakland
Osceola
St. Joseph
Van Buren
Washtenaw
Wexford
A lake that is not listed may still have it. Records exist only where someone found the species and reported it, so “not recorded” does not mean “not present.”
Lake records: Midwest Glacial Lakes Partnership Conservation Planner; underlying records from the USGS Nonindigenous Aquatic Species database.
Sources
Earliest dated record: USGS Nonindigenous Aquatic Species database.