Native to eastern Asia, the parasitic copepod (a type of zooplankton, small aquatic animals) Neoergasilus japonicus was first collected by Great Lakes Science Center scientists in 1994 in Saginaw Bay in Lake Huron. The copepod was found on four fish species at that time; fathead minnow, largemouth bass, pumpkinseed sunfish, and yellow perch. Concurrent sampling in Lakes Michigan and Superior showed no infection. Further sampling in Saginaw Bay in 2001 revealed infections in 7 additional species; bluegill, carp, channel catfish, goldfish, green sunfish, rock bass and smallmouth bass. The copepod was found attached primarily to the dorsal fin, but also to the anal, tail, pelvic and pectoral fins, picture 1 above shows the grasping teeth with which they attach and picture 2 is a typical dorsal fin of an infected fish.

It is believed that this new species to the Great Lakes was introduced on exotic fish for the aquaculture industry. This invasive copepod spread rapidly through Europe in the 60's and 70's and is spreading through North America currently, some specimens showing up in Alabama in the mid-90's.

Great Lakes Copepod Key