By Don Davis
New tests showing Asian carp likely are not colonizing Minnesota waters should not slow efforts to stop the invasive fish, experts say.
“The results certainly don’t say we should be doing anything different than we are right now,” said Steve Hirsch of the Department of Natural Resources.
Hirsch and other Asian carp experts reacted to Thursday’s release of a study that found no indication that many of the carp are in Minnesota’s Mississippi and St. Croix rivers.
Director Peter Sorensen of the Minnesota Aquatic Invasive Species Research Center at the University of Minnesota said the 2012 river survey that forms the basis of Thursday’s report was far more rigorous than one in 2011 that showed the carp could have been in Minnesota.
“The good news here is there is still time to do something,” Sorensen said.
Even with good news in the new report, Sorensen, Hirsch and others said that without taking defensive measures the carp probably will invade Minnesota from the south and eventually breed and establish large colonies in the state.
“They are pretty tough fish,” Sorensen said, and would have no trouble living in Minnesota rivers.
Hirsch said state and federal governments should continue efforts to build a carp barrier on the Mississippi River in Minneapolis or St. Paul. More attention also will be paid to keeping carp out of the Minnesota River, the DNR’s Brad Parsons said.
While the new environmental DNA study data does not show silver and bighead carp are prevalent in Minnesota, a few of the fish have been caught in the Mississippi and St. Croix rivers in the past decade.
Thursday’s report, called the most rigorous Minnesota study of the issue, showed that silver carp likely are in Iowa, but it found no evidence the fish are in Minnesota. No bighead carp DNA was found in Iowa or Minnesota, but Sorensen said the so-called eDNA test may not be able to detect bighead.
“This particular technique needs to be refined for detecting this species in open waters,” Sorensen said.
Asian carp experts say that before the fish arrive in large numbers, they are difficult to detect.
Silver and bighead are among species of Asian carp, fish imported from Asia that escaped Southern U.S. ponds in the 1970s and started moving north. They weigh up to 100 pounds and eat so much food that native species may starve.
Minnesota must continue efforts to fight the fish, Hirsch said.
“The threat of Asian carp is, nevertheless, an urgent issue for the state, requiring immediate action,” Hirsch said.
The Legislature and Gov. Mark Dayton are considering funding fish barriers and dealing with the U.S. Army Corps of Engineers, which controls locks and dams where barriers could be placed.
While the Minnesota report was being released, another study came out saying it is likely that at least some Asian carp are in the Great Lakes.
DNA tests similar to those used in the Minnesota study showed the evidence, The Associated Press reported.
“The most plausible explanation is still that there are some carp out there,” said Christopher Jerde of the University of Notre Dame. “We can be cautiously optimistic … that we’re not at the point where they’ll start reproducing, spreading further and doing serious damage.”