Throughout the Rocky Mountains this can be a killer tailwater fly. The freshwater gray shrimp is a classic trout fly that Western anglers have grown to love. This pattern is most effective when the shrimp are pumped into the river from the dam but anglers can catch fish with this fly throughout the year. Fisherman see the most success with the freshwater gray shrimp fishing it in a single or double nymph rig. Be sure to have a couple shrimp patterns next time you go fish the Rockies.