Anglers who desire to throw streamer flies can leave the large meat box in the closet. Right now is the prime time for small streamers. There is a predominance of little fish in the river now coming from this year’s spawning cycle. Anglers willing to do the math can build a strong argument for fishing small streamer flies now.
Colorado Parks and Wildlife (CPW) places closures for spring spawning activity on specific waters from March 15- May 15. Given those dates anglers can do the math. Small variables like water temperature can lengthen the gestation period before eggs hatch into alevin. But it is roughly a sixty-day period from when the eggs are laid ’til they hatch.
Alevin are the first stage in rainbow trout development where the egg sac is still attached to the underbelly of the fry. Once the egg sac has been absorbed the small trout is in the fry stage. Near an inch in length, fry will swim around the bed. High water will begin to move them as they develop.
Considered fry until three inches or longer, the little fish will start to grow parr markings. Parr markings are the characteristic patches that color small rainbow trout. During development, the parr marks are lost as they mature into fingerlings.
The period from a newly hatched rainbow trout or alevin to fingerling is the window we find ourselves in currently. There really are not nearly as many fingerlings or year-old trout as there are fry. Fry are learning to swim and swift currents take the little parr marked minnows for an uncontrollable ride. The high numbers of little trout entering the food chain is a pseudo-hatch so to speak.
Swift swimming brown trout make easy meals out of the highly targetable and extremely visible morsels struggling in tumultuous currents. Competing against a full grown, snaggle toothed, monster brown trout is a losing game for baby rainbows.
So the window is open for the new round of rainbows to run the gauntlet into summertime. Anglers wanting to throw streamers should be converting their knowledge of rainbow trout development into intelligent choices for fly selection.
The small rainbows range from 1”-3”. Their sides have very visible patches down the length of the fish. They do not swim very well and therefore appear struggling. Present your flies to mimic struggling for a realistic presentation.
Gary Lafontaine was a great fly angler, teacher and person. His writing and videos taught worlds of anglers and imparted a thirst for fly fishing I haven’t quenched in over thirty years of fly angling. He believed a struggling, weak, injured baitfish could not swim with strength. So he would deliberately cast toward the shore when float fishing and mend downstream. The downstream mend would pull the streamer with the current the way a wounded or easy meal baitfish would swim.
It’s always a good idea to try a different retrieve when throwing streamers. This presentation can be a killer with the dropping flows still keeping water in the kinda high category but definitely heading down. Trout have seen a lot of the small fry blown into the river. Ambush points, rocky obstructions and woody debris all create the opportunistic strike positions predators seek out.
Fish the little streamer flies on a short leader. Little flies need not a lot of weight to sink them but a sinking head line will pull the fly down with a seductive drop. The depth changes a few feet off the bank is good water to fish.
Targeting obstructions with a light-colored, but striped to imitate parr marks, streamer can bring on some healthy adversaries. Brown trout are ready to feed and the little rainbow fry are just the big bite of protein they are used to seeing in the river.
Now is not the time for your bushy, articulated streamers. A small, white fly with a glue gun egg sac is a unique streamer to use for this time of year. But any little streamer that swims eagerly can mimic the first few stages of rainbow trout development. Break out the small ones you’ll be glad you did.
Michael Salomone moved to the Eagle River valley in 1992. He began guiding fly-fishing professionally in 2002. His freelance writing has been published in magazines and websites including, Southwest Fly Fishing, Fly Rod & Reel, Eastern Fly Fishing, On the Fly, FlyLords, the Pointing Dog Journal, Upland Almanac, the Echo website, Vail Valley Anglers and more. He lives on the bank of the Eagle River with his wife, Lori; two daughters, Emily and Ella; and a brace of yellow Labrador retrievers.