Isonychia nymphs are active for most of the fishing season, which makes a nymph imitation a good searching pattern if you can’t tell what the fish are feeding on. These are predatory “swimmer” nymphs, which means that you don’t want to dead-drift them. Instead, use short strips to move the nymph from the middle of the current toward the bank. Trout will often chase down these speedy nymphs, which means that they don’t inspect the fly as much as they would a dead-drifting pattern, plus you don’t normally need to go with an ultralight tippet. Stripping or swinging this nymph through a run prior to an emergence can be very productive.
Here’s another great video tying lesson from Tim Flagler of Tightline Productions, who uses several neat tricks to create a weighted Iso nymph. I love the way he positions the materials on the hook so carefully to create a realistic silhouette, and his methods for controlling materials and tying them off neatly are useful in all your tying.
Hook: 3X-long nymph hook (e.g.Daiichi #270), size 12.
Bead: Black, 7/64-inch.
Weight: .020 lead-free wire, 15 wraps.
Thread: Dark Brown, 70-denier or 8/0.
Rib: Gold Ultra Wire, size Brassie.
Tail/abdomen: 5 dark-brown pheasant-tail fibers.
Wingcase: 8-10 dark-brown pheasant-tail fibers.
Thorax: Dark maroon rabbit and hare’s-ear dubbing, blended.
Adhesive: UV Clear Fly Finish, thick.
Note: Rough out the thorax to create legs.