Bad actor suspected in Yellowstone brook trout discovery
FROM WYOFILE:
Scientific evidence still lacks, but signs point toward an illegal introduction of nonnative trout in already restored Soda Butte Creek.
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.
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.”
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.”
WyoFile is an independent nonprofit news organization focused on Wyoming people, places and policy.
This story was posted on August 10, 2023
