Monica Davey, New York Times 12 Dec 09;
CHICAGO — Alarms are sounding near the edge of the Great Lakes. Genetic evidence of Asian carp — a mammoth, voracious, non-native conqueror among fish, long established in the Mississippi River — has turned up just a few miles from Lake Michigan in the waterway that links the river system to the lake. If such creatures were to swim on into Lake Michigan, some scientists say they fear the fish would ultimately upend the entire ecosystem in the lakes that make up a fifth of the earth’s fresh surface water.
So an urgent search is underway in Chicago for sightings of the silvery-gray fish with low-set eyes, the sort that even a scientist here described, somewhat unscientifically, as “an exceedingly ugly fish.” Advocates for the lakes are demanding emergency closures of a lock to block their arrival. And the attorney general of Michigan says he will sue to stop the fish.
Forgotten in all the fuss now is that these bighead and silver carp — imported in the 1970s to scarf up algae from ponds in the Deep South — are apparently making their way north to the Great Lakes along a route that humans, not nature, dreamed up.
Over a century ago, people built a canal to link the Great Lakes to the Mississippi River system. Historians say early travelers reported they could make their way from the lakes to the river by canoe in the wet season, but faced a portage during dryer periods; hence, the call for a canal. Over the years, it carried fetid sewage away from Chicago and Lake Michigan as part of a remarkable engineering feat that reversed the flow of the Chicago River. Commercial barges traveled up and down the vast, crucial path.
Along the same path came the carp, who had escaped from their southern ponds and spread through the Mississippi River system, by some accounts, thanks to flooding in the 1990s. Scientists have worried for years about the capability of an assortment of other non-native species (the round goby, the zebra mussel) to make their way either north from the Mississippi River system into the Great Lakes or back south on an opposite journey.
“The bottom line is that this canal is a conduit — a highway to environmental havoc — from one of these important watersheds to the other,” said David M. Lodge, a biologist and the director of the center for aquatic conservation at the University of Notre Dame.
It has surely happened before. Dams, levees, flood diversion projects. We redirect water and solve a problem, only to discover some new, unintended consequence.
In California and Oregon, some blame four old dams, which certainly generated electricity, for a decline in salmon in the Klamath River. In Missouri, during flooding along the Mississippi a year ago, residents of towns with low, primitive levees begrudged neighbors with enormous ones, saying the higher walls were directing unnatural amounts of water their way.
In the end, it seems, nature does as it wishes, try as we might to keep the waters in our grasp. For more than a decade, as reports of escaped northbound Asian carp emerged from parts of the Mississippi, civic, environmental and business leaders around the Great Lakes fretted. Asian carp committees were formed, reports were written, and more than $20 million was spent to build elaborate electric fences in the Chicago Sanitary and Ship Canal to at least temporarily hold back the carp from Lake Michigan, a measure one expert likened to hand-washing in the face of the H1N1 flu — wise but not a cure. And even as a third electric barrier is under construction, the authorities have reported finding the genetic evidence of the carp beyond the fences, within about six miles of Lake Michigan.
Some here now say that the only guaranteed, permanent way to keep these fish from the Great Lakes may be to put things back where we found them: separate the lakes from the Mississippi River watershed.
Needless to say, the politics, engineering and costs of such a solution could not be more tangled. People, of course, are used to what they built. Interests fight interests, and any one of them can draw an environmental arrow from the quiver. Those opposed to unbuilding the canal, including a barge industry that hauls 16.9 million tons of sand, coal, gravel, cement and salt through it, envision an extraordinary price for overhauling Chicago’s water system and assert that 1.3 million more trucks would be needed each year to handle what the barges carry.
“What is that going to do from an air pollution standpoint?” said Lynn M. Muench of the American Waterways Operators, a trade group that includes barges. “This is a huge environmental issue.”
So are the carp. Despite tests that found Asian carp DNA in the water, no actual silver or bighead carp have been spotted as close to the lake (a recent strategic poisoning turned up one, but farther away), and some here view that as proof that this is a lot of worry about nothing. Maybe a carp fell out of a bait box? Maybe it slipped through some other passage during flooding?
Still, those who know carp best say even a whiff of them is much to worry about, especially for the Great Lakes’ $7-billion-a-year fishing industry. The carp can weigh as much as 100 pounds, and the silver carp has a habit of jumping, seeming to challenge boaters as much as it does other fish. They eat pretty much all the time, vacuuming up the plankton that other fish depend on and crowding the others out.
Then again, most scientists admit they do not know exactly how the Asian carp would behave in the Great Lakes. Though a few have been reported in Lake Erie in the past, biologists have mainly dismissed the discoveries as isolated, and say they leave little precedent for what might happen in such large bodies of water.
Already in these lake waters are the zebra and quagga mussels, more unwanted non-native species. They have devoured plankton throughout the lakes, harming native species that need it too. The mussels are thought to have arrived here in the ballast water of international trade ships, one more unintended consequence.
“It is conceivable that given how much the zebra and quagga mussels have eaten up already, there may not be much left for the Asian carp, and they might struggle to thrive,” Reuben R. Goforth, an assistant professor of aquatic community ecology at Purdue University, offered hopefully.
