Shrimp species latest Great Lakes invader

Researchers at McGill University in Montreal had predicted the bright orange Hemimysis anomala would be added to the list of Caspian Sea invaders, if action was not taken to stop the discharge of contaminated ballast from freighters plying the St. Lawrence Seaway, the Milwaukee Journal-Sentinel said.

In November, the shrimp showed up near Muskegon, Mich.

Anthony Ricciardi, one of McGill scientists, called it a sign of an "ecological takeover" of the Great Lakes.

The shrimp feed on zooplankton and phytoplankton that sustain Great Lakes native fish species, said David Reid, a National Oceanic and Atmospheric Administration scientist.

Great Lakes-bound overseas freighters are required to exchange ballast water mid-ocean to kill freshwater organisms with salty water, the Journal-Sentinel said. But about 90 percent of overseas freighters arrive in the Great Lakes laden with cargo, and have historically been exempt from the exchange law.

Reid says there is a bright spot. The Canadian government requires overseas ships to flush empty ballast tanks with saltwater before entering the seaway. Early studies show that is an effective means of killing unwanted critters.

Copyright 2006 by United Press International