There was a big deal around here a few years ago about "walking catfish" or "snake head fish" or some shit like that. People would have them as pets and then get sick of them and release them into lakes, streams, or ponds, but those fish are able to travel over short distances of land and they were spreading and killing off fish that are supposed to be here.
I think it's illegal to own one of those here now.
Then there's this whole fiasco.....
Asian Carp and the Great Lakes
Asian carp have been found in the Illinois River, which connects the Mississippi River to Lake Michigan. Due to their large size and rapid rate of reproduction, these fish could pose a significant risk to the Great Lakes Ecosystem.
To prevent the carp from entering the Great Lakes, the U.S. Army Corps of Engineers, U.S. EPA, the State of Illinois, the International Joint Commission, the Great Lakes Fishery Commission, and the U.S. Fish and Wildlife Service are working together to install and maintain a permanent electric barrier between the fish and Lake Michigan.
How did Asian carp get so close to the Great Lakes?
Two species of Asian carp -- the bighead and silver -- were imported by catfish farmers in the 1970's to remove algae and suspended matter out of their ponds. During large floods in the early 1990s, many of the catfish farm ponds overflowed their banks, and the Asian carp were released into local waterways in the Mississippi River basin.
The carp have steadily made their way northward up the Mississippi, becoming the most abundant species in some areas of the River. They out-compete native fish, and have caused severe hardship to the people who fish there.
Chicago Area waterways map showing location of carp barrier (Illustration courtesy of Phil Moy, University of Wisconsin Sea Grant Institute)
The Chicago Sanitary and Ship Canal, where the barrier is being constructed, connects the Mississippi River to the Great Lakes via the Illinois River. Recent monitoring shows the carp to be in the Illinois River within 50 miles of Lake Michigan.
What effects might Asian carp have on the Great Lakes?
Asian Carp are a significant threat to the Great Lakes because they are large, extremely prolific, and consume vast amounts of food. They can weigh up to 100 pounds, and can grow to a length of more than four feet. They are well-suited to the climate of the Great Lakes region, which is similar to their native Asian habitats.
Researchers expect that Asian carp would disrupt the food chain that supports the native fish of the Great Lakes. Due to their large size, ravenous appetites, and rapid rate of reproduction, these fish could pose a significant risk to the Great Lakes Ecosystem. Eventually, they could become a dominant species in the Great Lakes
http://www.epa.gov/glnpo/invasive/asiancarp/
