Yellowstone National Park and state of Montana fisheries crews devoted an entire week to poisoning unwanted, nonnative brook trout out of Soda Butte Creek back in 2015.

When rotenone, a chemical used to poison fish, coursed through the 38 stream-miles of the Lamar River tributary that summer, some 450 brook trout went belly up. 

The next summer, in 2016, two surviving brook trout were detected. The northwestern Wyoming and southern Montana watershed got another dose of poison to ensure that the creek would remain a stronghold for the native species: Yellowstone cutthroat trout. 

For five straight years afterward, no brook trout, a cutthroat competitor, were detected via routine monitoring and “eDNA” technology, which detects the whole suite of species in a waterway with great precision.

Yellowstone had won the fight against brook trout, at least in the embattled Soda Butte Creek watershed, so it seemed. 

Brook trout, pictured, are a fall-spawning fish that can outcompete native cutthroat trout, especially in smaller headwaters streams. (National Park Service)

Then last fall Yellowstone Fisheries Supervisor Todd Koel got discouraging news. 

In a one-mile stretch of Soda Butte Creek, electrofishing crews discovered 15 or 16 brook trout. And they were a few different sizes, suggesting different age classes. The pod of brookies materialized from out of nowhere — or they got a helping hand from a human illegally tinkering with the fishery. 

“It’s a good chance of that, unfortunately,” Koel said. “It’s a good chance. That’s how lake trout got to Yellowstone Lake, right?” 

Talking with WyoFile, Koel and Montana Fish, Wildlife and Parks Regional Fisheries Manager Shannon Blackburn were clear: There’s no hard evidence that newly discovered brook trout in the split Montana-Wyoming stream were the work of a bucket biologist. 

At least not yet. 

“I really wish we knew where they came from,” Blackburn said. “It’s so hard to say, but hopefully between potential genetic analysis and some other microchemistry, we can get a better idea of the source.” 

Potentially, they can pinpoint the source with precision. Fisheries scientists can analyze a bone called otoliths in the brook trouts’ ears to tell them exactly where the unwanted salmonids came from. And there are some likely sources. 

“There’s a gravel road that goes right from the campground right at Cooke City,” Koel said. “You can go right up the road to access lakes up high.” 

Those lakes are in another watershed, he said, and they contain brook trout. 

With little exception, Koel said, the 2015 operation to remove brook trout from Soda Butte was broadly supported

“There’s just one person that I know of who, for some reason, liked brook trout to be in Upper Soda Butte Creek,” he said, “and he’s not from the area.”

Notably, the reinvaded or reintroduced brook trout in Soda Butte Creek haven’t yet gained much ground. Using eDNA, Koel and Blackburn’s crews determined they’re confined to a small isolated stretch of the stream in Yellowstone. Once again, they’re bringing out the rotenone. 

“It’s kind of a smaller spot treatment to remove these fish,” Koel said. “We’re not treating all of upper Soda Butte, we’re only treating the mainstem from the park boundary down to Ice Box Falls.” 

Nearly 10 miles of Soda Butte Creek will be closed the week of Aug. 14-18, spanning from the Yellowstone National Park boundary downstream to Ice Box Canyon. (National Park Service)

For the first time in seven years, fisheries crews will be dispensing the piscicide in those 9.6 stream miles next week. The operation is expected to span the whole week, Aug. 14 to 18, during which time Soda Butte Creek will be closed to angling and swimming. 

Mostly, the cutthroat will be spared. While Koel and Blackburn were talking to reporters on Thursday, their crews were wading Soda Butte Creek’s waters to electroshock the stream and salvage the natives. 

Other crews are out there seeing if they can find any more brook trout. 

“So far, nothing,” Blackburn said. “Just cutthroat.” 

Mike Koshmrl reports on Wyoming's wildlife and natural resources. Prior to joining WyoFile, he spent nearly a decade covering the Greater Yellowstone Ecosystem’s wild places and creatures for the Jackson...

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  1. Electroshocking to remove brook trout was working for around 20 years on Soda Butte Creek until they chose to use rotenone in 2015. They quickly shifted from suppression policy to a zero-tolerance policy. They stated that brook trout were ready to invade the Lamar River! Really? Here’s the data.

    The section from Road Bridge 2 to Ice Box Canyon (Site 9), the section closest to the Lamar River, a brook trout was never captured from years 2004 through 2014; some years they didn’t even bother to electroshock this section. The section between Road Bridge 1 and Road Bridge 2 (Site 8), the section currently being poisoned in 2023, had 19 brook trout removed in 2013 and just 3 brook trout in 2014. Again, invading the Lamar – didn’t look like it.

    All 9 sections of Soda Butte Creek plus tributaries showed a 91% reduction in the brook trout population via electroshocking from years 2004 through 2014. In year 2014 only 109 brook trout were captured and removed in the entire Soda Butte Creek drainage.

    Ditch the rotenone and go back to electroshocking. Are they going to poison Soda Butte Creek and stress the cutthroats, macroinvertebrates and ecosystem anytime they find a brookie? That looks like their plan.

  2. Introduction of non-native species is a costly practice by uninformed fishermen who want to bring the fishing experience of one body of water to another that is typically more convenient or local. More needs to be done by biologists to inform the public of the long term detrimental factors of such practices.
    It’s happened to numerous lakes when pike are discovered but also, aquatic plants have been transported and introduced into lakes by fishermen who think they are making improvements. The effects to native habitat by invasive plants, not to mention all of the hitch hikers attached to them, needs to be discussed so that the public can be informed and hopefully discouraged from making these critically damaging decisions. Please generalize this discussion to cover all freshwater bodies of water so as to inform, discourage, and hopefully prevent future harmful introductions.

  3. Well, it won’t take long now for some environmental group(s) and idiot politicians like Bernie and AOC to proclaim that the entire park needs to be closed off to humans.

  4. Those fish can be transported by birds, weather and high water, plus its nearly impossible to make sure you get them all, I would say quit wasting money on it and mitigate the damage with fishing rules and special seasons

    1. Please cite a source. Trout eggs are adhesive for a few minutes before being buried in gravel. I have worked on trout conservation for decades and have never seen evidence of this. If birds were a dispersal mechanism of fish eggs, we would have no protected refuges for native fish. It’s an absurd assertion.

  5. Remember you are not God. Stop interfering in nature. Haven’t humans done enough damage to it.where is it written that only certain fish shall be in certain places let it go .killing one fish over another isn’t that racist.

  6. Brooke trout is a damn good eating fish and they can do some serious fighting like a lake trout. Why don’t y’all catch them and eat them good God y’all wasting some good fish I just don’t understand why?

  7. It is possible that a bird was flying with a fresh caught fish and dropped it in flight. It actually happens quite a bit . That’s how many species came to be and thrive in different water ways. That’s entirely natural. Man should quit messing with it .

  8. Seems to be over kill to poison an entire creek over a dozen unwanted fish. The poison kills everything that comes in contact with it. It could take years for the food sources and other biological habitat to return to support a thriving fish habitat. You would think there would be a better way to deal with the invasive fish.

  9. There is always the Lone Natrualist, who is obviously not researching community & standing at the boundaries of non socializing. I.E. Character types. Who operate with an obstinate attitude. Which is unfortunate for those who are doing and taking action necessary. To recover a indigenous species before it is lost? Obviously greater or more effective forms of communication? Are required to allow the overall goal. To be achieved without polluting the DNA. Thus restore the natural habitat, to its original state. Feel free to make appropriate edits.
    D.M. Morris

  10. Like the one guy said do you ever think about birds being the animal that bring them back all it takes is a bird flying over a watershed and dropping there catch in a different watershed if the fish is still alive it will find its way there bookie if they was born there they will go back there like any other fish will go back! You are not allowed to keep a cutthroat because in a native fish! But what about the people that was Born in the state they are native! But if my ancestors was born here then I could keep the fish to eat! And I never keep fish anyway because I fish with barbless hooks and if I have to cut my line with out taking the fish out of the water! I do believe that every animal that live on earth has a right to live here! Every animal!

  11. More waste of time and money. How much are these fools getting paid to do this. Everyone should be fired and have to get real jobs.

  12. If it is, indeed some human introducing brookies, I hope the person/s are caught! Ultimately, it’s the wildlife, land, air and water that suffers. A BIG shout out to the women & men of Wyoming Game and Fish doing their best to protect & manage our greatest heritage and inheritance of the future generations to come, this place we call home.

  13. Brook Trout eggs can stick to birds feet such as Herons, Egrets and shorebirds. In this manner be carried to different water sources.

  14. I don’t like the idea of killing one trout for another, especially since Brook Trout are often a soft target among fishery managers and anglers. . Look at what is happening with Browns in Wyoming. Should we ignore those losses in what is, after all, an invasive species? Odd, inconsistent logic in fishery management.

  15. I’ve seen high mountain lakes with healthy brook trout populations destroyed by biologists planting cuttroats. They say bigger fish bring more tourist money. There are plenty of cutthroat streams and lakes already. I grew up fishing and eating brook trout, as did my children and grandchildren. Catching a big fish is an absolute joy but I wouldn’t eat a cutthroat, rainbow, or lake trout. One exception is cuttbows, which are delicious. Please leave brookies alone!

  16. Hi I’m a fly fisherman but won’t pretend to know much about the different fish my question is why don’t you want the brook trout in there?

  17. If they track down this person/ persons tampering with Nature, fine them $100,000, and 5 years in prison! Make it prohibitive!

  18. There are lots of rivers that have both species. The whole obsession/ paranoia with “invasive species,” is a huge waste of money and time. I have fished plenty of streams that contain both species and there are hundreds of streams where these two co-exist. They will be fine. You are worried about an unlikely guy with a bucket but not about dumping poison in the river, electro shocking cutthroat, killing the food sources in the stream, closing the river so you can play fish god?
    Meanwhile, more thousands of streams are ruined by dewatering to grow hay. The money you are wasting can go to paying ranchers to leave water in streams, saving all species.
    The giant freak out about Bull Trout is another costly fetish. There are plenty of them. Doesn’t matter if they are basically useless as gamefish and voracious feeders on all types of other trout and inedible, they get all the $$ because they are “native.” They won’t be fished out because no one wants them.
    Keep our streams full of healthy trout, and encourage those that are the best suited for a particular waterway.

    1. 100 0/0 ,all the science or politics or fish biology cannot be good for anything except an ego,maybe. We have native streams on eastern side of USA as well. Our trout streams are over ran with native and non native fish, if you really cared you would know that poison in any habitat is not going to fix anything. Most biologists are only trying new things and most of it doesn’t work. In western NC the forest service cut all grape vines off at ground level ,what eats grapes, everything in the woods. It is trying to be God and it will not work.Good luck

    2. Your comments are a case of ” what about issum ” you stated no scientific evidence of your hypothesis just gut instinct . The people involved in this project represent 10s of thousands of hours and many years of research.

  19. Makes no sense to me. The areas outside the park are cram full of brookies. I think they find a non human way of getting back into the creek. It would seem doing the same thing will result in the same result.

  20. I know fish eggs can also be carried by birds that wade in shallow embankments to feed. The eggs can get caught in the feathers and can actually stay moist long enough to travel with the bird to a new body of water.

    I recognize that native species can indeed be negatively affected by other species, but I can’t help but wonder if there are other ways to balance those ecp systems without poisoning the water. Do we truly understand the impact of the poison on all aspects of the ecosystem at play here?

    1. Please cite a source. Trout eggs are adhesive for a few minutes before being buried in gravel. I have worked on trout conservation for decades and have never seen evidence of this. If birds were a dispersal mechanism of fish eggs, we would have no protected refuges for native fish. It’s an absurd assertion.

  21. We’ve had the same problem at a lake by Laramie. Someone with no water rights has introduced bass. This will probably happen more often as ranches are turned into developments.

    1. There is more to fish than just being your favorite species to catch. Cutthroat trout native to a drainage fulfill an important link in the evolutionary chain that developed around their presence. I would think, as a devoted angler, you’d appreciate the restoration of a species that once occupied that habitat for hundreds of years. Their presence and preservation makes the angling experience for them unique and “historic”.

  22. Let’s not forget that fish know how to swim,and they could have put them selfs right where they were found. Unless of course the stream is self contained?

  23. This truly is bad news; not because someone might have committed bucket biology, but because a very valuable conservation population of native Yellowstone cutthroat trout is again under threat from a prolific invasive. I applaud YNP fisheries crews for jumping on this and doing everything that they can to find and remove these fish. Bucket biology is an extremely dangerous example of personal greed and interference. As pointed out, it should be dealt with immediately and harshly. What is most concerning to me is that some (as evidenced by the comments) don’t seem to understand the importance of our native species of fish to the ecosystem. Natives help support the balance that nature intended. Invasives upset that balance. This isn’t about whether we as anglers can catch a certain species. Removing these natives is expensive as witnessed by the costly efforts on Yellowstone Lake. We’re fortunate that YNP fisheries managers and the upper administration recognizes the importance of our native fish and is willing to spend what it takes to restore and maintain them. To them I say “Thank you!”. Now the rest of us who represent the vast majority should do our part to support them.

    1. Spot on. Invasives upset the balance of nature, up and down the food chain. I hope they catch the person who did this.

      1. Yes. Get of all invasive species. Especially the worst ones, humans and cows… wtf people. The ecosystem is burning down and we are fighting brook trout? And just how did the brook trout get there from the Appalachian mountains? Those pesky humans and the Park Service. Like the lake trout. Meanwhile the Wyoming Game and Fish keep stocking non-native Frankenstein rainbows everywhere to keep their hatchery employees busy. None of it makes sense.

    2. There is no “balance in nature” as yall are describing. It is an always and forever evolving landscape. Just because a pasttime specie of your youth is no longer the dominant of the area doesnt mean you should be slaughtering animals lives for the purpose of reinstating your personal preference.

      Hilariously, believe it or not, your so-called “native” cutthroat were the invasive species. And there was a different one before them
      And before them another. So just because you have a recorded history of 100 years under your belt, stop pretending you know whats native and what should go or stay. Time is been passing by for EONS before your conservation group was formed. Tens of thousands of species have most likely called these waters home at one time, and eventually lost ground to a new specie. Thats evolution.

      Unless its a case of clear human destruction, like with the American Buffalo, this kind of conservation is more than just unnecessary, its dangerous to the entire ecosystem. We are preventing natural selection from taking place, thus creating weaker and weaker gene pools. Let animals fight and be strong, not weak and nurtured by man.

  24. Very nice article… Thank you for writing it … I live in the western basin of lake Erie and we are having issues with invasive snake head fish 🐟… I appreciate the time you took to write the article..

  25. If it is illegal stocking, it’s the height of selfishness. I mean, a guy can catch brookies anywhere and everywhere up around Cooke City. More brook trout than stars in the heavens. But with pure strain cutthroat, it’s another matter altogether. They are rare indeed. Yet these type of individuals think only of themselves. Wyoming has the toughest illegal stocking laws in the nation, including a lifetime ban on hunting and fishing. If they ever catch some bucket biologist, I hope they make an example out of him and take his privileges for life. This has to be stopped.

    1. Yellow brook trout are none native and can eat large quantities of Cutthroat, a native species.
      They breed at different times of the year giving the brook trout an advantage as their young eat the cutthroat embryos.

      1. This comment is the only substantive one concerning the issue of removing the non-native brook trout. Others simply ‘claimed’ it was a bad thing. That being said, sometimes I think this native/non native focus is overblown and doesn’t recognize ecological change, supposing that our environment is static. It is not. It is always in motion. Species cease to exist.

        From the American Museum of Natural History we read: “Scientists estimate that 100 to 10,000 species — from microscopic organisms to large plants and animals — go extinct each year.” However, the same article stated, “This is 100 to 1,000 times faster than historic extinction rates. Species can become extinct when humans over hunt and over fish, pollute the environment, destroy habitats , and introduce new species to areas.”

        Given what was said about spawning times, if true, the action taken seems justified.

  26. When considering how the brook trout got there, don’t forget that there are likely National Park contractors and employees who may benefit financially from this work.

    1. Exactly! These “fishery” workers would be out of work if the non native fish were not in the waters. They have all the incentive to keep this scam going forever

      Fishermen can catch Brooke’s anywhere; they don’t need or want them in this creek

      1. According to the article there’s a particular person, well known to the fishery workers – and a non resident of the State – who opposed the original removal of Brookies from the creek. (Probably a guy who bought a vacation property, and thinks he bought the creek as well.)

    2. We were just discussing the fact that Sunlight Creek (where brook trout were poisoned several years ago—and where we went a number of subsequent summers without seeing a fish of any kind) is once again teeming with brook trout. Curious about what the biologists attribute this resurgence to?