Know your nymphs

“Nymphin’ NORM” has nothing against dry flies. If there’s a mayfly hatch on, he’ll float a dry. But, says the West Hills angler, “when I want to catch fish, I go nymphing.”

Norm Strieck acquired his nickname from buddies in the Sierra Pacific Fly Fishers, a club based in the San Fernando Valley, because “I catch a lot of fish on nymphs.”

Nymphing requires knowing a bit about a bug’s life cycle. The main aquatic insects in a trout’s diet -- caddis flies, mayflies, midges and stoneflies -- spend most of their lives underwater as wingless nymphs. All metamorphose into winged adults. Mayflies and stoneflies emerge directly from nymph to adult, and caddis and midges add an extra step, spending time as pupae before emerging.

Nymphing involves using ties that imitate bugs at these various stages, determining which type are in the water and figuring out when and where fish are feeding on them.

One of Strieck’s biggest catches using nymphs was a 22-inch brown trout out of the East Walker River north of Bridgeport, Calif., on a size 14 tungsten bead Soft Hackle Pheasant Tail that he tied himself.

Some purists use nothing but dry flies, which require accurate casting so the bug lands just so on the surface. The purists would just as soon put a hunk of stink bait on a treble hook as fish a sub-surface nymph.

Others equate nymphing’s “heave it and leave” technique -- using an indicator and waiting for a fish to strike -- with bait-fishing a worm and bobber, says Kevin Peterson, co-owner of the Troutfitter in Mammoth Lakes.

But facts are facts. Trout spend 70% to 80% of their time feeding below the surface.

Except during a hatch, when trout can easily be seen at the surface in a feeding frenzy, it’s not always obvious that trout are feasting on nymphs.

Before hitting the water, turn over some rocks to determine what’s there, advises John Stevenson, Sierra Pacific’s fly-fishing school director. If you catch a fish that you plan to eat, examine which bugs are in its stomach. Then match what’s under the rock or in the fish’s stomach with a nymph in your fly box.

Imitation nymphs aren’t the prettiest things in your collection. The Hare’s Ear, which imitates everything from a burrowing mayfly nymph to a pupal caddis, can’t hold a candle to an elegantly winged dry fly, such as the Royal Wulff, which doesn’t really resemble any insect.

But nymphs are probably the workhorses of a fly fisher’s arsenal. The website www.westfly.com lists 13 types of nymph that the Pheasant Tail imitates. In “Trout Foods and Their Imitations,” Tom Rosenbauer calls the Pheasant Tail “a near-perfect imitation” of the Baetis type of mayfly, an early-season favorite of trout and anglers in the Eastern Sierra.

Chris Jorgensen, a sales associate at the Orvis store in Pasadena, says he grumbles when the dries aren’t working and he’s forced to switch to a nymph. He has had “great luck” using tiny stonefly nymphs called Mercer’s Microstones on the West Fork of the San Gabriel River.

Imitation nymphs should be fished near the bottom of the stream, where energy-efficient trout hang out to escape faster surface currents.

Add weight to the tippet to get the nymph to sink -- or use a heavy bead-head nymph. Indicators should be continually adjusted to find the depth where fish are biting. Some even use a dry fly as an indicator. A popular summer tactic is a “hopper-dropper” combination: Using a buoyant dry fly, such as a grasshopper, on the surface and a nymph underwater doubles the chances of catching something.

Some anglers don’t like nymphing because the added weight or second fly makes it tougher to cast. Hooks get caught on bottom vegetation. It’s hard to spot a trout taking a nymph. Setting the hook can lead to tangles.

But anglers like Nymphin’ Norm think it’s worth it. In his 20 years of fly-fishing, Strieck estimates that 70% of the fish he’s caught have been on nymphs. And catching fish is what it’s about, he says. “Otherwise I might as well put the rod in the car and go home.”

To e-mail Julie Sheer or read her previous Outdoors Institute columns, go to latimes.com/juliesheer.