DNA from invasive silver carp has been found in the Mississippi River above the Coon Rapids Dam, raising the alarming prospect that the dreaded leaping fish may already be on its way to Mille Lacs and other popular recreational lakes in Minnesota.

Natural Resources Commissioner Tom Landwehr said on Thursday that the test results will force the state to accelerate its plans to stop the spread of Asian carp from states farther south in the Mississippi basin. But he also acknowledged that the findings raise more questions than they answer. No species of fish native to the lower stretch of the Mississippi has made it beyond the dam, so how could Asian carp, which have appeared only sporadically in recent years, have gotten past? In addition, the widely touted testing, which picks up DNA from carp mucus and excrement, has yet to lead officials to an actual fish in a new area.

State naturalists admit it's a head-scratcher. But because millions of dollars are riding on the outcome, Department of Natural Resources (DNR) officials said that they are acting on the assumption that the silver carp are here, at least in small numbers.

"The risk is too high to assume that there are not live fish north of the dam," Landwehr said.

If some have spread up the Mississippi, it's not too late to prevent them from becoming established, he added.

But conservation groups said the test results are bad news for Minnesota.

"All of the strategies ... relied on the presumption that they were not yet above the Coon Rapids Dam," said Don Arnosti, policy director for the Audubon Society of Minnesota. "I think it's a big shock to everybody."

The tests found DNA from silver carp, infamous for its tendency to leap out of the water at the sound of a motor.

It's one of four species of Asian carp that have been moving north along the nation's river systems since they escaped fish farm ponds in the South in the 1970s.

The fish are voracious eaters that consume 5 to 20 percent of their body weight each day. They feed on algae and other microscopic organisms that form the base of the food chain, often out-competing native fish. Scientists believe the carp could severely disrupt the aquatic ecosystems of Minnesota waters.

Costly barriers

The Legislature this year committed $16 million to re-build the Coon Rapids dam as a carp barrier. The state is also investigating whether two bubble barriers along the Mississippi -- one at the mouth of the St. Croix and one in front of the lock at the Ford Dam in Minneapolis -- would deter the fish. But just one would cost an estimated $9 million and would likely be only partially effective.

Gov. Mark Dayton has been pressuring members of Congress for legislation that would give the U.S. Army Corps of Engineers authority to close one of the locks and dams in Minneapolis -- widely considered the only sure-fire way of stopping the fish.

Now, some conservation groups are also calling for Dayton to press the federal government and neighboring states to join forces to stop the spread at points south of Minnesota.

That could include a noise-and-bubble barrier at Lock and Dam 19 in northern Iowa to deter the fish from coming past that busy commercial throughway. That may be the only way to protect the lower Mississippi and Lake Pepin, as well as the Whitewater, the Root and the Minnesota rivers.

"We have to find a way to kick up the national and regional response," Arnosti said.

No fish yet

The DNR, conservation groups and National Park Service officials have pooled resources to conduct the DNA testing.

Since September, they have found traces of carp DNA in the St. Croix below St. Croix Falls, in the Mississippi below Hastings and the Ford Dam and, now, above and below the Coon Rapids Dam.

Three out of 19 samples from above the Coon Rapids dam tested positive.

The officials are awaiting the results of samples taken above St. Croix Falls and other locations.

But even though the state hired commercial fishing operators to comb the waters, no actual carp have been found. That's also happened in other places where the fish are suspected.

That may be because the fish are elusive, fast swimmers and would be difficult to catch if there are only a few. Or it may mean that the DNA is getting into the river by some other means.

Kelly Baerwaldt, a carp expert with the U.S. Army Corps of Engineers, said that the federal agency is now trying to figure out if the carp DNA could appear without fish.

For instance, it could come from fertilizer made from carp caught in the Illinois and Missouri rivers.

It's also possible that it could come from the droppings of birds that have eaten the fish or because an angler used fingerling carp as bait.

But government officials and conservation groups said that they thought those possibilities were far-fetched.

"My favorite," said Irene Jones of the Friends of the Mississippi River, "is that someone who ate carp at a Chinese restaurant throws the carcass in the river. That's what I always do when I eat at a Chinese restaurant."

The most likely source of carp DNA, government and conservation officials said, is carp. Jones said the fish are known to spread rapidly during periods of flooding and high water, which is precisely what happened along the Mississippi this year.

That is also one of the conditions that can spark a sudden burst in their population, Baerwaldt said.

The carp were found in low numbers in the Illinois River until the early 1990s. But then there was a perfect combination of conditions, including the "sustained flood pulses that they use as a cue for spawning," she said.

That, she said, resulted in a "population explosion."

Josephine Marcotty • 612-673-7394