April/May Stream Update


Water temperatures have optimized across the region, and trout have followed suit with daily relentless feeding activity. Since trout are cold – blooded animals, their metabolism and therefore their need for food is dictated by water temperature. April & May typically provide the first reliable and continual optimal water temperatures, and 2017 has been no exception.

Fly hatches have in some cases been a bit earlier than usual, particularly on the mountain streams. Daily average temperatures and overnight lows have fluctuated considerably, providing the conditions for emergences of a variety of insects. The dry fly fisher has enjoyed exciting “match the hatch” opportunities as well as vivacious interest from the trout in “searcher” or “attractor” surface patterns during non- hatch periods. Nymph fishing has provided a mainstay, particularly during the morning and on cooler days. Hatch activity always indicates strong nymphal activity; every adult dry fly on the water ultimately has hatched from an aquatic nymph. Effective nymphing strategies include fishing a nymph imitation of the prevalent insect before and after a hatch, and nymphs account for some of the largest trout during any given hatch.

March Brown spinner falls have provided a lot of surface action since late April, and should continue through mid May.

Blue Winged Olives continue. Daily hatching activity and sporadic spinner falls have occurred with regularity, on cool overcast days. Duns exhibit muted olive – colored bodies and smoky wings, while the spinners have rusty – colored bodies with clear wings.

Tan and olive caddis provide exciting dry fly action, especially on the larger limestone streams. Splashy rise forms often indicate caddis activity, as the adults leave the water seconds after emerging from the pupae. The trout understand this, and will place a high priority on capturing these insects before they leave the surface. Some caddis species return to the water during the molting process to drink, skimming the surface. When the typical drag – free drift doesn’t produce, try “skittering” an adult caddis imitation across the surface of the water to mimic these behaviors, and expect explosive surface strikes.


Great Speckled Olive hatches occur toward the end of May & we’ve already seen some spinners flying around. This is a true size 10 –12 mayfly, and brings many large trout to the surface to feed. Look for emergences toward dusk in flat water areas, particularly at the heads and tails of pools.

Sulphur hatches occur during the evening hours on warmer days, and last until dark. Spinner and dun activity often mix – as the hatch diminishes, adults return to the water to mate and ultimately die and fall to the water. Trout become selective as the hatch progresses over the month, and the use of emerger, stillborn and thorax style dry flies will become more effective.

Light Cahills emerge sporadically throughout the month, and with their cream-colored bodies are mistaken for Sulfurs. Trout often key in on emergers during this hatch, refusing adult imitations.


Terrestrial insects become important, especially toward the end of May and during migratory flights of flying ants. As soon as nectar becomes available to the ants (via flowering plants) expect trout to become conditioned to them.

When the trout become ultra-selective during hatch times, throw them a “candy bar”. That is, present them something entirely different than what they’re feeding on, but something they associate with food. The use of a terrestrial dry fly is an excellent strategy to exploit the trout’s conditioned response in this respect.

Recommended fly patterns:

March Brown #10
Blue Winged Olive Thorax #16-18
Rusty Spinner #16-18
Tan/Olive Elk Hair Caddis #16
Great Speckled Olive Parachute #10-12
Sulfur Thorax or Parachute #14-16
Black Beetle #14-16
Black or Cinnamon Ant #16-18
Dark Sulfur Nymph # 14
Hare’s Ear Nymph #16-18
Pheasant Tail Nymph #14-16
Hydropsyche Caddis Larva #16
Sparkle Caddis Emerger #14

Fish and stream photos courtesy of client and professional photographer Mark Sargent, after a wonderful day of guided fly fishing.