Crayfish flies are a little more versatile than you might think, and there are several ways to fish them—as long as you get them down deep. Most patterns are weighted, but in water deeper than a few feet, you usually need to add weight or use a sink-tip line (or a full-sinking line in lakes and ponds). As always when fishing deep, keep your leader short, between four and six feet. Otherwise, the fly will ride up and away from the bottom debris, ledges and rocks that make for prime crayfish habitat.
In rivers, fish craw flies the same way you’d fish deep streamers, by banging the banks or swinging them downstream. Crayfish aren’t powerful swimmers, and sometimes they get dislodged and swept downstream—just like a free-floating nymph or an injured baitfish—so a dead drift can also be surprisingly effective (even under a strike indicator). It’s also worth fishing tail-outs and back eddies, where bass, in particular, patrol for bigger meals.
In lakes and ponds, there’s no magic retrieve formula. Brisk pulls of four to 12 inches mimic a startled crayfish, and sometimes this will get a predator’s attention. But you can also use a slow retrieve with occasional small hops, like a crayfish going about its business, blithely unaware it’s in danger. Big fish often pin craws to the bottom with a blow intended to crush and disable them, so strikes are hard to miss. When fish hunt craws, they come ready to rumble—and you should, too.