Carp and the Lakes
December 28, 2009
Unwelcome species don’t get much more unwelcome than Asian bighead and silver carp, which were imported to Southern fish farms in the 1970’s, escaped into the Mississippi system and have spent a decade or more moving slowly upriver toward the Great Lakes.
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The fish are fertile and voracious, crowding out native species by vacuuming up algae and plankton. They are also bizarrely dangerous to boaters, erupting from the water like self-hurling bricks.
Ever since the fish started heading north, ecologists have warned about the devastation that awaits if they get loose in the Great Lakes, unchecked by natural predators and muscling out every competing species. It is not just the lakes’ $7 billion fishing industry that could be blighted by carp, it’s the entire ecosystem, already badly compromised by other invasive species and pollution.
The watery path that could seal the Great Lakes’ doom is the Chicago Sanitary and Ship Canal, which links the Mississippi River system to the Great Lakes. Electrified underwater barriers erected by the United States Army Corps of Engineers in the canal may already have failed; carp DNA has been detected on the wrong side of the fences.
The federal Environmental Protection Agency is spending a modest $13 million to tighten the canal’s defenses, by shoring up low-lying land beside the canal and nearby carp-infested waterways so the carp can’t ride floodwaters past barricades and into Lake Michigan. In a case that has just reached the United States Supreme Court, Michigan is suing Illinois and the Army Corps to force the closing of two canal locks that give a direct route into the lake.
The only sure way to stop carp — and whatever other invasive species are waiting — is to close the canal and again separate the Mississippi and Great Lakes watersheds. That would be hugely costly and politically difficult, given the importance of shipping to the region.