Friday, April 6, 2012
Fly Friday: Mastering water temperature trends...
Trout being cold blooded critters as water temperature trends upward toward (or downward away from) the ideal (60 degrees give or take a couple depending on species) so goes metabolisms and....And thus go our fishing propects.
Given water temperatures hovering in the mid-30s to mid-40s usually equates to slow fishing regardless but should the water temperture suddenly drop, such as late afternoon when the sun settles behind yonder hill, the fishing is almost certain to shut down, like slow-mo to non-existent in a flash.
Water temperatures generally trend the same as air temperatures only slower; one notable exeception being the warm sunny afternoon in spring when the snow suddenly starts melting infusing said river with many gallons ice water...not so hot.
Cold water and low temperture downward trends do not affect trout health wise. Though prolonged cold snaps plummet water temperatures to near freezing, metabolisms all but shut and some might lose an ounce or two not eating. The flip side is another story. Prolonged high water temperatures (81 degrees is deadly) can be fatal, especially so if we anglers add to what is already a really stressful situation.
As water temperatures trend above 70 degrees the effect on trout metabolisms is similar to sudden downward trends and extreme low water temperatures. Trout stop eating, activity slows to a crawl and if trend continues for more than a day or so migration to cooler water is imminent. Cooler more oxygenated water is ideal but just getting to cooler water is paramount to survival--spring holes, colder tribs even the bottom of deep mostly shady pools. Unless trout have become somehow acclimated to high water temperatures (like the Firehole) little, if any feeding or activity, for that matter, occurs in 70 degree water.
The best thing for us is to leave them alone, hope for a change in the weather. Montana's so-called hoot owl mandate is designed for just that reason...to get us the hell off the water until conditions improve.