New Water Flea Quickly Spreads to Lake Michigan

 

A catchy new aquatic nuisance species has already made its way to Lake Michigan after making its first Great Lakes appearance in Lake Ontario only a year ago.

Known as the fishhook water flea, it is a crustacean about one centimeter long that closely resembles the spiny water flea (Bythotrephes cederstroemi).  However, its barbed tail is considerably longer and has a loop at the end.  Its formal name is Cercopagis pengoi.

Phil Moy, UW Sea Grant Fisheries Specialist, says the effects this latest invasive species will have on the food chain of Lake Michigan are not yet known, but they will probably be similar to those of the spiny water flea.

"It's a very similar animal," Moy said.  "It comes from the same area as the spiny water flea, the Baltic Sea, and will probably affect the food chain in the same way.  But it's too early to know exactly how either species will ultimately change things."

Moy said Cercopagis will compete with newly hatched fish for zooplankton, tiny floating animals near the bottom of the food web.  This may leave fewer zooplankton for young yellow perch and other sport fish. 

The tiny cladoceran was first discovered in Lake Ontario in July, 1998, and its advance through the lakes has been unusually rapid.

"We predicted that this would spread to other lakes, but quite honestly I'm astounded at just how quickly these invasions have occurred," said Hugh MacIsaac, a biologist at the University of Windsor who is researching the animal's introduction into the Great Lakes.

The cladoceran probably hitched a ride to the Great Lakes in the ballast water of ships traveling from eastern Europe.  Another freighter probably carried it from Lake Ontario to Lake Michigan’s Grand Traverse Bay where it was recently found last summer by Tom Kelly of the Inland Seas Association in Suttons Bay, Mich.

In mid-September, a commercial fisherman near Waukegan, Ill., found gobs of the creatures on his fishing lines. MacIsaac said that's also been happening in Lake Ontario, and fishermen are unhappy about it.

"When fishermen pull up their lines, their lines will be caked with small globs or balls of these animals. And it actually makes it quite difficult to reel the fishing lines in so people have complained about it for that reason," MacIsaac said.

Cercopagis has not yet been identified in Wisconsin waters of Lake Michigan.  Its eventual arrival is likely, Moy said, but south-flowing currents along Wisconsin's Lake Michigan shore should hinder its advance from the Waukegan area.

MacIsaac says fishermen can easily spread the critters from lake to lake if they're not careful. Cercopagis can attach itself to fishing lines and harbor eggs that can hatch the next time they hit water—even if that’s a couple of weeks later. Cleaning off boats and equipment after each use is a good way to prevent Cercopagis from spreading. And MacIsaac says it's also important not to take on water from one lake and empty it into another.

If you find Cercopagis in Wisconsin waters of Lake Michigan, please email UW Fisheries Specialist Phil Moy or call him at (920) 683-4697.

More information on Cercopagis pengoi can be found at the following web sites:

Sea Grant Non-indigenous Species Web site (sgnis)

Article from Milwaukee Journal Sentinel, November 3, 1999

The Great Lakes National Program Office of the Environmental Protection Agency

Hugh MacIsaac's Cercopagis pengoi page

 

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Last updated 28 March 2000 by Karl
All contents copyright 1999 University of Wisconsin Sea Grant Institute

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