Oh, carp! Invasive fish keep moving north; they're on the St. Croix now

The Minnesota DNR confirms that both silver and bighead carp were found on the St. Croix last week.

Invasive carp are advancing further north and now both of the major invaders have reached the river that separates Minnesota from Wisconsin.

Minnesota's Department of Natural Resources confirmed Thursday that a silver carp was caught on the St. Croix near Prescott, Wisconsin, last week.

"This news is disappointing but not unexpected," the DNR's invasive fish coordinator said in the agency's statement.

Bighead carp had already been found on the St. Croix and both of the invasive fish live in the Mississippi River. Prescott is where the St. Croix empties into the Mississippi.

Why is this a problem?

Invasive carp – also known as Asian carp because they're native to that continent – are really big eaters. They can eat up to 20 percent of their weight per day and some of the fish grow to more than 100 pounds, the National Wildlife Foundation says. They eat the same stuff native fish eat (plankton) but the invaders don't leave much of it for the locals.

Also, in places where there are a lot of them, silver carp start to leap up out of the water. They especially do this when they are spooked by boat motors. When hundreds of really big fish start jumping in the air, boating stops being much fun, as videos like this and this show.

They might only be visiting the St. Croix

So they've now been found on the St. Croix, but that doesn't necessarily mean they're going to start breeding and raising invasive fish families there.

DNR invasive fish coordinator Nick Frohnauer says the carp caught last week were in an area where lots of different kinds of fish spend the winter. As the water warms up in the spring, those carp may well have moved back onto the Mississippi.

Then again, they might have moved further up the St. Croix. There's no way to be sure right now but the DNR says it will step up its monitoring of the area.

Learn more

Invasive carp have already moved most of the way up the Mississippi River. Minnesota naturally wants to keep them out of the northern lakes where fishing is big business. And keeping them out of the Great Lakes is a priority for all the adjacent states and provinces.

Minnesota has an Invasive Carp Action Plan that was revised a few years ago. Lots of states and provinces are working together in an Asian Carp Regional Coordinating Committee that also has an action plan for 2017.

The National Park Service has a good overview about invasive carp. And the U of M has an Aquatic Invasive Species Research Center that's working on how to stop them from advancing.

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