(chill guitar music) - [Bret] The land and waters along Minnesota's northern border have not been spoiled by many of the non-native species wreaking havoc in other parts of the state.

(chill guitar music) Still, invaders are creeping in.

Earthworms are chewing up forest floors and rusty crayfish are threatening lake shores and wild rice production.

(chill guitar music) Researchers are testing ways to kick them out.

(chill guitar music) (upbeat bass music) Rusty crayfish looked like miniature lobsters, similar to their native cousins like Calico and Northern Clearwater crayfish But Rusties are bigger, more aggressive, and sport a reddish-brown patch on their shell.

About 40 years ago, they started moving in to the upper Midwest.

(upbeat instrumental music) - The rusty crayfish is native to the Ohio River Basin.

And as far as anyone can tell, they were moved here by anglers using them as bait.

There's a couple of other theories.

Rusty crayfish, because they're easily trappable, they were one of the crayfish that they would send to high schools to, you know, learn dissections and things like that.

And so it's possible that, you know, high schools had extra and they released them.

There's also a contention that, maybe some people that wanted to catch crayfish and sell them as bait, were bringing them up and releasing them into small lakes to start populations where, because they're very trappable, they could catch them and sell 'em as bait.

(gentle piano music) They are across the whole Great Lakes region, the whole upper Midwest in 20 states.

They've even been found now in some of the western states.

The Rusties, they're aggressive, they're really voracious, they're really productive.

They start eating more of the fish eggs, they start eating more of the snails.

And so they could actually change the fish population of a lake.

They can change the vegetation on the shoreline of a lake.

So really, change that whole ecosystem.

And that's what people are upset about.

You know, we're losing our native crayfish and these aggressive things are just changing the lake.

(playful instrumental music) - [Bret] University of Minnesota researchers based at the Natural Resources Research Institute in Duluth are evaluating ways to trap and remove the invasive crustaceans from lakes.

Their work is funded by the Minnesota Environment and Natural Resources Trust Fund - We designed this project because we heard that everybody was worried about wild rice because of rusty crayfish.

Though, rusty crayfish can go in and just literally just chop off the wild rice.

We can't control rusty crayfish statewide on our own.

But we thought, well, if there are lake associations or tribal groups that want to try to protect wild rice and other sensitive vegetation, let's see if we can figure out the best trapping methods for them to use to reduce the po and protect those sensitive area (water splashes) And so, that's what we're doing.

What bait works best?

What kinds of traps work best?

- [Bret] University researchers with three organizations to test trapping methods at Dumbbell, Caribou, and Tofte Lakes.

- [Valerie] For this lake, we're partnering with 1854 Treaty Authority and they're out helping us.

So they do half the traps, we do half the traps.

- The 1854 Treaty Authority is an Inter-tribal natural resource management agency So we are governed by Bois Forte and Grand Portage bands of Lake Superior Chippewa.

Our main concern with rusty crayfish is that they're a non-native species.

and they have a detrimental impact on the plant communities here specifically, one of our focuses is manoomin, or wild rice.

It's particularly susceptible to grazing by rusty crayfish.

So we did some exclosure/enclosure work where we fenced off areas of wild rice and then either trapped and removed all the rusty crayfish from within that enclosure or stocked rusty crayfish in their And then, you know, as the summer went on, we just documented the growth of wild rice within that fenced in area.

We found that, you know, with a lack of rusty crayfish within an area, the wild rice tended to grow better.

If we stocked a bunch of crayfish in there, then they ate all the wild rice.

(upbeat percussive music) - [Bret] In early August, we joined researchers on Tofte Lake near Ely.

(upbeat percussive music) - When we were here earlier at this lake, we marked the crayfish.

So we put pinholes in their tails and those pinholes tell when and where we caught this crayfish so that if we recapture them, we'll be able to see, "Okay, how far did it go?"

This is to be able to tell people how far away from your wild rice bed, for example, do you have to set traps in order to really reduce the population?

(upbeat percussive music) So the two boats are gonna go in and start working on these traps They're gonna be pulling up the dumping out the crayfish, (crayfish thumps) ID-ing them 'cause we lkhave a mix of native and invasive crayfish in this lake.

And then, the native crayfish get put back, (water sloshes) the invasive crayfish, we measure them, check to see if they've been marked, and then the invasive crayfish get killed.

(upbeat percussive music) 1854 crew just pulled in a trap.

You can see these are standard minnow traps.

All we've done is make the opening a little wider so the crayfish can get in easily 'cause if they can't get in easily they're not gonna go in.

(upbeat instrumental music) - [Bret] Researchers determined hot dogs are the best bait for attracting crayfish.

- Rusty crayfish are omnivores.

They will eat anything that they think is munchy.

And of course, protein is a good you know, a good food source.

So what we believe is that they have chemo sensors.

They can sense carrion, the chemicals that come off of decomposing meat, and they'll follow it up current to wherever that is.

And we all know they eat, you know, dead fish and decaying stuff in lakes.

You see crayfish on them.

So that's what they're doing with a hot dog.

(upbeat instrumental music) Tried cat food and frozen smelt, and of course those two baits were a little harder to work wit Looking for the things that are easy for landowners and lake associations and tribes to use.

So hot dogs work just fine.

Hot dogs are easy.

We'll go with hot dogs.

(upbeat instrumental music) One of the things about rusties is just, they are so much more aggressive than most of the native species, and they're really territorial about food resources.

That's partly how we think they pushed the native populations out.

I have been chased around the boat by a mad crayfish this big.

Rusties are just crazy!

Native crayfish, they'll go into a defensive posture.

Rusty crayfish will actually chase you.

They get their pinchers up, and it's ridiculous.

I am, like, 200 times bigger than you.

(upbeat hip hop music) Just have the minnow traps and the refuge traps.

The minnow traps with the hotdog in 'em with a bait actually attract many more males than females.

And what you need for population control is you gotta get rid of the females.

So one of our ideas was that if we gave the females with eggs a place to hide, something called a refuge, we would get more females.

Unfortunately, we haven't been getting much.

We said we'd try it, so we tried it.

That's what research is, you know You don't know for sure 'til you try.

Zero's our data.

(laughs) (upbeat instrumental music) - [Bret] Many native crayfish species are only in a few lakes or river systems - [Valerie] And so you introduce an invasive into that system and you could extricate an entire species, or several species.

So they're very worried about things like rusty crayfish getting in.

And of course, now we've got the new crayfish coming in from the south, the Signal Crayfish, and it's big!

It gets lobster-sized!

We don't know how far north it will spread.

So far, it's only in the south.

But everybody's worried.

'cause this thing's huge, and much larger than any of anything we have up here.

Red Swamp crayfish, also invading from the south.

These crayfish are really marching north to get us.

(music concludes) (bright guitar music) You know, you would look at a lake like this and you would think, "It's perfect, There's nothing here."

And then, there's those rusty crayfish, right?

And then, if we go in the forest we might see that there's the earthworms eating everything.

That's why we want anglers to be very careful about their bait.

I mean, most people don't know that all the earthworms up here are invasive, and they're just denuding the forest floor and the trees can't regenerate 'cause they kill them all.

All bait should go in the trash.

Put it in your freezer It's the most painless death you can give them.

It seems cruel and harsh, but it's best for the ecology of that they not go back.

- [Bret] Crayfish are also delicious to eat.

- Minnesota Sea Grant sponsored crayfish boils with rusty crayfish.

What better way to get rid of your invasive species than to eat them?

So highly encouraged.

If anybody wants to do it, just boil 'em up good!

(upbeat instrumental music) For many years we've loaned our traps to folks in the White Iron Chain of Lakes and they've been trapping like crazy for, I think, a decade.

And it seems to be working.

(upbeat instrumental music) We've seen other studies that show that some fish can actually help control rusty crayfish populations, particularly fish that eat the eggs or eat the young.

So one of our ideas is that lake associations could do a whole lot of trapping, really get rusty crayfish populations down, and then maybe the fish could control it from there.

(water splashes) - Ideally, what we would wanna see is some kind of management tool.

If we could package this and give it to lake associations or, you know, other natural resource managers if they want to help restore vegetation beds on lakes, that would be great to see.

If we can see more manoomin on the landscape, even better.

(upbeat instrumental music concludes) - [Announcer] Stories about aquatic invasive species research are brought to you by the Aquatic Invasive Species Task Forces of Meeker, Yellow Medicine, Lac Qui Parle, Swift, and Big Stone counties, and by the Environment and Natural Resources Trust Fund.

(calm instrumental music) We can stop aquatic hitchhikers from infesting more lakes and streams by cleaning up everything we pull out of the water.

It's a simple drill.

Clean in, clean out.

Before leaving a water access, clean your boat and water equipment, remove and dispose of all plants and aquatic species in the trash, drain water from your boat, ballast tanks, motor, live well, and bait container, remove drain plugs, and keep drain plugs out while transporting equipment.

Dispose of unwanted bait in the trash.

To keep live bait, drain the water and refill the bait container with bottled or tap water.

And if you have been in infested waters, also spray your boat with high pressure water, rinse with very hot water, dry for at least five days.

Stop the spread of AIS.