The wolf is at the door of the Great Lakes ecosystem once again. The wolf comes in the form of a fish: Huge Asian carp have been found in the Illinois River; which connects the Mississippi River to Lake Michigan. Two species of Asian carp – the bighead and silver – have crowded out valuable native fish species and now account for 90% of the fish population in parts of the Illinois River. Asian carp are now at the threshold of the Lake Michigan where they could devastate an already stressed native ecosystem and ravage a multi-billion dollar commercial and sports fishery.
Asian Carp Escaped From Fish Farms During Floods
Bighead and silver carp were imported by Arkansas catfish farmers in the 1970’s to keep their ponds clean by eating algae and other suspended matter. The introduction of Asian carp into the Mississippi River basin is a lesson in the unintended consequences of importing non-native species.
Ponds in many catfish farms overflowed their banks during large floods in the early 1990’s. With the flooding, Asian carp were released into local rivers and streams and steadily worked their way up the Mississippi River ever since, becoming the dominant species in some parts of the river basin, particularly the Missouri and Illinois Rivers.
Boaters and water-skiers have been injured by silver carp that have a habit of jumping high out of the water at the sound of approaching boat engines.
Now they are on the verge of infiltrating the Great Lakes.
Why Asian Carp Are a Threat to the Great Lakes Ecosystem
The Great Lakes ecosystem is already home to 180 non-native species, including the sea lamprey, zebra mussels, and round goby; many of which were introduced to the lakes in ballast water discharged by trans-Atlantic freighters. Many experts believe the induction of Asian carp into the Great Lakes would be a devastating blow to the fragile ecosystem.
Asian carp are a threat to the Lake Michigan and the other Great Lakes because of their size, appetite, and prolific reproductive capacity. Silver carp can grow to 40 lbs, and bighead carp can weigh over 100lbs. and reach a length of 4 ft. Thankfully the bighead carp are not known to jump out of the water.
These fish consume vast amounts of food (up to 20% of their body weight) per day and females can produce a million eggs at one time. Though Asian carp are not predators (they are filter-feeders who consume primarily plankton and algae), many environmental authorities fear that if they establish themselves in the Great Lakes and their tributaries, they will wipe out the lower end of the food chain, thus wreaking havoc on the ecosystem.
Silver and bighead carp are well suited to the temperate fresh water and climate of the Great Lakes region which is similar to their native habitat.
Controlling Asian Carp
The only connection between the Mississippi River System (including the Illinois River) and the Great Lakes is the Chicago Sanitary and Ship Canal. The US Army Corps of Engineers, the EPA, the State of Illinois, and others are working together to install and maintain a permanent electronic barrier in the canal about 30 miles downstream from Chicago. The barrier sends a small electrical current through the water to repel the carp, but leaves the waterway open to free passage by ships. Authorities are confident that this electronic “fence” combined with other alternative strategies (such as bubble and acoustic barriers) will be successful in turning Asian carp away from the Lake Michigan and the other Great Lakes.
Others do not share that confidence. The system is far from fool proof and many believe the only way to keep Asian Carp from reaching the Great Lakes is to close the locks on the Chicago canal; effectively sealing the water route from the Mississippi to Lake Michigan. The problem with this strategy is that it would also close off shipping lanes, and Illinois business interests have lobbied hard against closing the locks.
Attorneys General from Michigan, Ohio, Pennsylvania, Minnesota, and Wisconsin have filed a suit in federal court to force the closure of the locks.
For now, biologists and economists in the five states are crossing their fingers and hoping the electronic barrier holds
Bryan Walsh, “Lake Invaders”, Time Magazine