Fly Fisherman Throwback: Fishing the Henry's Lake Damselfly Hatch

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This article originally appeared in the June 1976 issue of Fly Fisherman magazine. Click here for a PDF of the print version of "Fishing the Henry's Lake Damselfly Hatch."

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When the discussions of fly-fishing enthusiasts turn to great hatches, it is the likes of the Green Drakes and the Salmon Flies that are frequently mentioned, for those are among the traditional hatches that have compelled men for decades to travel great distances with great expectations. A lesser known yet exciting and perhaps more unusual hatch is the damselfly hatch of Henry's Lake in southeast Idaho.

During late June and early July, the availability to trout of damselfly nymphs in Henry's Lake is at its peak. When the phenomenon occurs, the trout become appropriately selective in their feeding habits, as with other major hatches. Obviously, presentation of a well-designed damselfly nymph with an appropriate retrieve during this period of selective feeding has the potential to yield outstanding fishing, the very sort of angling expected during these "high holidays" of the angler's season.

Although damselfies hatch in waters across the United States throughout the entire summer, the unique physical characteristics of Henry's Lake contribute directly to the intense period of peak activity that characterizes this hatch. The average depth of Henry's Lake is only twelve feet and the thick ice and snow covering it each winter can result in a heavy winter-kill of aquatic life in the shallow areas along the shoreline. The damselfly nymphs respond to this threat by migrating each fall into deeper water.

Then, in early summer as the water warms, a massive damselfly migration begins. Thousands of mature damselfly nymphs, totally exposed to the predatory trout, swim at various depths toward shore with a side-to-side motion. When they stop to rest periodically, they gradually sink, often in a downward spiral. Then they resume their slow swim toward shore where they crawl onto weeds, logs, or any other available object. After lying in the surface film, where their breathing apparatus under­ goes the change necessary to enable them to emerge from the water, they crawl out and slowly shed their nymphal shuck.

During this period the damselfly nymph might be referred to as an emerger, but it might be more appropriate to classify it simply as a "migrator," because it spends much more time migrating than actually emerging.

Among those damselfly-nymph imitations that have proved effective during this migration, one ot the finest has been created by Hal Janssen, an innovative West Coast fly fisherman with whom we fished Henry's Lake most re­ cently last summer. The materials employed by Hal for this pattern are as follows:

• HOOK: Mustad 9672 3XL (down-eye) # 8-12.
• TYING THREAD: Pre-waxed olive (Herb Howard).
• TAIL: Brownish-olive marabou (1/3 body length).
• ABDOMEN: 40% bleached beaver mixed with 50% olive rabbit and 10% fluorescent-orange rabbit.
• RIB: Tying thread.
• WING CASE: Mottled turkey wing.
• THORAX: Same material as abdomen, palmered with ginger hackle (clip top and bottom; trim sides short to imitate legs).

By combining the knowledge gleaned by Hal during his past trips to Henry's Lake with our observations that summer, we were able to determine that in presenting the damselfly pattern the single most important factor is the retrieve. Keep in mind that, while the damselfly nymph may not be a particularly efficient swimmer, its movements are methodical and repetitive. Thus with the Janssen damsel fly pattern, very short strips during a slow retrieve with regular pauses is particularly effective, each strip of the line being only an inch or so.

Occasionally modifying the retrieve in an erratic manner can provoke a strike. Perhaps this sudden unusual motion captures the trout's attention and momentarily separates the imitation from the multitude of naturals. Keep this technique of deliberate variation in mind when fishing the damselfly hatch and experiment in particular with variations in retrieve until you hit one that is a strike­provoking supplement to the normal methodical retrieve.

One final consideration that will frequently spell the difference between success or failure among anglers fishing the damselfly hatch is the position of the rod tip during the retrieve. Keep it at–or even below–the surface to avoid the sagging loop of fly line that inevitably hangs from a rod tip held above the surface during a slow retrieve. Only by this technique will the more delicate strikes be felt.

Fast-sinking and extra-fast-sinking lines are generally employed with nine-foot leaders tapered to 5x. Depths at which to begin the retrieve must be found by trial.

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