MOST NOVICE ANGLERS think that the only hard part of fly fishing is learning how to cast: once you've figured out the old “10 and 2,” the logic goes, the rest just falls into place. It's a comforting little myth — and it helps some people to justify buying a $700 fly rod — but things don't really work that easily in the real world. A good friend of mine, who has been a guide for many years, always draws a distinction between those clients who can cast and those who can actually fish . (He maintains that the former outnumber the latter by a wide margin.) Casting only helps you throw the line through the air. But the fish don't live in the air. They live in the water, and the water is usually moving.

To catch fish consistently with a fly rod, you've got to be able to control how your fly and your fly line are affected by a river's various currents. When you're fishing with a dry fly or a nymph, one of the keys to a good presentation is a “dead drift” — when the fly drifts naturally in the current, as if it weren't attached to anything. What makes this difficult is that the fly is, in fact, attached to the fly line, and if the line is drifting faster or slower than the fly, it will drag the fly through the water. This problem is called, aptly enough, “drag.”

Figure 2: Double Mend In this situation the angler is casting across an eddy (which will pull his line upstream) and fast water (which will push his line downstream). He will therefore have to make two mends. Always mend from far to near: First make the upstream mend, then the downstream mend. The key here is getting the line to hinge on the seams of the various currents. You can control the hinge point by how high you lift your rod tip and how much line you pick up off the water.

The way to combat drag is by “mending” your line; that is, counteracting the effects of drag-causing currents by moving the line after it's on the water. Mending is one of the least-understood aspects of fly fishing: many anglers are aware that mending is important, but they don't really understand why . Mastering the mend requires good technique, as well as an understanding of river hydraulics and how they affect your line.

The next time you look at the surface of a river, notice that the current is not uniform from bank to bank; different parts of the river move faster or slower than others. Problems arise for fly fishermen when they have to cast across currents of different speeds. For instance, the current near the bank is usually slower than that in the middle of the river, so if you want to cast to the opposite bank from where you're standing, your line will lie across the faster current, while your fly sits in the slower current. Because the fast current will take your fly line downstream ahead of the fly, the line will drag the fly behind it, creating a wake and ruining the dead drift. However, if you can arrange it so the line starts upstream of the fly, the fly will float naturally for as long as it takes the fly line to catch up to and then pass the fly. This is where the basic upstream mend comes in handy.

Figure 3: Reach Cast The reach cast allows you to throw a mend into your line before the fly hits the water. Cast directly across the river, and, just as the line straightens out, extend your arm and the rod tip upstream (or downstream, as the case may be). This will cause the line to fall diagonally across the current, which means that the fly has time to dead-drift before the line catches up. This technique works best in slower water and in deep pools where the differences in current are not very great.

Mending Mechanics

To achieve a good upstream mend, you've got to throw a certain portion of your line upstream of your fly. (See figure 1.) But getting your line to move up and down the river is harder than it sounds; most beginners end up dragging their flies underwater during the mend. To avoid this, you must lift the part of the fly line that you want to mend off the water , leaving the unmended portion of the line on the water. There are five keys to a good mend:

1. Mend as soon as the fly touches down, before the line has time to bond to the water's surface. This will help you avoid dragging your fly under.

2. Begin the mend with your rod tip close to the surface of the water. If you have a bunch of slack hanging from your rod tip, all you'll end up moving is the slack, not the line on the water. You may have to make a couple of quick strips to pick up this slack before you mend.

3. The hinging point, where the mended line meets the unmended line, should occur at the seam between the different speed currents. If you don't mend enough line, the current will cause the line to drag the fly; if you mend too much line, you can accidentally pull your fly out of the trout's feeding lane.

4. Lift your rod tip high, even over your head, during the mend. This will allow you to pick up more line and to avoid dragging the line across the water.

5. Mend with authority. A half-hearted mend rarely moves enough line. You'll probably over-mend the first few times — accidentally throwing your fly upstream with the line — but with some practice, you'll learn just how much power is needed to move the line you want to move without disturbing the fly.

Figure 4: Drag Mend In some situations, poor mending technique can be an asset. When you're making long casts across a fast current or when the current is really cooking, it's hard to make a big upstream mend without disturbing the fly. The solution is to drag the fly on purpose. First, slather your fly with a lot of floatant. Then cast upstream and beyond where you want the fly to be (A). Make a big, ugly mend, which drags your fly into the lane you want to fish (B). If you really lift your rod high and throw your weight into the mend, the fly should not sink.

Other Situations

Unfortunately, the upstream mend is the only kind of mend that many fly fishermen ever learn, and they apply it to all situations. But different current conditions call for different kinds of mends. For instance, if the fly is moving faster than the line, you must mend downstream. In more complex situations, you may have to mend several times or mend different parts of the line in different directions. (See figure 2.) The important thing to remember is that you want your mends to do the opposite of what the current does to your fly line.

The easiest way to determine which mends you'll have to make is to not mend at all. Cast a couple of times and watch to see how the current affects the line. If the line races ahead of the fly, you know that you need to throw an upstream mend. If the line makes an “S” shape — with part of the line nearest you racing ahead and the part closer to the fly lagging behind — you know that you need to mend first downstream, then mend just half the line upstream.

Once you get used to this idea, you'll be able to read the water and figure out which mends are necessary before you cast. There are no set rules to how many mends, and in which direction, you can make during a single drift — as long as you don't drag the fly across the water. An understanding of why you need to mend and how mending helps you achieve a dead drift makes the practice of mending a lot easier.