The Ultimate Thompson-Nicola Hatch Guide

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The Ultimate Thompson-Nicola Hatch Guide
- Mayflies -
By Karl Bruhn

Order: Ephemeroptera
Family: Baetidae

Indentifying Features
Nymphs: Distinguishing features include three fringed tails of equal length, long antennae and large abdominal gills. Color: pale green or mottled olive, also light to dark gray. They are capable of rapid movement marked by quick flips of the tail propelling them forward in 15-cm bursts. Active through the year, they are most available to fish during their emergence swim.

Adults: There are two stages: the dun and the sexually mature spinner. Duns are duller in color than the glossy spinners which emerge once the duns have shed their outer skin. Wings of both are held upright on the water and are often likened to small sailboats.

Turkey Callibaetis Contributed by Phil Rowley
Courtesy of Flyfishing British Columbia
Masters Series Book 1

What to Look For
Large mating swarms of spinners congregate between midmorning and late afternoon either over the water or over open areas nearby. Bird activity provides good clues. Female spinners return to the water, dipping the tips of their abdomens to the water to release their eggs, normally without coming to rest. Bulging rise forms during emergence of duns on the surface indicate trout are feeding on nymphs just subsurface. Splashy rises indicate fish are feeding on adults.

Life Cycle
The cycle itself is simple; it is the fishing which becomes complex. Nymphs prefer the shallow near-shore zones and are rarely found deeper than about six metres. Dense mats of aquatic vegetation are the preferred habitat. They become most active prior to emergence, often swimming far from cover and thus become available to fish some time before emergence. Final emergence swim is rapid and transformation to duns is also quick, often occurring between midmorning and early afternoon. Transformation from dun to spinner is accomplished in about 10 hours. Males die a few days after mating; females die after egg- laying and will be seen on the water with outstretched wings.

When to Fish
Mayfly nymph imitations are a good bet any time for probing water in the absence of surface activity, but are most effective during late May to mid- June when the strongest hatches occur. Depending on altitude, this may last through July, but the most prolific hatches are normally over by mid-July. Fish adults any time mayflies are spotted on the water.

How to Fish
Parachute-hackled dry flies are the accepted way to go, but many fish, and especially large, older fish, concentrate on the emerging nymphs for long periods both before and during the emergence. Fishing duns on the dry line is straightforward except for the intricacies of matching the naturals as closely as possible. Emerging nymphs are best fished on dry lines with long leaders or slow-sinking lines; retrieve is from near bottom up towards the surface in quite rapid hand-twists or jerky pulls of about 15 cm followed by short pauses. Nymph imitations fished on a dry line just subsurface, twitched very slowly or dead-drifted,
can be good at times.

Spent Mayfly
Spent Mayfly Contributed by David Cooper
Courtesy of Flyfishing British Columbia
Masters Series Book 1

Fishing Tip
A keen eye is required to keep apace of hatch developments. The odd mayfly popping to the surface with no sign of fish activity often means the fish are concentrating on the nymphs as they begin their surface-swim off the bottom. Go deep. As the hatch builds, fish will follow to the surface; use the bottom to top retrieve.

Splashy rises call for the dry line and adult imitations and the most exciting fishing. Trout response to spent spinners is lazy; watch for sipping-type rises.

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The Ultimate Thompson-Nicola Hatch Guide