Asian Carp in Illinois
A century ago the Chicago Sanitary and Ship Canal was hailed as an engineering masterpiece. Built a century ago to carry sewage and ships, the canal connects the Great Lakes basin to the Mississippi River Valley – two ecosystems that evolved separately for millennia. But today the canal has become a superhighway that allows plants and animals from one ecosystem to invade the other. Zebra mussels from Lake Michigan have spread through the Mississippi River and her tributaries, clogging water pipes and causing millions of dollars worth of damage to industrial facilities. There are many other examples. Today two species of Asian carp threaten to devastate the Great Lakes and inflict irreversible damage on sport fisheries, wildlife, regional economies and the people that rely upon them.
Asian carp are voracious plankton feeders that can quickly dominate aquatic ecosystems by gobbling up the same food that sustains native fish populations. They are already dominating the Illinois River, where they grow so large they have no natural predators. They are rapidly approaching the Great Lakes, which have already been weakened by other invasive species. The threat is serious: plankton is the foundation of the Great Lakes food web.
Bighead carp grow to more than 4 feet long and weigh up to 100 pounds. Silver carp leap when disturbed and injure river users. Cuts, bruises, and broken bones have been reported from silver carp collisions along the Illinois River.
If Asian carp invade the Great Lakes, they could also devastate the region’s $7 billion fishing industry and permanently alter how recreational boaters, anglers and tourists use and enjoy the lakes and their many tributaries. They are already overtaking and out-competing native fish in the Mississippi and Illinois Rivers. Many US and Canadian rivers feeding the Great Lakes could also be at risk, as shown on the map for a few adjacent states.
Connecting the Great Lakes to the Mississippi River system seemed like a good idea at the time. By the 1890’s Chicago’s sewage, dumping into the Chicago River and draining naturally into Lake Michigan, was beginning to pollute its drinking water supply. By digging the canal, the State of Illinois caused the Chicago River to reverse direction, allowing Lake Michigan to serve as a giant toilet tank flushing sewage into the Illinois River and on to the Mississippi River.
Today, of course, we have options available to us that weren’t available a hundred years ago. Most other cities around Great Lakes employ modern sewage treatment technologies that allow them to dump treated sewage into the Great Lakes without poisoning their drinking water. And our extensive networks of railroads and highways provide viable alternatives to waterborne commerce within the Chicago metropolitan area.
The obvious long term solution is to permanently close the connection between the Great Lakes and the Mississippi River basin to prevent invasions in either direction via the canals. Four possible locations for such a barrier have already been identified (see Alliance for the Great Lakes report here). Unfortunately, state and federal agencies have spent most of their time and effort on stopgap measures that have failed to stop the steady movement of Asian carp.