DNR explains environmental DNA

1) What is eDNA testing?
All fish, including invasive carp, shed DNA material into the environment through mucus and excrement. DNA floats on the water surface and accumulates in eddies and backwater areas. The presence of individual fish species can be detected by collecting water samples in those areas and filtering them in the lab for DNA. Specific invasive carp species can be identified using genetic markers that are unique to them.


2) What do the recent eDNA findings on the St. Croix and Mississippi rivers indicate?

A positive eDNA sample indicates that an organism of that species was in the area recently. DNA can originate from dead fish, or water containing invasive carp DNA may have been transported from other sources, such as bilge water.


3) Do the eDNA findings tell how many fish there are?

No. The technology can only indicate presence or absence of a fish. It cannot quantify the number that are present or provide real-time information on their location.


4) Has eDNA testing been used in other water bodies to detect carp?
Yes. Developed by scientists at the University of Notre Dame, the technology has been used on the Illinois River, Lake Calumet and the Calumet River near Chicago.


5) Why are invasive carp such a big concern?
Bighead and silver carp are voracious eaters, capable of eating 5 to 20 percent of their body weight each day. The diet of invasive carp overlaps with the diet of native fishes, meaning the carp compete directly with native fish for food. Invasive carp consume plankton—algae and other microscopic organisms—stripping the food web of the key source of food for small and big fish. Invasive carp can grow to large sizes – some as large as 110 pounds – though the average size is around 30-40 pounds. The silver carp is skittish and easily startled by the sound of a boat motor. The sound can cause the fish to leap as high as ten feet out of the water, earning them the nickname “the flying fish.” Some of these fish weigh more than 20 pounds. They land in boats, damage property, and injure people.


6) Where are invasive carp found now?
Established populations of invasive carp are found on the Mississippi River as far north as the Quad Cities in Iowa and Illinois, and significant numbers have been reported as far upstream as Dubuque, Iowa. Invasive carp also are abundant in the Illinois River and the lower Missouri River.


7) Have any live invasive carp showed up in Minnesota waters?
Invasive carp have been caught by commercial fishermen in the Mississippi and St. Croix rivers. On April 19, 2012 commercial fishermen working near Prescott, Wis., netted a 30-pound bighead carp from the St. Croix River where it flows into the Mississippi. That’s in addition to two other bighead carp caught in the lower part of the St. Croix.
The invasive carp found in the Mississippi were found in the lower stretches, from Lake City south. A 47-pound bighead carp was caught in a seine net by commercial fishermen on Nov. 16, 2012 in Lake Pepin near Frontenac. A silver carp and a bighead carp were caught in a seine net by commercial fishermen March 1, 2012 in Pool 6 of the Mississippi River near Winona. Other silver carp have been caught in Pool 8 and one in Pool 9 near the Iowa border. The catches occurred between 2008 and 2011.

Back to top