A University of Minnesota report says the numbers of Asian carp in Minnesota are relatively low, but the invasive species may pose a problem in the future.
"I think they've got the potential to be very damaging to our ecosystems because they're a great big fish that feeds at the lowest part of the food chain and we don't have anything like that here," explained Steve Hirsch, of the Minnesota Department of Natural Resources.
Scientists and natural resources managers from the new Minnesota Aquatic Invasive Species Research Center at the University of Minnesota (MAISRC), U.S. Geological Survey and the DNR took part in the study say water samples from the Mississippi and St. Croix rivers showed little evidence of bighead and silver carp DNA.
The study utilized an improved detection methodology that picks up on DNA fragments released to the environment (eDNA), taking 50 water samples from eight sites. A 2011 study focusing on eDNA previously showed positive results for silver carp in up to half of the samples collected from the two rivers, the University of Minnesota release said.
This time, however, the new study detected silver carp in Iowa, where the fish are known to be, but no eDNA was detected the sampling areas of the St. Croix and Mississippi. No bighead carp eDNA was detected in any location.
"It does not mean they are not there," warned Dr. Peter Sorensen, MAISRC director and leader of the research team. "I wish it did. It only means that the numbers are relatively low."
Sorensen explained that, despite the lack of eDNA results, fish may still be entering Minnesota waters from the south and there may be a breeding trend in the future, posing potential problems for Minnesota waters. In fact, commercial fishermen netted a silver carp near Winona as recently as February -- and that's exactly how the invasion started in Iowa.
"They've had the same sort of period where they had a few fish and when they increase, they tend to increase quite rapidly," Hirsch warned. "We're concerned that could happen here at some point."
It is important to note that the latest research is not stopping efforts to control the fish, including the assembly of an Asian carp barrier at Lock and Dam No. 1 across from the old Ford plant in St. Paul.
The invasive species was first detected entering the Mississippi River system in Arkansas in the 1980s.
Complete report: http://www.maisrc.umn.edu/