Fears that giant, voracious species of carp will get into the Great Lakes and wipe out other fish have led to rising demands that the government close the waterway connecting the lakes to the Mississippi River — an unprecedented step that could disrupt the movement of millions of tons of iron ore, coal, grain and other goods.

The dispute could become an epic clash of competing interests: commerce, environmentalists and fishermen.

Michigan Gov. Jennifer Granholm and five environmental groups threatened Wednesday to sue the U.S. Army Corps of Engineers to force it to temporarily shut three shipping locks near Chicago because of evidence that Asian carp may have breached the electrical barrier that is supposed to hold them back from the lakes.

Environmentalists fear the fish, which consume up to 40 percent of their body weight daily in plankton, could starve out smaller and less aggressive competitors and cause the collapse of the $7 billion-a-year Great Lakes sport and commercial fishing industry.

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