New test suggest Asian carp aren’t as prevalent as thought

Improved eDNA testing suggests that Asian carp, while occasionally netted in Minnesota waters, perhaps aren’t as prevalent as once believed.

A joint testing effort by the Minnesota Department of Natural Resources (DNR), the Minnesota Aquatic Invasive Species Research Center at the University of Minnesota (MAISRC), and U.S. Geological Survey failed to replicate 2011 testing results that showed positive hits for silver carp eDNA (genetic material from an organism found in the environment) upstream of the Coon Rapids Dam on the Mississippi River and elsewhere.

Rather than showing the Mississippi and St. Croix rivers dotted with positive hits, the 50 water samples taken last year from areas above and below St. Croix Falls, above and below the Coon Rapids Dam, or below Lock and Dam No. 1, or the Ford Dam, on the Mississippi, revealed no presence of silver carp DNA at all.

That does not mean  officials recommend the state abandon efforts at combating the spread of Asian carp.

“The rivers are wide open,” said Professor Peter Sorensen, MAISRC director, who lead the most recent research work.

“The good news here is there’s still time to do something,” he said.

Although saying he could not pinpoint why the test results differed — the 2011 water samples no longer exist, he noted — Sorensen styled the latest testing, which used U.S. Army Corps of Engineer protocols, as a magnitude-factor better than the earlier test.

It’s possible the 2011 tests did actually detect the presence of silver carp DNA but that the fish simply aren’t here now, Sorensen said.

“We don’t have a time machine,” he said of bringing back the original water samples.

Testing technology is improving, Sorensen indicated, and the use of sterile “Judas” fish –  or carp implanted with transmitters to betray the presence of other carp – holds promise for more exacting data.

“(But) I can’t precisely tell you (when),” he said.

The DNR maintains that while Asian carp sometimes  ply Minnesota waters — one was pulled to the surface near Winona in February — the number is low, too few for a breeding population.

Not that they can’t live here.

“They’re a pretty tough fish,” Sorensen said.

A number of steps are currently underway to combat the invasive carp.

Construction on the Coon Rapids Dam to make it a stouter fish barrier is expected to be completed next year.

Some $16 million was slated towards the project, the dam seen as critical in protecting the Upper Mississippi, the Rum River, and Lake Mille Lacs from the carp.

According to a DNR official, a firm has been hired to design an electronic fish barrier for use at Lock and Dam No. 1.

Sorensen expressed comfort with using U.S. Army Corps of Engineer testing protocols, though the corps is responsible for lock operations.

One proposal to halt the spread of Asian carp is closing some locks.

Sorensen described the recent testing as “diligent” and transparent.

But refinements are needed.

Indeed, no bighead carp eDNA was detected in Iowa waters, where the carp is known to exist, shows the need for improvements.

Democratic Gov. Mark Dayton has held a series of Asian carp summits at the State Capitol to coordinate state response to the invasive species.

“Aquatic invasive species is still an urgent issue facing the state and the region, and this news does not change the governor’s position,” said Dayton Press Secretary Katharine Tinucci.