Minnesota: Search continues for Asian carp in St. Croix River
After a five-day search, Minnesota Department of Natural
Resources (DNR) fisheries staff did not capture any Asian carp in
the St. Croix River, but efforts to locate them continue this
Last week, DNR fisheries biologists used trawling techniques and
electro-shock fishing methods to sample fish populations in two
stretches of river. On Aug. 15 and Aug. 16, crews sampled sections
of the river below the St. Croix Falls dam. This is where 22 out of
50 environmental DNA (eDNA) samples taken in June suggested the
presence of silver carp, an invasive species.
From Aug. 17 to Aug. 19, fisheries crews searched the lower reaches
of the river near Prescott, Wis., where a bighead carp, another
Asian species, was caught by a commercial fisherman in April.
No Asian carp were caught during the searches.
“This is good news because it suggests that if Asian carp are
present, the population could be very low, perhaps only a few
individuals,” said DNR Commissioner Tom Landwehr.
Starting Tuesday, a commercial fisherman hired by the DNR will
begin using large nets to try to capture Asian carp in the St.
Croix. The gear is larger than what DNR fisheries crews typically
use. The fisherman may also use large seine nets. Both techniques
have been effective in catching Asian carp. The contract for the
commercial operation was expedited in response to the positive eDNA
results announced earlier this month.
This week, the DNR will also present information to the
Lessard-Sams Outdoor Heritage Council (LSOHC) about a proposed
sonic bubbling system that would discourage Asian carp from
entering the St. Croix River. The LSOHC recommends spending to the
Minnesota Legislature for a portion of the Land, Clean Water and
Legacy Amendment approved by voters in 2008.
The system would use a combination of bubbles and sound to direct
the invasive species away from the river’s mouth. Asian carp are
sensitive to noise, and the device would be calibrated to target
Scientists believe the barrier would not be a 100-percent deterrent
to Asian carp, but it could keep populations low while other
control methods are developed.
Bighead and silver carp are voracious eaters, capable of eating 5
to 20 percent of their body weight each day. Asian carp feed on
algae and other microscopic organisms, often outcompeting native
fishfor food. Scientists believe the fish could severely disrupt
the aquatic ecosystems of Minnesota waters.