Effects of heat on a cold-water fishery

The Forum is Closed. Forums The Ecology Effects of heat on a cold-water fishery

This topic contains 3 replies, has 4 voices, and was last updated by  msbfly 5 years, 2 months ago.

Viewing 4 posts - 1 through 4 (of 4 total)
  • Author
  • #541

    Dry Fly Guy

    This is a companion post to my post in The Cast section titled: Warm Water.

    I was taught as a child back in my spin casting days that when the water gets too warm, the oxygen levels in the water drop, and fishing for trout at those times causes undue stress on the fishery, so don’t do it if you aren’t keeping what you catch. 67° F is the arbitrary temperature limit that has stuck with me, but probably because as a little kid I could easily remember it by counting “six, seven.”.

    I won’t tell you that I have never fished for trout when the water temps were higher. I probably have, even if I didn’t know it at the time. But up until about four years ago, I really didn’t even carry a thermometer. I just stuck a hand in the water and thought, “that feels a bit warm” or “Brrrr, that’s cold.”

    So for all you fishery management experts out there, my question is this: What does the real science behind water temperatures say, and generally speaking, at up to what water temperature can us dry fly fishermen safely fish Catch & Release for trout?

    ~ DFG


    Eric Peper

    Personally, I think it’s probably 70 that’s the critical temp. A few weeks agp, the water coming into the Henry’s Fork from Island Park reservoir was at 67, and there was no deleterious effect of which I’m aware. That water is cooled by springs and tribs, so perhaps it isn’t a good measure.

    I didn’t take a temp in the Madison in YNP two weeks ago, but I wish I had. My wife and I fished it, and I spotted a nice fish for her. She cast and caught it, and it took me 10 minutes to revive it. We left the river right after that. I have no idea why the National Park people hadn’t closed it.




    I fish all summer long, usually I’ll look for better oxygenated water when water temperatures are way up. The indicator for me is not the exact water temperature (even though at 70F, experience tell me that most of my waters will be out of the question) but the rate of recuperation of the fish at the release. If it takes more than a few minutes to recover the fish, I’ll no longer enjoy my self catching them. The white water parts of the rivers are usually still fishable at higher water temperatures.
    Luckily I live close to a very large and deep lake where it rarely (ever?) hits 70F. The lake fishing for grayling and the water temperatures in local streams usually peak at the same time…



    Obviously temp is a major factor. The higher the temp, the less oxygen in the water. I feel the shorter the fight the better. If I am in fast water it will take longer to land the fish and the more the fish has to fight the more stress it has on itself. Combine that with high temps…I will pass on fishing that river.

    I made a decision to not fish in water temps above 65 degrees. I have done little reading on this topic but what I found was 70 degrees was a “standard” or “norm”.

    So I raised, or lowered? the bar for my personal guidelines for such situations. I don’t want hurt a resource I enjoy when I can find somewhere else to go.

Viewing 4 posts - 1 through 4 (of 4 total)

You must be logged in to reply to this topic.