by T.W. Budig
ECM Capitol reporter
Department of Natural Resources (DNR) officials look to the use of sound, bubbles, and flashing strobe lights to block Asian carp at Lock and Dam No. 1 on the Mississippi River from swimming further upstream.
Whether the proposed fish barrier at the lock, located six miles downstream from St. Anthony Falls, would prove effective is consequential beyond the metro.
Only the Coon Rapids Dam currently stands between the voracious, hulking carp and Lake Mille Lacs.
If the carp get beyond the Coon Rapids Dam — an imperfect barrier — the Rum River provides access to the big lake to the north.
“The biggest concern right now would be Mille Lacs,” DNR Ecological and Waters Resources Director Steve Hirsch said.
Still, DNR officials indicate the multi-sensory barrier proposed for the lock must be considered experimental.
That’s because there’s nothing currently in use to compare the proposal to.
A report from Barr Engineering indicates an electrical barrier would be more effective, but officials deem the chance of the U.S. Army Corps of Engineers approving the use of an electrical barrier, hazardous to humans, damaging to the lock, as remote.
But a Barr official styled the multi-sensory barrier as having comparable effectiveness — no technological barrier is 100 percent effective, the report notes.
DNR officials view Lock and Dam No. 1 as having advantages not found elsewhere on the river.
For instance, the Ford Dam provides a solid fish barrier across a large portion of the river at the lock. And the lock itself has construction features not found in other locks that’s useful in blocking fish.
The Barr Engineering report reconfirms the best and likely only long-term solution to preventing the carp from infesting the Upper Mississippi River Watershed would be to permanently close the lock at Upper St. Anthony Falls in downtown Minneapolis.
But this would require an act of Congress, Hirsch said.
Officials look to starting construction on the barrier at Lock and Dam No. 1 in late autumn.
It could cost up to $19 million to complete, with an additional $250,000 annual cost to maintain and operate.
The DNR looks to the Minnesota Legislature this coming session for about $15 million in additional funding to pay for the barrier,
The U.S. Army Corps of Engineers would need to approve the installation.
DNR officials hope to have the barrier in operation by the spring of 2014.
Commercial fishermen sporadically catch silver and bighead Asian carp in the Mississippi — silver carp famous for leaping into the air when spooked — and a 47-pound bighead was caught near Red Wing last fall.
Still, DNR officials do not believe the carp are reproducing in Minnesota waters.
Asian carp often first appear in small numbers, Hirsch said.
But the population can quickly shoot up.
University of Minnesota and U.S. Geological Survey officials have been conducting eDNA testing in water samples collected in the vicinity of the Coon Rapids Dam.
Results are expected to be known by early March.
The test checks for the presence of Asian carp DNA in the water, indicating the carp have been in the area.
Two years ago tests from samples taken above and below Coon Rapids Dam indicated the presence of silver carp.
Nineteen of 48 water samples tested positive, with three of the 19 positive hits coming from water samples above the dam.
But scientists stress that multiple eDNA test hits do not necessary mean a large number of carp are present.
Indeed, a series of positive hits could come from a single fish, they note.
DNR officials repeated what others have said about protecting the Minnesota River from the Asian carp — it’s tough.
In terms of sites for potential barriers, they point all the way down stream to Mankato.
The sound, bubble, and flashing light barrier would not be that visible.
Humans would only notice the sound if underwater.
Asian carp are particularly sensitive to sound.