Riainbow or steelhead?

Discussion in 'Steelhead' started by Smalma, Sep 3, 2007.

  1. David Dalan

    David Dalan 69°19'15.35" N 18°44'22.74" E

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    Keith,

    I'd be happy to fish with ya! My unlce and some of his cronies frequently pine about the things you used to be ablet to do in the "old days" (Chinook fishing on the Wenaha, steelhead in the little Walla Walla and Dry creek, etc.). Things are still pretty good...IMO :)

    Shoot me a PM or just look me up in the local yellow pages if you think your heading in.

    Andy and I have some common fishing partners, but I have not personally fished with Andy.
     
  2. Paul Huffman

    Paul Huffman Lagging economic indicator

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    I thought group selection as a theory was pretty much out the window, except in some very narrow theoretical situations.

    Kin selection is likely still, but is quite a bit different than "A strategy that makes little sense for an individual may be key at the species level." Do you have an example of what you mean? Will I finally find a answer to my struggle to understand the evolution of the strategy of "displacement flights"? http://www.washingtonflyfishing.com/board/showthread.php?t=15543&highlight=displacement+flights
     
  3. Smalma

    Smalma Active Member

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    Paul -
    I guess the best example that I can think of off the top of my head would the one I referred to earlier - that is the spawning timing of our wild steelhead. In this case lets use the wild fish of the Sauk.

    They have some of the latest spawning in the State with peak spawning happening the 2nd and 3rd week of May. With that spawning timing the fry typcially leave the gravel around the first of August; several weeks later than say the Skykomish. A quick look at the hydrograph of the Sauk sheds light on the likely reason why that would be. Typically (at least in the past) the snow run-off last well into July or even early August. For the fry to pop out of the gravel earlier would place them in harms way to those high flows ( the daily average flows in June is higher than even during November the typical flood month here in western Washington). Having the spawn timing matching up with the environmental factors only makes sense and if find it pretty cool.

    However every year there are some very late spawning fish in the Skagit basin. Common to see some spawning June and even July (a couple of times actively spawning steelhead have been seen as late as the last week of July). The timing of that spawning makes little sense. Even with elvated summer temperatures those late spawning fish would not be emerging from the gravel until late August or even early September. That is so late in the growing season that those fry would be exceptional small and have little fat reserves when compared to the earlier emerging fry. That would be a very key issues for over-winter survival - those smaller fish would be strongly selected against.

    The question becomes why in the heck would those late spawning fish presist in the population if the fry are at severe selective dis-advantage? The answer I believe is that on years of very high snow packs and/or late run-offs the high run-offs last well into August placing those normal timed fish in harms way. However those fry from late spawning fish would be prefectly timed to escape the high flow mortalities. Thus while most years being from a late spawning parents is disadvantage and makes poor survival sense occassional the pay off from being a late emerging fry must be enough of an advantage for that behavior to presist in the overall population.

    While I agree that all the above is merely speculation on my part and probably does not "prove" anything in the classical sense. It makes good sense to me and seems to explain a puzzling behavior.

    Tight lines
    Curt
     
  4. Paul Huffman

    Paul Huffman Lagging economic indicator

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    Yes, but that's an example that's straight adaptation. Every five to ten years those late timed fish do real well. Their progeny return and the late timing trait is preserved in the population. Some years it's the early timed fish that reproduce most successfully and the early timing trait is preserved in the population. Still the individual fish and their selfish genes are programed only to do the best they can at reproducing. There's no selective pressure trying to preserve the species.