Attack of the invasive species: Data understate the degree of lake infestations

Fishing opener is this weekend; getting out there to start the season is on the minds of many. For many lakes around the state, this also corresponds to the start of aquatic invasive species (AIS) inspections at boat landings.

The Minnesota Department of Natural Resources (DNR) has worked hard to communicate that stopping the spread of AIS is important. But in the same breath, the DNR notes that AIS isn't affecting most lakes in Minnesota.

Both of these statements are true, but the latter one is very misleading. That's the problem with statistics. You can use them to say anything you want.

The 10,000 lakes we talk about are really closer to 11,842 that are 10 acres and larger. By any standard, that's a lot of lakes. Not all of them are accessible to boaters; there are only 2,238 watercraft trailer launches in the state as certified by the Department of Revenue when providing AIS Prevention Aid to the counties. Surely, boaters use many of the lakes that don't have public accesses, but those generally aren't the bigger and more popular lakes — all of which have public accesses.

The DNR says on its website that fewer than 7 percent of Minnesota's lakes are infested with one or more AIS. So maybe AIS isn't that big a problem. Still, 7 percent adds up to 828 lakes. Meanwhile, let's look a little closer.

How are the 10 biggest lakes in Minnesota faring in the battle against AIS? Setting the big 10 against the DNR's infested waters list from April 13, 2018, we find that nine of them have one or more of the most troublesome aquatic invasive species. That's 90 percent! And these vast AIS-infested lakes include famous names: Lake of the Woods, Rainy, Upper Red, Leech, Mille Lacs, Winnibigoshish, Vermillion, Kabetogama and Pepin.

Mille Lacs wins the booby prize for being infested with three of the nastiest AIS — zebra mussels, spiny waterfleas and Eurasian watermilfoil. Five of the big 10 lakes have spiny waterfleas, four have zebra mussels, three have Eurasian watermilfoil and two have starry stonewort, the newest nasty species, which was discovered in Minnesota in 2015.

The AIS problem gets somewhat less severe when you look at the 19 Minnesota lakes with more than 10,000 acres, but it's still a big problem. Of the 19 over 10,000 acres, only four have no known AIS. That means AIS infestations are found in 79 percent of our 19 biggest lakes.

I live in the metro area, so I wondered how big a problem AIS is in the seven-county area. Spoiler alert: It's much worse than a "7 percent" problem here, too.

Consider Carver County's lakes: 13 of its largest make up approximately 5,745 acres. Zebra mussels are in just three of those lakes, but those three are much larger than the other 10, representing 67 percent of the acreage. The DNR counts infested waters, not surface area, and by that reckoning zebra mussels are in 23 percent of the 13 largest Carver County lakes. Still not a "7 percent" problem.

Yes, I'm cherry picking to make a point. But looking at the seven-county metro area's 159 largest lakes, covering 52,513 acres, you'll find Eurasian watermilfoil infesting 51 percent of the lakes and 83 percent of the surface area. You'll find zebra mussels infesting 11 percent of the lakes and 51 percent of the surface area. Minnetonka, White Bear, Waconia and Prior lakes are all infested with AIS.

The takeaway is that AIS, properly understood, is not really a "7 percent" problem for the metro area or for the state. It is much more pervasive and needs more focus statewide.

So as the anglers head out this weekend for the opener, let's ask them to use their collective brainpower to outsmart the fish and also to come up with much better approaches to address the AIS crisis in the state. Surely, we don't need more fisheries collapses like we've seen with the walleyes at Mille Lacs, but that's what's on the table if we don't get this problem under control.

What we have been doing is not working.

Joe Shneider is an environmental activist. He is on the executive committee for MN COLA, the head of the Coalition of Minnehaha Creek Waters and the president of the Christmas Lake Homeowner's Association.