This month's fly of the month is the leech. We often think of these as blood-sucking worms but they are found in most of the world and can be used effectively on windy days or as an attractor in muddier water.
Why Leeches – Leeches are aquatic worms that live in rivers, lakes, and streams all over the world. Whether you are fishing in winter or summer, in high or low water, it’s always leech season. Most leeches are ½ inch to 3 inches in length. They come in a wide array of colors, including black, brown, green, and red. They can be seen on their own—hanging off rocks or logs—or lounging on the bodies of fish.
Leeches are sensitive to light, so they’ll most likely be found in deeper waters during the day and in shallower areas at night. During brighter days, they retreat into hiding. They swim by undulating their bodies, elongating and contracting as they go. They're not fast swimmers so use a slow retrieve with a weighted fly head to imitate their action. These unbalanced patterns are animated regardless of the style and speed of retrieve, which is why bead and conehead woolly bugger and leech imitations tend to be particularly effective.
When threatened, leeches will curl up in a tiny ball. Anglers often refer to this behavior as a "short strike," as trout will smack the leech to make it curl. If you expect this behavior and hold the retrieve long enough for your pattern to fall deeper into the water and fold, you will turn short strikes into takes.
Often you will see leeches use a stream’s current to travel from place to place. You can find them under rocks and logs, or on top of submerged branches where they will drift with the current. Because of this behavior, you can use a dead drifted pattern that will allow you to use them without actively fishing.
In still water, fish the leech near or at the bottom of the water. In duller conditions, your fly should be presented in the muddy bottoms of shallows, banks, and drop-offs. In freestones and tailwaters, leech patterns can be fished with a retrieve like a streamer with varying speeds or dead drifted like a nymph.
In deeper waters try using the sinking method, where you cast your line along drop-offs and let it settle to the bottom or near the bottom of the water. Slowly bring the fly back using short and slow retrieves so that the leech’s swimming is imitated along the bottom.
In the shallower water try the floating line method and use a floating line that has a long tippet or leader. A quick presentation requires using a weighted fly, sinking tippet, or sinking dressing. Go for tippets from 3x to 6x making sure there’s enough to reach the bottom and wait for the fly to settle at the bottom or near the bottom and then use slow pulls to retrieve, pausing every few seconds. When there are low light conditions, double your retrieve speed and keep your fly along the muddy bottoms or weed bed.