A broad multi-agency study has found no evidence that Asian Carp are established in the St. Croix River.
The announcement today contradicts a report last year which stated carp DNA had been found in water all the way up to the St. Croix Falls dam. The method used in that study have since been shown to produce incorrect results, due to the possibility of DNA being transported by birds, boats, and other means.
Today’s report compared the results of the testing in Iowa, where the carp are know to be present, with testing in the St. Croix and Mississippi Rivers. From a news release:
According to the researchers, while the new study consistently detected silver carp eDNA in Iowa where the fish are abundant, it detected no silver carp eDNA in the sampling areas just above and below St. Croix Falls in the St. Croix River or in the sampling areas above and below the Coon Rapids Dam or below Lock and Dam No. 1 in the Mississippi River. In contrast, no bighead carp eDNA was detected at any location, including in Iowa where this species is known to be present.
This comparison indicates that the testing is reliable in detecting the fish, and that the fish are not present in the river around the barrier dam at St. Croix Falls. It also suggests that the testing is ineffective at detecting the presence of one species of the invasive fish, Bighead carp.
Scientists involved in the new research said that, despite the absence of carp evidence, action is still necessary to prevent their spread into the St. Croix and upper Mississippi Rivers.
In a summary of the report, Dr. Peter Sorensen of the University of Minnesota’s Aquatic Invasive Species Research Center, wrote, “The continuing capture of Asian carps in Minnesota and their large size and mobility speaks to the need to take all possible measures to develop better measurement tools (such as eDNA and enhanced netting ) and to delay their movement, while developing control techniques.”