Fall is here and rivers are low, cool and clear, which is good news for fly anglers. But insect hatches are scarce, or the bugs hatching are so small many fly anglers don’t want to bother with them.

That’s no reason to put away the fly rod. It just means it’s time to start nymphing. Not only does it work year round, it’s also a way to increase your knowledge of how trout feed.

“It’s certainly a different way to fly fish,” said Eric Moncada, salesman at Anglers fly shop in Boise and president of the Boise Valley Fly Fisherman. “It’s an art in its own.”

As much fun as it is to see a trout snatch a fly off the surface, trout feed subsurface more than they feed on the surface.

That means they’re usually feeding on the early stages of a riverborne insect’s life, which nymphs imitate. They’re a staple of a trout’s diet.

“It gives you a better understanding of what’s going on underwater, and that’s what fly fishing is all about,” Moncada said.

THE BASICS

Start with a 9-foot leader with about a 2X to 4X tippet and tie on a heavy nymph with a beadhead or a large fly like a stonefly.

With tippet at least one size smaller than the leader, tie a clinch knot to the bend of the fly’s hook with about 12-to-16 inches of tippet. Tie the lighter tippet to a small, preferably unweighted nymph, such as a prince, pheasant tail or hare’s ear. The lighter tippet will break if the lower fly snags so you don’t lose both flies.

Depending on the speed and depth of the river, add weight about a foot above your flies. Remember the longer distance between the weight and your two flies, the more likely your flies are to trapeze and tangle with each other. Compact is better.

Now place your indicator at least 6 feet above your flies, and preferably higher. This is where the trade-offs begin.

You want your flies to sink quickly and drift naturally, which means heavier is better. Adding weight also creates drag and minimizes the slack in your leader between your flies and the indicator.

But too much weight will cause the flies to snag and/or drift unnaturally. Too little weight and the flies sink slowly and there’s often slack between your flies and the indicator, which make strikes harder to detect.

The farther up your leader the indicator is, the deeper water you can fish, but the more weight you need to eliminate the slack.

The right combination is a balancing act, and it might change every time you move to a different spot where the depth or the current’s speed changes.

ADJUST YOUR CAST

Remember it’s tricky to cast an indicator with two flies and weight. It’s clumsy and you will quickly miss the elegance of a dry fly. But stick with it. Let your backcast completely unfold and bring it back gradually. This isn’t the time for distance casting. Keep it short.

Also, frequently check your rig for tangles (like every 6 to 10 casts). Just give it a quick glance. If it’s tangled, you’re wasting your time. Also check your hooks for debris.

FINDING GOOD NYMPHING WATER

The key to nymph fishing is determining where fish are holding and how you can effectively get your flies in front of them.

Look for water that’s anywhere from shin deep to chest deep and flowing slow-to-moderate speeds. Current that’s walking speed is about right. Rocky or cobbled river beds and riffles are prime nymphing water.

THE BLANKET APPROACH

When you find likely water, concentrate on fishing short sections of river perfectly. Trout typically won’t travel far to take a nymph. They’re trying to maximize their food intake while minimizing the energy they must expend to get it.

Try breaking the river into 20-foot sections. Why 20? Because you probably have a 9-foot fly rod. If you hold your fly rod directly upstream, you can easily drop your fly in the water about 10 feet upstream. Now let it drift downstream and follow the indicator with your rod tip.

When it’s at the bottom of the drift, that’s another 10 feet downstream, or about 20 feet total.

By adding line you can add length to that drift, but don’t do it at the expense of controlling your flies and the indicator.

If you drift through an area numerous times and don’t get a strike, take a couple steps downstream or wade (or cast) out a little farther into the river and cover new water. Do it incrementally until you’ve thoroughly covered all the water around you.

Don’t get stuck in a rut of casting into the same water over and over. If you’re not getting strikes, it’s counterproductive.

LINE TENDING

This is a critical skill as you add distance to your cast. Cast upstream and keep your rod tip pointed toward the indicator, then pull in line while the indicator drifts toward you. As your indicator drifts by, feed the line back out.

Your fly line should be upstream of the indicator, or forming a slight “J” shape below it. Your line should never pull hard enough to drag the indicator downstream. Also, the less line you have on the water, the quicker you can set the hook.

If you see the indicator dive, twitch, pause, or do anything out of the ordinary, set the hook. Don’t jerk your rod; lift it, or flip your wrist upward. It usually doesn’t take much pressure to set the hook. If there’s no fish there, you don’t want to pull your fly completely out of the strike zone.

BE AN ACTIVE ANGLER

Casually flipping a nymph and indicator into the current and passively waiting for a strike won’t make you a successful nymph angler.

Switch your thinking from the horizontal plane of the surface to the three-dimensional world beneath it.

Think of where the fish are holding and consider the depth, structure, currents and cross currents surrounding it. Then figure out how to effectively get a fly in front of the fish. Work to perfect that process and not only will you catch more fish, nymphing will be a lot more interesting.

ADVANTAGES OF INDICATORS

They give you the luxury of being able to fish with a slack line and learn a drift.

For example, when you see your indicator go down and don’t hook a fish, try to perfectly duplicate the drift. If it goes down in the exact same spot, it’s likely a rock or submerged log.

The indicator doesn’t just let you see strikes, it tells you if your flies are getting to the bottom and at what speed they’re drifting. If your indicator is stuttering on the surface, it means your flies, or the weight, are dragging on the bottom.

Within a few casts, you get an idea of bottom contours.

NYMPH FISHING WITHOUT AN INDICATOR

The bottom of a river is rarely uniform in depth, and removing the indicator helps keep your flies near the bottom and in the strike zone.

The best place to ditch the indicator is where you can get close to prime water that is fairly shallow, such as thigh-deep or shallower.

You’ve lost the visual clues the indicator provides, but to overcome that, fish a short line — as little a few feet of fly line outside your rod tip.

Sink your flies into the strike zone and lead them through slightly faster than the speed of the current so you keep contact at all time.

If the “no drag” mantra is sounding alarms in your head, relax. You’re compromising between drifting as naturally as possible and detecting every strike.

Keep your rod parallel to the water surface and when you get to the end of your drift, lift the rod gradually. When the fly breaks the surface, flip it upstream and start the process over again.

It will surprise you how jolting a strike feels on a tight-lined nymph.

But there’s more ways to detect a strike than feeling it. Drift with a few inches of leader above the water and watch the butt section where the leader attaches to the fly line. It’s often got a little bend in it. When you see that bend start to straighten, set the hook.

Want to detect those really subtle strikes? This sounds crazy, but it works. Watch the beads of water hanging on the butt of your leader. When a fish hits, it knocks those beads of water off the line. It’s amazing how quickly you can detect a strike before you feel it.

After you get the feel of leading your flies through the drift, you can add a little more line and cover more water with each cast.

But the more line you have out, the harder it is to maintain contact with the flies, detect strikes and control your drift, so don’t overdo it.

ADAPT YOUR GAME

Nymph fishing is a skill, and you will improve with practice.

Use trial and error until you figure things out, then adapt your techniques accordingly. Expect to develop your own nymphing style. There are many effective ways to do it, and you can tailor them to specific rivers, or types of water you’re fishing.

MORE NYMPHING TIPS

• Be stealthy when you approach the water and pay attention to your shadow. Fish will feed close to shore if undisturbed. Here’s a good rule of thumb: Don’t wade into a spot unless you’ve already cast there.

• Use stout tippets. They don’t spook fish, and if you’re doing it right, you will frequently hang up on the bottom. One or two tippet sizes larger can mean the difference between getting your flies back and a time-consuming re-rig.

• After snagging on the bottom, double check your hooks. They can bend or become dull.

• Trout aren’t that selective about patterns. Unlike a hatch where they’re conditioned to eating one insect, many different kinds of larval insects may float by a fish during the day. Getting your flies in front of the fish is usually more important than what patterns you use.

• If your flies aren’t occasionally hitting the bottom during your drift, add weight, or move the indicator farther up the leader.

Roger Phillips: 377-6215, Twitter: @rogeroutdoors