The Dry Fly Corner

If they ain’t rising they ain’t there: Blue Wing Olives (BWOs) - Mayfly

With the opening of the trout season in Wisconsin and Minnesota early season hatches include blue wing olives (size #18/#22) and midges (size 20 thru 40). Typically rising fish for BWO can be found in riffle pool configurations during the nicest time of the day (temperature wise). In the Spring this would be sometime between 11 a.m. and 3 p.m. The olives favor
overcast, misty, rainy weather so these conditions do not encourage a crowd.
Good hatches can last several hours or may sporadically go on for three hours.

Typically those fisherman who are just learning to fish olives carry an assortment of standard dry flies: Adams, catskill-type flies such as BWOs (of course), blue duns, thorax, or perhaps some Wulffs in appropriate sizes.
For example, if the hatch goes from 1 p.m. to 3 p.m. the new dry fly angler sees some rising fish after lunch and notices a few small mayflies in the air. Quickly one of the “standard” patterns is tied on. After 15 minutes no strikes. The frequency of rises per fish and the numbers of rising fish starts to increase. On goes fly #2 but only a false rise after another 20 minutes.

Fly #3 is attached with one missed strike, but now fish seem to be rising all over the place. “Where the hell did they all come from?” I think, as panic starts to set in. I should have practiced my casting. Maybe a smaller, longer tippet would entice a take.

While these easily could be the answers, let’s say these common problems are not the culprits.

It’s now 2:30 p.m. fly #5 is attached and finally I get a take. I knew fly #5 should have been put on first. At least it solved the puzzle, and we’ll be ready tomorrow. Tomorrow comes and fly #5 is put on first but nothing. It’s 2:30 p.m. and fly #1 from yesterday catches three in the last half hour. These damn fish want something different everyday, making it impossible and a pure guessing game. Very good for the seller of flies.

The BWO hatch presents its own set of unique problems. This may fly drifts under the surface or surface film for extended periods. The fish are rising to drifting NYMPHS or surface film emerging nymph/dun Bwo. What does this mean in plain English. The first five flies were high riding (on the surface) dry flies – not at the level in the water where the food is during the first 1 - 1 ½ hour of the hatch. (Since this article regards surface fishing only, nymphs and 1 to 3 foot droppers are excluded.)

For BWO early in the rising cycle (1 p.m. - 2:15 p.m.) flush surface film flies (low rider) are an absolute necessity. Such flies as CDC floating nymph/emerger, Barr dry emerges, RS-2 original, dub ball or foam emerger were specifically designed for this phase of the BWO surface emergence i.e. most of the food is in the bottom side of the surface film. Yes, these flies are much more difficult to see than high-riding Wulffs, but this implies medicore casting ability or below-normal eyesight.

In future articles we can address casting solutions. If you can’t use this film style fly, practice your casting during the first 1½ hours of the hatch or sit on the bank practicing your knots until the 2:30 p.m. - 3:00 p.m. classic dry fly hatch begins.

Do all mayflies emerge in this fashion? Absolutely not. Why do classic dry flies (hackled/stiff tails, i.e. sits high on the surface) work best in the last quarter of the BWO hatch? By definition, at the end of the BWO emergence there are few drifting nymphs or nymph dun emergers in the surface film as they have hatched and are floating on the water as duns (high riders) or cripples or flown into the bushes. Trout sight feed at the water level where most of the food is. Gee, aren’t they smart? Don’t
use high riding dry flies early in a BWO hatch because most of the food is elsewhere. Witnessing surface swirls is not necessarily indicative of trout talking duns/adults. (For a comprehensive explanation of rise forms, see In the Ring of a Rise by Vincent Marinero.) As the hatch ends, a number of different high-riding dry flies will work probably all of the original 5 in the matching size.

Where do currently popular patterns such as comparaduns and parachutes fit into the mix? On the clock cycle: before classic dries but after surface emerges. In particular, extremely selective trout seen to prefer pure emergers. Yet the comparaduns/parachutes are a good compromise because of their visibility. Comparadun/sparkle duns tied with bleached hair
can stand out like a beacon on the water and don’t seen to scare off most trout. Parachutes with typically white post (black for flat light) are a favorable compromise for those objecting with “I can’t see my fly.” Pattern such as the no-hackle sidewinder, invisible fly/Datus Proper, several CDC dun style no hackles are effective but present their own unique fly care problems.

Does the local BWO have a fishable spinner fall? No, this subspecies of baetis evidently crawl back into the water to lay eggs, we have never seen a real spinner fall.

Do we need two boxes of flies for this hatch? It’s more important to get several patterns for each level in the water column, a few varieties fo surface emergers/pure dries/ comparduns – parachutes for a total of 18 -24 will solve 90 % of the puzzle and not break the bank. For fly typers (depending on reader interest/ future comments will discuss exact features of these patterns.

Matching size for local BWO #18/#22 is critical, per the following age-old phrase size/shape/color. With the precise observations of Swisher and Richards in Selective Trout, where the fly sits in the water columns (high vs low flush surface) is an equally critical variable.
If the casting challenges and fly selections appear overwhelming, one can use a Sawyer pheasant tail nymph with an indicator and do well. The Day Fly Corner hope to go beyond merely catching.

Through some will disagree understanding basic entomology and what fly patterns coincide with a specific stage of emergence is required for successful matching the hatch dry fly action for the BWO.