Warm water due to hot weather, not hot springs, killing Yellowstone Park trout

With the record high temperatures in the Rocky Mountain and Intermountain West, the temperatures of trout streams are soaring above, sometimes far above, that which kills trout.

It is plainly evident in Yellowstone Park. Heat kills fish in Yellowstone. Jackson Hole News and Guide. Yellowstone is more vulnerable than many mountain stream areas because the hot springs do raise the stream temperatures over what is common at the elevation and the Yellowstone is mostly a high plateau, not an area full of snow-capped peaks.

Trout and other fish are under heat stress in many other places too, with their mortality not getting in the news like it does in Yellowstone Park.

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  1. Mike Wolf Avatar
    Mike Wolf

    I wonder how much of this is because of riparian damage in grazing allotments.

    Riparian areas provide much needed shade for headwater and other spawning streams. Damage to these riparian areas by ungulates both native and exotic (livestock) can drastically reduce shade on the streams and both increase the temperatures, and increase the algae, choking out trout.

  2. Mike Lommler Avatar
    Mike Lommler

    Seeing as how this article concerns the park itself, livestock is probably not a big issue. It likely is an issue outside the parks. In the park itself some of that native ungulate damage should be at least moderated by the presence of wolves keeping them in the open and on the move–riparian cottonwoods and aspens have been recovering.

  3. Buffaloed Avatar

    This will likely be the case for Idaho’s salmon this summer. The low water, total lack of snowpack, high temperatures, all combine to reduce the oxygen content of the water. The large size of the salmon accentuates this problem because they have less surface area/body weight to absorb oxygen. All of this reduces the immune system of the fish and fungus can cover their whole body and kill them before they spawn. This is even more common if the fish has any open injuries from predators or a fishing season, also nitrogen burns from super-saturated water at the dams cause large blisters on thier head and sides (it’s the same concept as the bends in divers).

    Spawning is usually triggered by lower temperatures that come at the onset of fall in the high country, usually in mid-August until the second week of September. That means the fish have to find a suitable place to hide and escape the high temperatures for another 5-6 weeks which will be the toughest weeks of the summer.

    Presently the fish’s eggs and milt are packed solidly in their bodies so they can’t spawn early and, if they did spawn early, their young would emerge from the gravel too early in the spring before there is enough food available for them to survive. It all has to do with degree-days which refers to the number of temperature units above a certain temperature accumulated over a period of time. It takes less time for the fish to grow in warmer temperatures than in cooler temperatures so if the fish spawn early their eggs would experience more degree-days and thus develop early.

    It seems we are screwing them from every angle if you factor global warming into the equation. The dams kill them on each end of their journey. It’s like a war of attrition. There have been years on a particular river where I have documented at least a 40% pre-spawn mortality among wild chinook, and the big 5-year-old (3 ocean) females are the hardest hit (less surface area/body weight again). That means that there are fewer eggs in the gravel for the following spring making recovery harder.

  4. Ralph Maughan Avatar

    Livestock in most of the West trample the banks of streams, causing the banks to “calve off,” slowly widening it and making it shallower; thus, easier for the sun to heat the water.

    The problem is greater with creeks than with rivers.

  5. Mark McBeth Avatar

    It is unfortunate that the Park Service offered only an advisory on the Firehole, Madison, and lower Gibbon. All three of those rivers should be closed to fishing for the summer like they were in 2002 and 2003. The Park Service claims that they are being responsive to user groups but no ethical fly fisherman would dare try and catch fish that are struggling to survive in water that is regularly hitting 80 degrees and higher. There was no outrage in 2002 and 2003 and the fly shops in West Yellowstone all normally actively discourage people from fishing the Firehole after July 4th. The decision to issue an advisory and not a closure appears to be part of the please the consumer philosophy that has guided the Park Service decision making the past 7 years.

    Finally, I noticed on the USGS data that the water level in the Firehole is running at levels consistent with record low flows in 1988 (224 CFS on July 8, 2007, 225 CFS on July 8, 1988). You can also track the temperature on that data base (http://waterdata.usgs.gov/mt).

  6. mikarooni Avatar

    I can see it all now. The 2027 national televised bass hoohaw tour will include the Yellowstone Rubber Worm Jigging Pro Tournament, sponsored by Koors Lite, NASKAR, some strange brand of flavored snuff, and Jimmy Dino Sausage of course.

  7. mikarooni Avatar

    …but there’s no such thing as global warming. It’s just getting really hot is all.


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