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  1. #1
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    Feb 2019
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    Blue Ridge, Rappahanock, Potomac and Fingerlakes Region
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    Default Taking the temp of the water in a mountain stream

    Ok still wearing my newbie cap I thought that I'd throw this question out there. I have been told in both fly fishing classes as well as read in several books that trout really become active in mountain streams where I will be fishing once the temperature of the water hits 40 degrees for 4 consecutive days. So trying not to over think this but since temps fluctuate by a wide margin in the spring, sometimes 20+ degree swings in a single day, does it matter if the water temp hits 40 degrees for only about an hour a day , i.e. that's the high temp for the day and all of the rest of the day its in the 20's and 30's or is this a thing like it needs to be 40 or above consistently for 4 days? Again I hope that I'm not over thinking this. Any insight here would be great. Thanks.

  2. #2
    Join Date
    Oct 2012
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    Default Re: Taking the temp of the water in a mountain stream

    Interesting question.
    I've only really thought about what the temperature is 'now'. Fish take on the temperature of the surrounding water very quickly.
    If it's a situation where the fish move a good distance based on the water temp, then I'd guess the temperature over time would matter more.
    Today is the first day of the rest of your life.

    Paul

  3. #3

    Default Re: Taking the temp of the water in a mountain stream

    Trout become active when their food--the bugs--becomes active. That's not when the water hits any particular temperature, rather it's when a certain (for each species of insect) number of degree days have accumulated. So it's actually a somewhat broader measure than just hitting 40 degrees for 4 consecutive days. It depends on what the preceding days have been like.


    On the streams you fish, hitting 40 degrees for 4 consecutive days may be a reasonable way to guess that things are heating up, but I've seen fish rising heavily in water that was frozen at the edges. So it really depends on the stream and the bugs. You just have to get out there and keep checking
    Zackdog lives.

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  5. #4

    Default Re: Taking the temp of the water in a mountain stream

    Here's two quick reads that may help expand understanding albeit requiring piecing together semi opposing takes:

    Trout and Water Temperature: How Hot is Too Hot? | Hatch Magazine - Fly Fishing, etc.

    Trout & Temperature – Tenkara Talk


    As other's have stated, the ambient and water temp fluctuations may elude to increased or decreased fish and insect activity, but is not the end all, be all, to base your fishing parameters around.

    Further, water temp has an effect on oxygen content as well, and as ethical sportsmen, we have a responsibility to not overstress trout when their health and potential propagation is at risk, I think many overlook this aspect, of not fishing when trout are already struggling to make it through warmer water conditions during peak ambient temperature periods.

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  7. #5
    Join Date
    Feb 2019
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    Blue Ridge, Rappahanock, Potomac and Fingerlakes Region
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    Default Re: Taking the temp of the water in a mountain stream

    [QUOTE=cooutlaw;1318834]Here's two quick reads that may help expand understanding albeit requiring piecing together semi opposing takes:

    Trout and Water Temperature: How Hot is Too Hot? | Hatch Magazine - Fly Fishing, etc.

    Trout & Temperature – Tenkara Talk


    As other's have stated, the ambient and water temp fluctuations may elude to increased or decreased fish and insect activity, but is not the end all, be all, to base your fishing parameters around.

    Further, water temp has an effect on oxygen content as well, and as ethical sportsmen, we have a responsibility to not overstress trout when their health and potential propagation is at risk, I think many overlook this aspect, of not fishing when trout are already struggling to make it through warmer water conditions during peak ambient temperature periods.[/QUOTE]

    Cooutlaw,
    Very interesting, Thanks for the links. Now help me understand what you mean by the italicized bit above.

  8. #6

    Default Re: Taking the temp of the water in a mountain stream

    Quote Originally Posted by City Rat View Post
    Ok still wearing my newbie cap I thought that I'd throw this question out there. I have been told in both fly fishing classes as well as read in several books that trout really become active in mountain streams where I will be fishing once the temperature of the water hits 40 degrees for 4 consecutive days. So trying not to over think this but since temps fluctuate by a wide margin in the spring, sometimes 20+ degree swings in a single day, does it matter if the water temp hits 40 degrees for only about an hour a day , i.e. that's the high temp for the day and all of the rest of the day its in the 20's and 30's or is this a thing like it needs to be 40 or above consistently for 4 days? Again I hope that I'm not over thinking this. Any insight here would be great. Thanks.
    I'm a bit confused by your post. As a newbie, I think you might have some temps mixed up.

    First of all, how can the temperature of water in LIQUID form in the 20's since water in a stream is fresh water freezes at 32 degrees or below? Salt water or water under high pressure can get below 32 degrees and still be a liquid but this is not in the situation you mention.

    Secondly, trout are lethargic at low temps and at 40 degrees, I would think they would be very lethargic. I don't understand how books could say that trout become "active" when temps hit 40 degrees.

    The only situations where I have seen trout to be "active" is when the water temps are CONSTANTLY low. For example in bottom draw tailwaters like the San Juan where the water coming out Navaho Dam varies from 39 - 46 degrees. On the San Juan the trout just below the dam have adapted to these low temps and will feed in 40 degree water.

    https://www.sciencebase.gov/catalog/...b07f02db51cbfb

    Are you sure the temperature was not 50 degrees instead of 40 degrees for these mountain streams. The 50 degree temp would conform to what is usually taught. See:



    http://flyfishing-and-flytying.co.uk...es_of_success/

    Using Water Temperature in Locating Fish | Encyclopedia.com

    Optimum Water Temperatures for Fly Fishing - dummies

    Why Water Temperature Plays a Role in Your Fishing Success

    http://flyfishing-and-flytying.co.uk...es_of_success/

    I am willing to learn when I am wrong so if you have references to which books say trout “really become active” at 40 degrees in these mountain stream, I would appreciate it.
    Regards,

    Silver



    "Discovery consists of seeing what everybody has seen and thinking what nobody has thought"..........Szent-Gyorgy

  9. #7
    Join Date
    Feb 2019
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    Default Re: Taking the temp of the water in a mountain stream

    Super interesting, Yes I am sure that it was 40 degrees for 4 consecutive days , I sat in the class last Saturday and we were all told this very very clearly. Now Once I get home I will find the reference in the book and let you know. I will note the class is very localized to fly fishing for wild trout in the local mountain streams near here so there is a chance that this is a local species adaptation.

  10. #8

    Default Re: Taking the temp of the water in a mountain stream

    [QUOTE=City Rat;1318911]
    Quote Originally Posted by cooutlaw View Post
    Here's two quick reads that may help expand understanding albeit requiring piecing together semi opposing takes:

    Trout and Water Temperature: How Hot is Too Hot? | Hatch Magazine - Fly Fishing, etc.

    Trout & Temperature – Tenkara Talk


    As other's have stated, the ambient and water temp fluctuations may elude to increased or decreased fish and insect activity, but is not the end all, be all, to base your fishing parameters around.

    Further, water temp has an effect on oxygen content as well, and as ethical sportsmen, we have a responsibility to not overstress trout when their health and potential propagation is at risk, I think many overlook this aspect, of not fishing when trout are already struggling to make it through warmer water conditions during peak ambient temperature periods.[/QUOTE]

    Cooutlaw,
    Very interesting, Thanks for the links. Now help me understand what you mean by the italicized bit above.
    Well, if you read the first link, you will note that trout suffer to maintain sufficient oxygen once temperatures rise above their natural tolerance, this affects not only their ability to grow, gather food, maintain health in general, which could ultimately lead to death and not being able to spawn or perpetuate the species. Anglers that fish trout in extremely warm water at the peak of summer temps are putting them in greater jeopardy of perishing after they extend the energy and oxygen during a catch, which ultimately lowers their survival rate after release. Hence the reason trout in lakes are at deeper (cooler) depths during the height of heated months. If the water temp is at or nearing their peak tolerance level, the ethical thing to do is call it a day and go home...let them have a better shot at living for another day.

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  12. #9
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    Feb 2019
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    Default Re: Taking the temp of the water in a mountain stream

    Thanks for the explanation. That makes perfect sense.

  13. #10
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    Default Re: Taking the temp of the water in a mountain stream

    I've never heard the "40 degrees/4 days" thing, so I can't really comment on that. Other than to say that ambient air temp and water temp are two completely different things. Air temp may fluctuate by 20 or more degrees during the day, but water takes a lot longer to change temp significantly. So while the low air temp might be 35 and the high ends up being 75 over the course of a hypothetical day, the water temp won't change much over the course of that same day, so it was 45 at dawn, it's likely to be within a few degrees of that by nightfall.

    What I have heard and have found to be fairly accurate, is that several days of similar weather (pretty sure I read three days) will lend itself to better fishing. In other words, when I look at weather, I want to see at least three days of roughly the same temps, weather conditions, etc. before the day I think I'm going fishing. Most of the time the fishing seems more predictable on that fourth day.

    For instance, about three years ago I was fishing in WY (I know, there's no fish there), and every day was the same. Sunny and relatively warm in the morning, light breezes. decent but not strong feeding activity.

    About 3pm everyday there was a thunderstorm that rolled through, dropping temps by as much as 15 degrees, high winds, and of course heavy cloud cover. After 3 days the fish seemed to know the storm was coming. They began to feed more heavily as the clouds rolled in and shut off about an hour after. Feeding again picked up about two hours or so after the daily storm rolled off to the north. Air temps were extremely consistent except for one day when the storms rolled in really early and stayed all day. Fishing was sporadic all day and into the following morning until after noon.
    "Three-fourths of the Earth's surface is water, and one-fourth is land. It is quite clear that the good Lord intended us to spend triple the amount of time fishing as taking care of the lawn." ~Chuck Clark

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