Temperature salmonflies need to hatch
Does anyone know the temperature salmonflies need to hatch? I've read mid-50s over and over, but that doesn't make any sense cuz it hits the mid-50s on many salmonfly rivers here in sw montana in april, and the big guys don't come off til June. But everyone says the temperature plays a big role in when they hatch. I'm confused....
Salmonfly Hatch and Temperatures
Josh -
Not sure of the temperature range that is most conducive to this hatch, but anecdotally, from this neck of the woods, water temperature is definitely a factor. Consider the following.
The salmonfly hatch on the Henry's Fork is just about over.
The salmonfly hatch on the South Fork of the Snake won't get started for several weeks, sometime around July 4, traditionally.
The Henry's Fork runs warmer temps through the spring and early summer than the South Fork which accounts for the early hatch on Henry's Fork and much later salmonfly hatch on the South Fork.
Happened to have coffee just a couple days ago with one of the top guides in our area and he was commenting on this very subject, and confirmed the above.
Another tidbit about the effect of water temperature on the hatch, is that in most places this hatch moves upstream up to several miles a day. The point being that the water temps are typically higher downstream and increase incrementally on a daily basis as the overall weather patterns, length of daylight hours, and air temps improve / increase.
John
The fish are always right.
Degree days and water temperature
SquatchHunter-
All aquatic insects require some particular thermal regimen in order to mature. This is customarily measured in degree days. You can probably search the archives of this site for an article by the Stream Doctor, which will provide a more complete explanation of this principle. In any event, a Salmonfly nymph requires 2-4 years to acquire the thermal regimen necessary for maturity. Once that maturity has been attained, a specific water temperature does seem to trigger emergence, and that is likely the mid-50's to which you refer. Hope this helps.
Roger Rohrbeck
www.FlyfishingEntomology.com
Roger -
Just followed the link to your website and wandered around in there for a while.
Very nicely done, and lots of really good / helpful information.
John
The fish are always right.
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