The surest way to prevent the huge, hungry carp from gaining a foothold in the lakes and threatening their $7 billion fishing industry is to sever the link between Lake Michigan and the Mississippi River basin, created by engineers in Chicago more than a century ago.
The strategy released by the Obama administration this week agrees only to conduct a long-range study of that idea, which could take years. The government also refuses to shut down two navigational locks on Chicago waterways that could provide an easy pathway for the carp into the lakes, although it promises to consider opening them less often.
Instead, the plan outlines two dozen other steps, from strengthening an electric barrier designed to block the carp's advance to using nets or poisons to nab fish that make it through. That's an expensive gamble that may not keep enough carp out of the lakes to prevent an infestation.
"We're spending close to $80 million just for a short-term deterrent," said Joel Brammeier, president of the Alliance for the Great Lakes, an environmental group. "We need to stop pushing money toward temporary solutions and get everyone on track toward investing in one that works for good - and that means absolute physical separation."
To be fair, the solution environmentalists prefer - cutting ties between the lakes and the Mississippi - would mean reconfiguring some 70 miles of canals and rivers. That's a massive undertaking that could not happen quickly and is fervently opposed by barge operators who move millions of tons of commodities through the Chicago locks each year.
Bighead and silver carp - both native to Asia - have been migrating toward the lakes since escaping from Deep South fish ponds and sewage treatment plants in the 1970s. The biggest can reach 100 pounds and 4 feet long, consuming up to 40 percent of their body weight daily in plankton, the base of the aquatic food chain. Once established in the lakes, the carp could starve out the prey fish on which popular species such as salmon and whitefish depend.
The carp have already infested parts of the Mississippi and Illinois rivers, driving away many native fish. Silver carp are known to hurtle from the water at the sound of passing motors and slam into boaters with bone-breaking force.
While scientists differ on whether the carp would thrive in the Great Lakes, which are colder, deeper and ecologically different than rivers, many say the risk is too great to take any chances.
"None of us know for certain what their impact would be," University of Notre Dame biologist David Lodge told a House subcommittee this week. "There's only one way to find out, and I don't think any of us want that."
Pulled in different directions by the fishing and the barge industries, and politicians in Illinois and those from the other Great Lakes states, the Obama administration says the only realistic approach is to confront the carp on multiple fronts instead of taking the bolder step of severing Lake Michigan from the Mississippi basin.
"We cannot fight biology with engineering alone," Cameron Davis, the Environmental Protection Agency's spokesman on the issue, told the congressional panel.
Yet the federal plan is heavy on technological innovations. Among them: barriers using sound, strobe lights and bubble curtains to repel carp and biological controls to prevent them from reproducing. They're promising measures - but still on the drawing board.
Environmentalists and Great Lakes governors outside of Illinois who want to close the Chicago locks claim it's the best short-term option. But it isn't a foolproof solution, as young carp might still be able to slip through the leaky structures. The Chicago waterways also have other access points to Lake Michigan.
Army Corps of Engineers officials are putting their faith in a two-tiered electric barrier in the Chicago Sanitary and Ship Canal about 25 miles from Lake Michigan, to which they will add a third section this year. It emits pulses to scare off the carp or knock them unconscious if they don't turn back. No carp have been found above the barrier, although biologists have detected their DNA in numerous spots past it and even within the lake itself.
"While we're all talking," Lodge said, "the fish are swimming."
That almost certainly means at least some carp have eluded the device and reached the lake. The government's plan aims to keep their number low enough to prevent them from breeding. The problem is that no one knows how many carp need to make it into the lake to establish a foothold that can't be turned back.
"This is a lot of money to pile into stopgap measures," said Phil Moy, a University of Wisconsin Sea Grant researcher. "It may do some good in the short term, but in the long term it's not going to solve the problem of invasive species on both sides of the divide. Ecological separation has to happen for this to be successful."