The grass carp is the lawn mower of the aquatic world. This Asian fish can eat as much as three times its weight in submerged plants every day, and it’s not exactly a delicate fish – large grass carp can weigh hundreds of pounds.

Now, a legislator has introduced a bill proposing that this fish be imported to Maine.

Ronald Usher, D-Westbrook, believes that grass carp can be used in Maine, as they are in dozens of other states, to control the growth of invasive aquatic plants like milfoil that can drastically reduce property values for lakeside homes.

Though no state agency has taken a formal position on Usher’s bill yet, the idea has several state scientists very concerned.

Though the grass carp eats milfoil, it also eats every native plant, right down to the roots, said Paul Gregory, an invasive aquatic plant specialist for the Maine Department of Environmental protection.

“It’s a cow with gills,” he said. “You have to decide to eliminate all the plants in a body of water.”

In some extreme cases of overpopulation, grass carp have literally sterilized ponds, eating everything from leaves to roots to the organic matter in the soil that makes plant growth possible, Gregory said.

Usher’s bill, LD 1646, would call for a two-year test with just a few sterilized grass carp to find out how effective the fish would be on the variable-leaf milfoil that is known to have infested 11 Maine lakes and ponds. The test would be run under the control of the Department of Inland Fisheries and Wildlife and would be subject to constant monitoring, according to the bill.

Other states including Washington, Oregon and Texas regularly use these sterile fish to control problems with invasive plants and have been pleased with the results, according to wildlife officials in those states. The state of Arizona even uses grass carp to keep canals and drinking-water reservoirs cleared of vegetation.

The grass carp, also known as the white amur, is a native of Asia, where it evolved side by side with Eurasian milfoil. It was imported into the United States 25 years ago to be used as a biological control mechanism for milfoil in southern catfish ponds. The grass carp escaped into the Mississippi River, however, and is now found throughout the Midwest – including in several of the Great Lakes.

There is almost universal agreement that an uncontrolled grass carp population can be disastrous. They are difficult to catch, and control mechanisms such as electric barriers and poison have failed. An early introduction in Texas destroyed bass fishing in one pond because the carp ate all the plants that bass need for feeding and shelter.

Texas now allows only the sterilized carp, which one scientist there estimates have a one-in-2.5 million chance of reproducing.

Other biologists raise questions about the reliability of the sterilization procedure, which involves altering the fish’s chromosomes. The sterilization is just shy of 100 percent effective.

“All it takes is two [fish],” Gregory said.

Peter Bourque, director of fishery program development at DIF&W, is also concerned that a grass carp program could get out of control.

Even if the grass carp can’t breed, the state has long struggled with so-called “bucket biologists” who introduce nonnative fish into ponds where they don’t belong, he said.

The carp could destroy the native vegetation that many sport fish rely on. Trout and salmon eat insects that hide in aquatic plants, and some species also hide from predators in the vegetation when they first hatch. Ducks, too, need the native plants that grass carp destroy, Bourque said.

“It seems like it just upsets the ecosystem enough to prove disastrous for all the native flora and fauna,” he said.

Gregory worries that a grass carp introduction could backfire. A pond stripped of its native plants is the perfect environment for an invasive plant to colonize, he said.

Last year, when faced with the state’s first discovery of a fast-growing invasive plant called hydrilla in Pickerel Pond in Limerick, the Department of Environmental Protection chose to use pesticides over grass carp because of a fear that fish could not be controlled, he said.

“We need to preserve the environmental integrity of a body of water, not deliver answers that are as harmful as the problem itself,” Gregory said.

Usher’s bill has been referred to the Legislature’s Committee on Inland Fisheries and Wildlife, but has not yet been scheduled for a public hearing.