Cutthroat rapidly losing out to lake trout in Yellowstone Lake

Cutthroat losing out to lake trout in Yellowstone Lake. Native trout numbers lowest since counting began. By Mike Stark. Of The Billings Gazette Staff.

The situation is more dire than I thought possible. It is a catastrophe for Yellowstone wildlife and all those who enjoyed fishing the tributaries to the lake. Those is in boats, who fish deep, may not be as unhappy.

It appears to me from what I have read, that the introduction of the voracious lake trout, which does not make itself available to surface predators because it lives deep, was an accident resulting from fighting the 1988 Yellowstone Park forest fires. That’s about the date (1988) nailed down for the oldest Yellowstone Lake, lake trout.

The firefighting involved large helicopters dipping huge buckets into the lakes and pouring them on the fires. Nearby Lewis and Heart Lakes had no trout before the Park was established. Lake trout were stocked in them.

Because Lewis Lake is close to Yellowstone Lake and fires were raging the in subtle topography around and between the two lakes, I think a helicopter dipped water from Lewis Lake (with lake trout) included, and dumped it in on a fire in a tributary of Yellowstone Lake. A few lake trout survived and took up residence in West Thumb, the part of Yellowstone Lake closest to Lewis Lake. This is also the place where high lake trout numbers were first observed.

I had thought the Park’s deep net fishing for the lake trout in Yellowstone Lake was making progress, but apparently not, despite pulling in thousands of lake trout.

The lake trout eat the cutthroat trout. The cutts feed at or near the surface, and make spawning runs up creeks to lay their eggs. This used to be of great importance of many kinds of Yellowstone wildlife. The lake trout are born, live and die in the deep.

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  1. TPageCO Avatar

    If I remember correctly, recent testing of lake trout has determined that the source of the invasion was not the 88 fires. Genetic tests revealed several different times when lakers got in the lake, and various sources for the fish, which most likely points the finger at bucket biologists. If I can find the report, I’ll see if I can send it to you.
    It doesn’t make the problem any less bad, though.

  2. Ralph Maughan Avatar

    I got my idea about this from Yellowstone Science. Spring 2006. The article is “Where Did They Come From? Natural Chemical Markers Identify Source and Date of Lake Trout Introduction in Yellowstone Lake.”
    That’s how I interpreted the article, but I didn’t reread it before I posted this morning. Now I’ve read it again. They [in the article] concluded that it was almost certain that the lake trout came from Lewis Lake and the number was fairly large, they seemed to state that the transfer was unauthorized, meaning not accidental. Actually it might have been multiple transfers. To quote:
    These results therefore support the assertion that initial transplanting and natural reproduction of lake trout in Yellowstone Lake likely occurred during the mid- to late l980s (Kaeding et al. 1996). Although our sample size was not large enough to pinpoint the exact number and timing of transplants, Ruzycki et al.’s (2003) estimate of 298 lake trout > 10 years old in 1996 (year-class 1986 and earlier) suggests that a rather large number of individuals were transplanted. Moreover, the dating of the abrupt shifts in otolith chemistry as occurring in 1989 and 1996 suggests that multiple transfers may have occurred.
    The classification of 90% of the early-growth-zone Sr:Ca ratios of the suspected transplants into Lewis Lake by discriminant analysis suggests that of the two lakes considered to be the most probable source lakes within Yellowstone National Park, Lewis Lake is the likely source of transplanted lake trout. Unlike Heart Lake, Lewis Lake is accessible by road, which may have facilitated the unauthorized transfer of lake trout into Yellowstone Lake.

  3. TPageCO Avatar

    Hmmm….here’s something from the NPS Yellowstone Fisheries and Aquatic Sciences Annual Report from 2005:
    “…lake trout – a species illegally introduced to Yellowstone Lake at least 20 years ago…” This would suggest a pre-1985 beginning for the transplants.

    This isn’t the report I was looking for, but it’s written by Todd Koel, the guy cited in the article. In regard to the likelihood that a large # of fish were transplanted, I think the odds are against big numbers of lake trout being near the surface in August and September of 1988 (they live deep in the lake, particularly in hot summer), where they would be scooped up by the water buckets. More likely, someone wanted to catch big lakers and recognized that the lake cutt population would provide a great food source to grow such fish. It follows that such a person/persons would spend the season (seasons) transporting enough lake trout to make it happen.

    Let’s hope it can be contained over time. Everyone thought whirling disease would decimate western streams and most seem to be recovering well, even hard-hit areas like the Madison and the Black Canyon of the Gunnison. Money to fight the laker invasion has been coming from lots of sources, which is encouraging too.

  4. Jim Rosenberg Avatar
    Jim Rosenberg

    Ralph, thanks for the update. Very sad news indeed! I fished Clear Creek and Beaverdam Creek along the eastern shore in the Summers or 1974 and 1977. Clear Creek held big Cutts behind almost every rock and was a sight to behold. To imagine that this fishery is almost void of fish is almost incomprehensible. I too was hoping that the gillnetting efforts were helping the situation and the population Lakers could have at least been kept in check. It is sad to think that we won’t ever see anything like it was in the past regardless of how the Lakers were introduced. Anyway, thanks again for the update – I was hoping for better news as I was hoping to return there with my two sons so they could experience something like I had done. It is a shame it will only be memory!


Dr. Ralph Maughan is professor emeritus of political science at Idaho State University. He was a Western Watersheds Project Board Member off and on for many years, and was also its President for several years. For a long time he produced Ralph Maughan’s Wolf Report. He was a founder of the Greater Yellowstone Coalition. He and Jackie Johnson Maughan wrote three editions of “Hiking Idaho.” He also wrote “Beyond the Tetons” and “Backpacking Wyoming’s Teton and Washakie Wilderness.” He created and is the administrator of The Wildlife News.

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Ralph Maughan