There are times on some of these tailwaters, most often during the summer, when trout feed on "normal" fare like caddis, mayflies, and sometimes even large terrestrials. But in most of these fertile, dam-released rivers, the vast majority of the aquatic insect population is made up of "midges"--tiny two-winged flies of the order Diptera, of which there are more than 100 species in North America.

Trout feast on these midges all year long, and in the late fall, winter, and early spring, they feed on them almost exclusively. These circumstances require special tactics and tiny flies that imitate the prevalent midge population. I consider these tailwater midge hatches to be one of fly-fishing's highest plateaus: To sight-fish to enormous trout with tiny flies and gossamer tippets is a true test of your angling mettle.

Midge Patterns
To be a proficient midge fisherman, you need a range of fly patterns that imitate every stage trout prey upon. You need to know what fly to use, and when to use it. Things can change suddenly during a midge hatch, or combined midge hatches, especially on productive water where large trout have the luxury of targeting specific stages of specific insects. Sometimes you'll tear up the river on a #20 red larva imitation, and then suddenly the fish switch to dark brown #24 pupa. If you can't recognize and make the change, the fish will get the better of you.

Yong Blood

Midge larvae. Even the best anglers sometimes overlook the importance of midge larvae. Midge larvae are long and slender with a uniform profile. The best imitations are nothing more than thread--twisted to create a segmented look--wrapped on a curved hook. Andy Kim's Yong Blood and Bear Goode's Sparkle Larva are the best examples of these types of patterns. Anything with a bead or with a pronounced thorax has the wrong profile. Take a seine or net with you and match your pattern to the specimens in the stream.

Yong Special

Midge pupae. Think long and slender for midge larvae, short and squat for midge pupae. The pupa's thick thorax contains the adult's developing wings. My favorite pupa imitation is Andy Kim's Yong Special, because it's the closest replication of the originals I see most often on the San Juan, Green, Frying Pan, and other rivers. Old classics such as the Black Beauty, Miracle Nymph, or Brassie work as well. On the Colorado River at Lees Ferry, the Beadhead Zebra Midge is the ticket, especially out in deeper water.

Johnny Flash

Emerging pupae. When midges begin to emerge, their budding wings become prominent, and they sometimes carry gas bubbles that trigger trout to feed. This phase of the transformation has been studied extensively by some very good anglers who have developed deadly imitations. Rim Chung's RS2 pattern was developed for finicky South Platte trout and has been widely adapted on the San Juan and elsewhere. The WD-40 is an emerging-midge pattern developed by John Engler on the Frying Pan, but it works almost anywhere there are midges. Johnny Gomez's Johnny Flash has the profile of the WD-40 and the emerging wing of the RS2.

Tak's Biot-wing Adult Midge

Single adult. As with all midge fishing, fly size is the critical element, followed by the shape and color--in that order. There are many excellent patterns out there to choose from. I have had good success with just a thread-body fly with two turns of grizzly hackle. That's all I can tie in a #24 or smaller. My friend Rick Takahashi ties a fly biot midge that is simply sinister to trout, and I swipe as many as I can out of his fly box when he is not looking.