Think Out Loud

A new plan to eradicate invasive trout in an Eastern Oregon forest

By Rolando Hernandez (OPB)
March 27, 2023 4:32 p.m. Updated: March 27, 2023 7:53 p.m.

Broadcast: Monday, March 27

Bull trout.

In 1998, the bull trout was listed as threatened under the Endangered Species Act. Efforts to help recover population numbers in waterways of Malheur National Forest have been met with some challenges as the invasive brook trout has been out-competing with native wildlife. A new plan hopes to eradicate the invasive fish from High Lake and Lake Creek.

U.S. Fish and Wildlife Service


The invasive brook trout is out-competing with the native and threatened bull trout in the waterways of the Malheur National Forest. Now, new efforts are underway to eradicate the invasive fish from High Lake and Lake Creek starting this summer. An advisory committee composed of U.S. Fish and Wildlife Service, U.S. Bureau of Reclamation, U.S. Forest Service, Oregon Fish and Wildlife and the Burns Paiute Tribe will oversee and undertake the project. Brandon Haslick is the Fisheries Program Manager for the tribe. He joins us to share the details of the plan and the damage the brook trout has caused.

The following transcript was created by a computer and edited by a volunteer:

Dave Miller: From the Gert Boyle Studio at OPB, this is Think Out Loud. I’m Dave Miller. Invasive brook trout are out-competing native and endangered bull trout in waterways in the Malheur National Forest. So far efforts to control brook trout as a way to help the native species haven’t worked. So this summer, a consortium of wildlife managers from Tribal, state and federal Agencies are gonna try something else: a plant-derived toxin called rotenone. Brandon Haslick is the Fisheries Program Manager for the Burns Paiute Tribe and he joins us now. It’s good to have you on Think Out Loud.

Brandon Haslick: Thanks for having me on, Dave.

Miller: How did brook trout end up in waterways in the Malheur National Forest?

Haslick: Well, they were brought here, actually, by fisheries professionals, unfortunately. It was kind of a different time, when there were different goals. We wanted to create really favorable angling conditions in certain areas. And so a lot of the fishless lakes and bodies of water out west were stocked with fish that just weren’t native to the system and it was kind of a similar story back out east. We brought fish out here and took them over there, and did the same thing. So we wouldn’t do those things today. But we learned from our mistakes and now have a better way to move fisheries management forward.

Miller: What have brook trout done to native bull trout populations?

Haslick: Specifically with bull trout, one of the main problems there is that because they’re a closely related enough species, they can actually spawn with brook trout. And so what you end up having is a hybrid that comes out of that equation, which is neither brook trout or bull trout. But regardless, it’s not very beneficial for the bull trout populations because that individual is then able to continue that process…

Miller: Because those are fertile hybrids, they can propagate as well.

Haslick: That’s correct. Exactly. So what you end up having is a situation where you’re just watering down these bull trout genetics in such a way that the genetic purity of the bull trout species is then at risk.

Miller: The Burns Paiute Tribe has been trying to reduce the population of brook trout to help bull trout for about a decade now. Can you give us a sense for what kinds of methods you’ve been using?


Haslick: Yeah, sure. The Tribe has tried a number of different methods in order to reduce or make an impact in this brook trout population in the Malheur. We started with an electric fishing program in one of the main channels, where they were originally introduced. And that’s Lake Creek in the Malheur Basin. So we focused in there, because there’s an upstream lake in that system that kind of forms the headwaters and that’s called High Lake. And that area, specifically, is where the brook trout were originally introduced. And so we knew we had high concentrations of brook trout in that system. And basically, there’s also a barrier to fish movement. So native fish can’t go beyond this natural feature called Lake Creek Falls. Above that point, it’s all brook trout, all the time. There’s no competition up there and it kind of allows these fish to continuously move down into the lower Malheur system. And so what we did is we started with electrofishing and gillnetting in High Lake.

Electrofishing is basically this method where you run an electrical current through the water and it stuns the fish. And you’re then able to easily capture them and you can put them in a bucket, take measurements and do whatever while the fish is basically motionless. And then because the fish is just stunned, if it’s a native fish, you can return it to the water. But if it’s an introduced or non-native brook trout then you can just remove it from the system. So we did that and we coupled that with gillnetting at High Lake because we have a lot of fish up there as well and gillnetting is just stringing these really long nets across the lake and the fish swim in and can’t get out. So then we’ll go in and just grab them that way.

Miller: But it seems that wasn’t enough to really move the needle here in terms of helping the native fish. And that’s where this plant toxin rotenone comes in? What’s the plan for what you’re gonna be doing this summer and next summer?

Haslick: Unfortunately, like you were saying, we just didn’t find we were having the desired effect. We didn’t see native fish numbers increase. And our population estimates that we did along with the mechanical removal, showed us that we were still fighting a losing battle. We still had brook trout outnumbering bull trout by about twenty to one. We knew we had to look at other options and that’s where we started thinking about, maybe we could try this piscicide called rotenone and it’s been successfully used in other basins and other systems. Basically what it does is it messes with the metabolic uptake of oxygen at the gill level. The fish essentially, its cells shut down and once you have enough cells shut down, you have major organs and the fish just basically, kind of just goes to sleep . . .

Miller: Forever.

Haslick: Exactly.

Miller: Dies.

Haslick: Yeah.

Miller: Ok. We just have about two minutes left. But my understanding is that rotenone kills all fish. So, how are you going to prevent native bull trout from also being killed by this toxin?

Haslick: Yeah, that’s a very good question. Luckily for us, in the High Lake and everything above the falls, we only have brook trout. And what we’re gonna do is set up a detox station at the falls, and this detox is a potassium permanganate that we then allow to mix with the rotenone that’s coming down from the top from the falls there and that completely neutralizes it. It takes a little while for it to mix in the system. And because it takes a bit of time, what we’re gonna do with the native fish populations that are really close to that location is that we’ll go in and salvage. So we’ll kind of set some block-nets up and then do the electric fishing and remove the fish out of that area of danger. And we can take them downstream into a place where they’d be then safe from the effects of the mixing, potassium permanganates and rotenone.

Miller: Brandon Haslick, thanks very much for joining us.

Haslick: Thanks for having me.

Miller: Brandon Haslick is a Fisheries Program Manager for the Burns Paiute Tribe.

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