Within the Sierra Nevada, 90% of a trout's diet is from aquatic insects. As a flyfisherman, your goal is to entice a trout to select your fly as a food object. Once that selection is made, it's your problem as to how you're going to land that fish but that's for another topic. For now, your main concern is "how do I match the hatch"?
Hatches vary within the Sierra depending upon the geology of the area, the substrate of the stream, slope elevations, climate conditions, water conditions such as source and volume, and the vegetation of the area. That's a lot of criteria but we are talking insects, aquatic invertibrates, and they are pretty darn selective as to where they want to hang out.
Dave Hughes and Rick Hafele created a book called Western Hatches about 30 years ago. It is still the primary source of detailed information available. Dave and Rick make appearances at many flyfishing meetings and expos throughout the West. If you have the opportunity, be sure to meet them. They will often make a complicated subject much more simple to understand. They simplified "Matching the Hatch" to four steps: 1. Identify the insect, 2. Understand the habitat and habits of the insect, 3. Match the insect with your available fly patterns, and 4. Present that pattern with the proper behavior to entice the fish to take interest.
Hatch Charts: I have four hatch charts to reference. They will give a picture as to the insect, a description of it's habitat and habits, a suggestion of patterns, and a suggestion to the presentation of the fly. Sierra Tahoe, Eastside Sierra, Westside Sierra, and Southern Sierra.
Identify the Insect
You often can simplify the identification of the insect to 5 major categories. Rather than being concerned about a specific insect, be more concerned about the insect group. For instance, most caddis species hatch within a 4-6 week window but the caddis genera can hatch over a 8-10 month period. There are over 199 caddis species within the Sierra Nevada, 37 are endemic to the region.
- Mayflies - Nymphs: 2-3 tails, single claw at the end of each leg, gills on the abdominal segments.
Adults: 2-3 tails, wings held vertically, slender body
- Stoneflies - Nymphs: 2 tails, 2 claws at the end of each leg, gills absent from the abdominal segments.
Adults: 2 tails, long antennae, 4 wings that lay flat along the body.
- Dragonflies and Damsels - Nymphs: Large compound eyes, short antennae.
Adults: Large compound eyes, short antennae, no tails, 2 pairs of wings (Damsels wings together, Dragons wings outward)
- Caddis - Larvae: Minute antennae, No tails, gills in the abdomen, build cases
Pupae: Long antennae, No tails, wing pads, coccoon inside case
Adults: 4 well-developed wings, No tails, long antennae
- Midges - Larvae: No tails, minute antennae, no legs
Pupae: Head, thorax, and wing pads clumped, No tails, gills on top of thorax
Adults: No tails, Short antennae, only 1st pair of wings developed.
Understand the Habitat and Habits
Each group of insects prefer specific types of water and substrate. They will have certain movements at different times of the day or season. For instance, Stoneflies will often migrate to the shoreline during low light conditions while caddis will make an ascent for the surface in midstream. Overhanging trees, emerged boulders, and underwater logs within the stream will provide unique habitat for many insects.
- Mayflies - There are four categories of Mayflies, Swimmers, Crawlers, Clingers, and Burrowers. Eggs are laid at the water's surface and a sticky substance hold them to the substrate.Most remain within the stream for one year. The Swimmers are found in lakes, slow pools, rapids, and riffles. The Crawlers prefer streams, often protected areas with plenty of vegetation. The Clingers like to live in the fast water. They clings to rocks and vegetation as they are poor swimmers. Burrowers are found in lakes and streams needing a silty substrate that they can burrow 4-5 inches deep.
- Stoneflies - Need fast running water and cold temperatures, preferring the riffle sections of streams. The Sierra has plenty of these features within it's streams and the Stoneflies are probably the most prevalent choice when flyfishing.
- Dragonflies and Damsels - Found usually within lakes and ponds. Voracious predators, they crawl out of the water to emerge. As nymphs they inhabit the weedbeds. Dragons have a jet-propelled swimming motion. They occur in large numbers which makes them a great food source for fish. Damsels swim much slower with the use of 3 tail-like gill lamellae.
- Caddis - Caddis have a wide range of habitats. They will continue to hatch even if the stream temperatures become too warm for stones or mayflies. Many like to build cases or homes out of available material such as pine needles, gravel, sticks, and leaves. Some are free of cases and roam the bottom, often losing their hold on substrate and drifting. They go through a pupal stage where they make a cocoon within the gravel but emerge from the cocoon within 3 weeks to make a quick ascent for the surface.
- Midges - Chironomids will hatch year-round and cover a wide range of water conditions. You will find them in streams or lakes. Within Lakes, they prefer a silty bottom to burrow and will emerge when temperatures of 45-50 degrees occur. In the Spring, emergence will take place during the mid day, while most summer emergents are during the early morning hours.
Match the Insect
Fly patterns can be imitative, suggestive, or impressionistic. Sometimes, you need a very accurate representation of the insect. This can occur in very clear water when the trout are particularly spooky. Other times, a suggestive pattern is all you need, as in fast runs and riffles when the trout has to make an implusive decision. Take a look at the coloration and size of the insect, these can change between species. Getting the proper coloration and size is as important as the selection of your pattern.
- Mayflies - Swimmers include Gray Drakes (nymphs: A.P. Muskrat Nymph, Grey Timberline Emerger , adults: Gray Wulff, Gray Thorax Dun), Isonychia (nymphs: Zug Bug, Prince Nymph adults: Gray Wulff, Purple Haze), Baetis (nymphs: Pheasant Tail Nymph, RS2 BWO, adults: BWO Sparkle Dun, Blue Wing Olive) , Callibaetis (nymphs: Poxyback Nymph Callibaetis, Pheasant Tail Nymph adults: Callibaetis Bivisible Dun, Callibaetis Quilled Spinner) ; Crawlers include Pale Morning Duns (nymphs: Burk's Hunchback infrequens, PMD Halfback emerger, adults: PMD Parachute Dun, PMD Quiggly Cripple), Green Drakes (nymphs: Green Drake Poxyback Nymph, Gold-Ribbed Hare's Ear, adults: Green Drake Parachute Dun, Yellow Humpy), and Tricos (adults: Trico Spinner, Trico Quilled Parachute) ; Clingers include Little Yellow Mays (nymphs: Pheasant Tail Soft Hackle, Gray Hackle Yellow, adults: Bivisible Dun, Yellow Humpy), Pale Evening Duns (nymphs: Gold Ribbed Hare's Ear, Pheasant Tail Nymph, adults: PMD Hackle Stacker, Light Cahill), and March Browns (nymphs: Pheasant Tail Soft Hackle, Gray Hackle Peacock adults: March Brown Comparadun, March Brown Parachute Dun) ; Burrowers include Big Yellow Mays (nymphs: Burk's Hexagenia Nymph, Milt's Hexagenia Nymph, adults: Hexagenia Spinner, Watter's Foam Hex).
- Stoneflies - Skwala Stones (nymphs: Brook's Yellow Stone, Twenty Incher, adults: Yellow Stimulator, Yellow Madam X), Little Yellow Stones (nymphs: Little Yellow Stones , adults: Yellow Humpy, Clark's Little Yellow Stonefly), Golden Stones (nymphs: Golden Kaufmann Stone, Brooks Golden Stone, adults: Gold Stimulator, Rogue Foam Stone ), Giant Salmonfly (nymphs: Brown Kaufmann Stone, Bird's Stonefly Nymph, adults: Improved Sofa Pillow, Giant Rogue Foam Stone)
- Dragon and Damselflies - Dragonfly Nymphs (WoolyWorm, Carey Special ) Damselfly Nymphs: (Marabou Damsel, Sierra Damsel, Wiggle Tail) Damselfly adults: (Burk's Damselfly, Stalcup's Damselfly)
- Caddis - Green Rockworm (nymphs: Emergent Sparkle Pupa, Bird's Nest, adults: Kings River Caddis , Z wing Caddis), Spotted Sedge (nymphs: Anderson's Bird of Prey Olive, Fox Poopah Olive, adults: Partridge Caddis Emerger, E/C Caddis), Green Sedge Caddis (nymphs: Olive Soft Hackle, Chamois Nymph , adults: Goddard Caddis, Z Wing Caddis), Grannom (nymphs: Hogan's Good n Plenty Green, Peeking Caddis , adults: Missing Link Caddis, Olive Elk Hair Caddis), Saddle Casemaker (nymphs: Morrish Hot Wire Caddis, Caddis Emerger, adults: Olive Elk Hair Caddis, Hemingway Caddis, October Caddis (nymphs: Bill's Stick Caddis, Tangerine Dream, adults: Orange Stimulator, Orange Parachute Madam X)
- Midges - Chironomids (nymphs: Zebra Midge, Optimidge, adults: Martis Midge, Griffith's Gnat) , Mosquitos (adults: California Mosquito)
Presenting the Pattern
Now that you've identified the insect, chose the location of the stream or lake where that insect resides, and chose the proper fly pattern to represent the insect, all will fail if you do not present the pattern in a life-like manner. The presentations reflect the earlier choices of fly pattern, stream or lake locations, and the behavior of the insect. Putting these together, you will be able to select the best presentation for the hatch.
- Mayfly Swimmers: As Nymphs, these insects are active around weedbeds, brush, underwater logs, and open water. Their two tails form paddles that provide propulsion. It is important to show action with the presentation. On a stream, try a cast down and across allowing the current to provide the action. The pattern should not be weighted using a floating line with 8-12 foot leaders. Try to keep your casts short and accurate. On lakes, you need to use short strips or a slow hand twist. These patterns should be weighted and allowed to sink along the vegetation. Use a floating line in depths of 5 feet or less. Use an intermediate sinking line for greater depths. The Adults (Duns) prefer slower water and should be presented with a downstream slackline cast without drag. Spinner falls can be heavy and you should spot the fish first, casting the spinner pattern slightly upstream of the feeding fish.
Mayfly Crawlers: Nymphs do not swim well, preferring to slowly crawl upon the substrate. When dislodged, they make slow movements with their body until they can make contact with the bottom again. The crawlers have 3 tails. Present the pattern with a dead drift high stick approach. Since crawlers prefer faster water, weight the pattern or leader to get the pattern close to the bottom. The emergers will be close to the surface, so a presentation using an across and downstream as a dead drift works well. Adults (Duns) are best presented with an upstream cast providing an S turn to the line for a drag-free drift and presenting the pattern prior to the leader.
Mayfly Clingers: These insects are in the fast water, well-adapted to cling to the substrate. Occasionally, they are dislodged and tumble downstream until contact with the substrate is made. Use a High Stick Nymphing approach with the pattern or leader well weighted to get the pattern bouncing on the bottom. They emerge in open water so soft hackle patterns work well just under the surface film. Mend the line to minimize any drag. Try spotting the fish and cast just above them. Once the fly hits the surface, pull the line slightly to bring the fly underwater and let the current bring the fly to the spot of the fish. Adults (Duns) are on the fast water only shortly. The patterns need to be heavily hackled. Use a short upstream and across cast that will not cause drag and will allow the fly to reach the fish prior to the leader.
Mayfly Burrowers: In the Sierra, these are limited to the Hexagenia (Big Yellow Mays). Most of these will occur on lakes such as Lake Almanor but you will also encounter hatches within the upper Feather River where it's a slow meadow stream. As nymphs, provide a slow, upward sweep with the rod, then allow the nymph to settle back to the bottom and sweep again. Adults (Duns) need to be a drag-free float. Provide a slight twitching movement at times to imitate some struggling. During the dark evening, the spinners will fall and provide a drag-free float.
- Stoneflies: Most are poor swimmers and like to crawl among the rock and gravel of swift currents. When dislodged they drift with no movement until they touch substrate again. Many stoneflies become dislodged when they begin to migrate towards shore for emergence. Use a dead drift with little or no movement to the pattern. Cast up and across allowing a few feet of drift to get the pattern to the bottom. Tighten the line for a direct feel of the pattern and to minimize rolling. The adults need to be heavily hackled for floatation. Present the fly as a dead drift over rising fish. Skittering across the surface of a riffle section is also very effective.
- Dragonflies and Damsels: Dragonflies are strong swimmers so short strips will mimic the action of the nymphs. Use a floating line with long leader when fishing weedbed and shallow areas of less than 6 feet. Within deeper water, use a clear intermediate line. The fish will generally make hard hits as the actual nymphs have a great ability to elude. You may want to adjust to a stronger tippet. Damselflies are much slower in the water than Dragons. They swim with a clumsy movement that wiggles yet makes little forward progress. Use a slow hand twist retrieve. They also have a habit of diving when chased so most of the nymph patterns use bead chain eyes to provide weight to the head section of the pattern, achieving a diving characteristic. The marabou tail and flowing materials within the patterns provide subtle movement with the slow retrieve.
- Caddis: Presentation should be a dead-drift with an upstream or up and across cast. Allow the larvae patterns to sink to the bottom. The pupae are best fished in an ascending manner. Soft hackled flies will often be the a good choice at the end of a dead drift. On other pupa patterns, use a Leisenring Lift technique at the end of the drift. Adults demand a drag-free presentation. Some, like the Spotted Sedge, prefer to dance around overhanging brush and trees. So a skittering technique can be effective during windy conditions.
- Midges: Within streams, midge patterns are often droppers below another nymph pattern. It is fished as a dead drift with an upstream of up and across cast. Keep the rig close to the bottom. Hits will be strong and determined. Within lakes, the midges are spaced about 6 inches apart. Larvae and pupae patterns are fished close to the bottom. Attach your hemostats to the bottom fly and let the rig hit the bottom. Mark your line about 6 inches below the surface, this is where you will place a floating indicator. Remove the hemostats and the positioned indicator should keep your rig about 6 inches from the bottom. Fish the emerger patterns at higher depths. Use a little slow hand twist retrieve. Takes will be subtle and you will often need to focus on the indicator to detect hits. The trout will often suck the pattern into it's mouth and exhale it back out if it detects a foreign object. You will need to react with a strong upward hook set.