The Minnesota Department of Natural Resources announced today that recent tests indicate Silver carp, one of the invasive Asian carp species, are present in the St. Croix River, potentially as far up the river as the dam at St. Croix Falls:
Water samples from the St. Croix River have tested positive for genetic material from silver carp, suggesting the invasive, leaping Asian species may be present in the river as far north as the dam at St. Croix Falls, according to the Minnesota Department of Natural Resources (DNR).
Known as environmental DNA (eDNA) testing, the results do not provide any information on number of fish present, their size or whether they are breeding.
To date, no silver carp have been caught in the St. Croix River, either by anglers or commercial fishing operators. Only two bighead carp, a different Asian species, have been caught in the river – one in 1996 and another on April 18 of this year.
The discovery has prompted the DNR to take several actions.
“Our immediate goal is to mobilize as much effort as possible to confirm the presence of live silver carp in the St. Croix,” DNR Commissioner Tom Landwehr. “The results raise the profile and the level of urgency around the Asian carp issue not just for the DNR, but for all agencies, conservation groups, municipalities and river users who have a stake in the health of the St. Croix and the Mississippi.”
The DNR will soon contract with commercial fishing operators to begin using nets on the St. Croix to try to capture live silver carp in the same areas where eDNA tests were positive. DNR staff will also use nets and boats outfitted with electric shocking capabilities to search for fish. DNR operations could start next week; commercial netting operations are expected to start by the end of August.
DNR officials said they will proceed with development of a bubble or sonic barrier at the mouth of the St. Croix River at Prescott, Wis., pending results of the additional carp sampling. Scientists believe such a barrier would not be a 100-percent deterrent to Asian carp, but if the populations are low, the barrier could help keep additional carp out of the river while other population control methods are developed.
The DNR is considering a variety of funding sources, including requesting assistance from the Minnesota Legislature, for the barrier. A recent estimate put the barrier’s construction cost (for materials alone) at $7 million.
We reported in April about the finding of a similar carp, of the Bighead variety, near Prescott, which raised red flags at the time.