May 28, 2014 SF Boise River Dry Fly Fishing Report: 70°+ /Hard afternoon wind from all directions

Posted by Nate at 8:00 PM on Wednesday, May 28th, 2014

There are times when you dry fly fish that too much of a good thing becomes a problem. A good thing is bugs at the surface and fish up eating them. The good thing goes bad when there are so many bugs at the surface that the fish can't eat them all. Every fish in the system is so packed full of that bug that there is no room left in its stomach to eat. That's exactly the way the South Fork felt today. The caddis hatch was so profuse that there were thousands of bugs on the water all day long and in many sections of river, the fish paid no attention to them. I saw at least a dozen salmon flies that floated the surface for as far as the eye could see without a fish eating a single one of them. Yes, the SF is showing signs of the fish population being totally full; add to that, every fish we netted had a solidly full belly.

At some point in time in your dry fly life you'll have to deal with overfed fish; and I'm not sure there is a good solution, but here's a strategy for you. Recognize two things that you must overcome:

  1. Full fish rarely rise to your Searching Flies, so don't anticipate to catch a lot of fish blindly. Today the fish shied away from our go-to Searcher Fly, the Black Gold Stimulator, which has been catching fish like crazy since the opening of season. So if a fish won't eat a Searching Fly, you must cover a lot of river and find those pods of fish that are still indulging in the hatch party.
  2. You must dial in on what fly selection to use when you find feeding fish. Today caddis was the main player on the river, and there were zillions of adult bugs in the system. The caddis ranged in sizes from a micro Size 20 to a solid Size 16. Most of the body color of the caddis was dark baetis green. I strongly suggest you match the smallest caddis you see in the hatch and match it perfectly. If the surface of the water is slow moving and slick, drop a tippet size to serve the small caddis you've selected. I am suggesting that you must be perfect because the fish you are dealing with have more natural bugs than he can eat and he can be selective about which bug is on the menu. When fish are full, they won't target large bugs; they connoisseur small bugs. There is always room in the gullet of a fish for a micro caddis, but the larger size caddis could plug the system.

The other trick you can use over stuffed fish is serve another phase of the hatch. The predominant bug in the South Fork system is an adult caddis right now. Today I had pretty good success fishing our Green Tantalizer Size 18 because it imitates a hatching caddis. That different look will often trigger takes. It may seem like my hypothesis of overfed fish is a lot of hot air, but I have seen this strategy work so many times that I am a true believer. I've been asked many times, "What is your favorite salmon fly pattern?" and my answer to that is a Size 20 Emperor Caddis.

Given all that, the fishing on the SF Boise was tough today on the section of the river we visited. The fish showed every symptom of being overfed and we fell back to the strategies I just explained. I can't tell you we executed the system to perfection, but we put a couple dozen big rainbows in the net before the late afternoon wind blew us off the river. We will upload a video version of this blog within the next few days.

Flies that Caught Fish:

#18 Green Tantalizer
#20 Green Emperor Caddis
#20 Olive Brown Emperor Caddis
#4 Salmon Fly (hooked our fish on this pattern and lost in in the fight)
#12 Black Gold (only hooked one fish on this bug)
#16 Black Get Her Done Caddis

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