The common carp, shown above, has been a problem in Minnesota beginning not soon after it was imported here from Britain in the late 1880s.

Asian carp — should they ever arrive in breeding populations — will be a bigger problem, still.

So far, the DNR believes only "pioneering" individuals — most recently a bighead carp caught in the St. Croix River — are in waters as far north as the Twin Cities.

But no one knows for sure how many Asian carp are in area waters, because each of the species of Asian carp, including grass carp and the wildly jumping silver carp, are shy, elusive and difficult to net.

The DNR has said it will contract with a company this summer in an attempt to determine — if not how many Asian carp are in the upper Mississippi River near the Twin Cities — at least whether some individual Asian carp are here.

The testing is called eDNA, and it's the same method that's been used in the Chicago/Lake Michigan area to determine if Asian carp there have slipped through river and ship canal barriers intended to keep them out of Lake Michigan.

Dennis Anderson, Star Tribune

DNR invasive species prevention coordinator Jay Rendall said Tuesday that testing will be done sometime this summer. Earlier, the DNR had said the tests should occur during spring flooding. That timetable has now been adjusted — perhaps because the DNR has too few people to get these things done more quickly, especially given the intensified invasive species work the agency has undertaken this spring and summer.

Or perhaps because stuff just takes time. Either way, Rendall said the eDNA tests will be done this summer.

A second important issue is the possibility of installing a sonic bubbler system at Prescott, Wis., to keep Asian carp out of the St. Croix, assuming they swim upstream at least to that point.

Or if not keep them out completely, at least slow their invasion, perhaps allowing enough time for a miracle solution to be devised to undercut Asian carp populations.

It's fair to say that installing a sonic bubbler at Prescott wasn't very high on the DNR's to-do list this winter and spring — perhaps because of cost considerations, perhaps because of other invasive-species prevention priorities. But this appears now to have changed at least somewhat, as officials seem to be at least scoping out the possibility of installing a sonic bubbler at Prescott.

Already, the DNR has met with a vendor who makes the bubblers, and the vendor is waiting for flow rates and other river information the DNR must gather before a cost estimate can be established.

Regardless of the cost — and it might be $1 million or more — it's difficult to believe the feds, among others, including Minnesota and Wisconsin residents, won't demand that a river of the St. Croix's importance, regionally and nationally, won't be protected, if possible.

Regarding a potential Asian carp invasion this far north, consider also the Coon Rapids dam, which officials have said needs rebuilding. If improved and modified, the dam in most years could provide an upstream barrier to carp, the officials say, preventing them from entering the Rum River, Lake Mille Lacs and waters beyond.

The Legislature is nonetheless toying with the consummately bad idea of not funding the dam when and if they ever get a budget done. Go figure.

A final note: The National Park Service — which is called the National Park Service because it deals with parks, not carp — this spring weighed in on the possibility of rebuilding the Coon Rapids dam and said, essentially, that reconstructing it, at least if the intention is to prevent the upstream migration of carp, isn't an idea the service could support.

The NPS envisions instead the romantic notion of eliminating the lock and dam near downtown Minneapolis and returning the river to its once-natural state there, with the return of its barrier falls, over which Asian carp couldn't leap.

Fueling this fantasy, the NPS also envisions a new recreation area on the river near downtown Minneapolis, with white water for kayakers and other fun stuff.

This is the same National Park Service that wants to protect the St. Croix River by ensuring that — what? — any bridge over the river at Stillwater doesn't offend its sense of aesthetics, while, so far, remaining largely mum about what should be its top priority: preventing Asian carp from invading the St. Croix River at Prescott.

Which is all the more reason why DNR Commissioner Tom Landwehr will have to keep his eye on the Asian carp ball in coming weeks and months, to make sure his agency's bureaucracy, understaffed though it might be, doesn't miss important opportunities to protect the Mississippi and St. Croix rivers. To whit:

• He should insist to Gov. Dayton, his boss, that the Coon Rapids dam project be in any budget deal cut with the Republicans.

• He should ensure the eDNA testing gets done this summer on the Mississippi and the St. Croix, and upstream also in the Minnesota River.

• He should fast-track getting the necessary data to the makers of the sonic bubbler system that might be applicable for installation at Prescott.

Opportunities have been missed before to keep Asian carp out of Minnesota. There's no excuse for missing any more.