Changes to Mississippi River dam may block Asian carp spread
Post Bulletin, 9/5/2017
The U.S. Army Corps of Engineers, St. Paul District, recently made operational changes to a Mississippi River dam to control the spread of an invasive species.
The Corps changed the way it operates Lock and Dam 8, on the Mississippi River in Genoa, Wis., to block the upstream migration of Asian carp. The alteration was made in response to recommendations from University of Minnesota researchers.
Dr. Peter Sorensen, who led the university research team's work, spoke with the Post Bulletin last week about the changes and how they'll affect Minnesota's water bodies.
The U.S. Army Corps of Engineers recently changed its operation of Lock and Dam 8 on the Mississippi River in Genoa, WI to impede the movement of Asian carp. I understand the corps changed the operation in response to your research. Can you briefly summarize your findings?
This is a result of a long, longstanding project that started almost four or five years ago. We realized some time ago that it was rather mysterious that the Asian carp have not really become more abundant in Minnesota waters. And we wondered if it was the locks and dams, which are particularly large at this end of the Mississippi and smaller down below.
We got the money from the lottery funds in Minnesota, and one of the first things we did was we actually figured out what the swimming capabilities of these carp are. We calculated how far and how fast they can swim; every species has certain capabilities, and we figured out that they actually are nothing really that extraordinary as far as a river fish goes. So, it was possible that the locks and dams were holding them up even though they jump.
Once we had that information, we then approached the Army corps (to see) if they would be interested in working with us to first see what the actual velocities were through certain lock and dam structures. There were weaknesses where a fish could pass through.
Why make the operational changes at Lock and Dam 8? Is that the main channel of invasion for Asian carp?
That's as far south as we could go. Certain locks and dams are more amenable than others because some, for instance, have spillways around the edges where carp can get around, and things like that. Each one's different than the other. Some are just better for this, and that was a pretty good one, although not perfect. It was located almost in the Iowa border down there.
How will the operational changes to Lock and Dam 8 prevent the spread of Asian carp here in Minnesota?
It's based on theoretical models. It's the best we can do right now. They seem very reasonable and they've been validated to a fairly good extent in the river. Basically, the mathematical model suggests that just by adjusting the gates, that whatever the passage rate is now, which we believe to be very low, it will probably be cut at least in half. They can only go so far and so fast, and the data suggest most of the time, except for very brief moments, they are not going to get through.
What do Asian carp do to water bodies?
They eat all the young in there, and that's basically what they do. They eat all the planktonic food in the water; fish eggs, you name it. They grow fast, so that disrupts food webs and has effects in terms of native fish that eat planktonic food. From most people's perspective, that's bad. But what's really terrible of course (is) they jump out of the water. It'll be devastating. People would hesitate to go out in the river, which is what's happened down south of us in Iowa, Illinois, Kentucky, Pennsylvania, the Dakotas.
Once they get in and they're jumping, they weigh 20, 30 pounds and they jump eight feet out of the water. It'll break your arm. This nice quiet evening paddle on the river or fishing excursion will never be the same again. That's what's at stake.
How big of a problem are they in Minnesota?
Right now, they're not a problem. There are very few. We catch a few every year, but we're catching large adults that are reproductively mature. So they could reproduce, and if they were to reproduce, then we'd have a very serious problem. What most biologists are most concerned about is actually the Minnesota River, because it's almost perfect habitat for them. They'd have a place to reproduce and grow like crazy, from there they could infest everywhere. If we survive as a species as I hope we do, your great-grandkids will be dealing with them and cursing you for having let them in when it wasn't really a preordained conclusion. It's important to act on invasive species while it's reasonable to do so.
Do you see the change at this dam as an effective long-term deterrent for Minnesota's Asian carp population?
Yes, I do. Particularly if the sound systems can be upgraded and it can be combined with other structures upstream, yeah I think it can buy us decades at very low cost.