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Mayflies Caddisflies Spring 2015

Apr 16, 2015 | Mike Lawson

April reminds me a little bit of October. There are so many great spots to fish you want to be everywhere at once. That’s like October. What’s different is that in October most of the good hatches of mayflies and other aquatic insects are winding down while in April everything is winding back up. It’s worth looking at these important aquatic insects for anglers lucky enough to fish the waters of Henry’s Fork Country April and May.

Tyler Treece with a fine brown caught by Robert Deford on Tyler's first guide trip of the year

Blue Winged Olive
I always look forward with great anticipation to the first mayflies of the year, commonly called Blue Winged Olives or Baetis. There are a number of other mayfly species that fall into the Blue Winged Olive category so I like to use the scientific nomenclature when discussing these very important insects. Baetis are quite easy to identify. Most range from hook size 16 down to 22 but some are even smaller. All of them have two tails and a miniscule secondary or hind wing. Body color ranges from pale gray to tan with an olive cast. There are several important Baetis species and related mayflies common to the Henry’s Fork and other western waters but the one that gets most of the play is Baetis tricaudatus. I tie most of my patterns on size 18 but the naturals can be a size larger or smaller.

A female Baetis - 2 tails - minute secondary wing (photo Jim Schollmeyer)

There are some interesting characteristics of this mayfly. They are multi-brood with a major emergence in March and April and again later in the fall. The spring brood is a littler larger than the fall. After mating it is also important to know that the egg-laying stage or spinner does not do the picturesque romantic dance in the twilight. Instead they crawl down into the water from rocks, branches or other bank structure to lay their eggs.

The best hatches occur on cool, cloudy days. In fact the rottenest weather often brings forth the best hatches. One thing I like about the spring Baetis is that it stretches over a 4 or 5 week period. On warm days look for them in the late morning. Colder days will bring them out later in the day. Most of the local rivers have good Baetis activity. As a result of colder spring water temperatures the trout don’t like to hold in the fast water to feed on the surface. Best dry fly fishing occurs on the slower stretches of water. My favorite areas of the Henry’s Fork are Last Chance along with the slower sections of the lower river. They also come off on the Teton and South Fork of the Snake. Nymphs can be very productive in fast water. My favorite is a size 16 Pheasant Tail tied slender or Brown Two Bit Hooker. I hate fat nymphs. When the bugs are emerging you can use a Baetis Half Back Emerger, Baetis Sparkle Dun, Olive Parachute or Baetis Nohackle.

Mark Rockefeller and Chris Lawson this spring on the Teton River

Western March Brown
Later in April you’ll start seeing larger mayflies mixed in with Baetis and caddisflies. This mayfly is commonly known as the Western March Brown, sometimes referred to as the Black Quill. It belongs to the genus Rhrithrogena, members of the clinger nymph group of the family Heptagenidae. While the nymphs prefer faster currents with rocky bottom structure they can also be found in the slower sections of the rivers with cobble or gravel bottom.  The duns have two tails, a large secondary wing, with dark mottled primary wings. Seeing these large mayflies on the water can be exciting but the trout often don’t get too enthusiastic over them. One reason for that is the emerging duns usually break free from the nymphal shuck on or near the bottom. With the emergers readily available in the water column it is likely the trout are feeding on them without the knowledge of the angler.

Western March Brown - 2 Tails - Mottled Primary Wing

The March Brown’s emergence spans almost a two month period on the Henry’s Fork. They are common on the lower Henry’s Fork in late April and early May. On the upper river at Last Chance they don’t normally show up until later and are usually going strong over the Memorial Day Weekend into early June.

I like size 12 and 14 patterns. Dark frazzled nymphs like the Gold Ribbed Hare’s Ear work great when fished deep in the currents. In my experience the most effective patterns are emergers and soft hackles. The fly should have a dark tan or brown/olive body. You can swing soft hackles in the currents or use a soft hackle as a dropper from a dry fly. Another good option is to use a double dropper nymph rig with a dark bead head nymph and a soft hackle fished dead drift. If you find fish feeding on the duns they normally aren’t very selective. A standard size 14 Dark Quill Gordon will work as well as a Parachute Adams or Brown Sparkle Dun.

Mother's Day Caddis - Green Body - Dark Gray Wing

I rank these green bodied caddisflies near the top when it comes to early season dry fly fishing. These dark caddisflies belong to the genus Brachycentrus and are best imitated with size 14 or 16 flies. Commonly known as the Mother’s Day Caddis they usually start emerging a few weeks before Mother’s Day sometime around the middle of April, depending on the year. In fact the water on many of the rivers is too high and off-color to fish these caddisflies by the Mother’s Day Holiday.

The best hatches of the Grannom occur on the lower stretches of the Henry’s Fork from the confluence with Warm River downstream to St. Anthony. Sometimes Fall River puts so much dirty water into the Henry’s Fork that it is unfishable below the Chester Dam. These caddisflies are also important on the Lower Teton River and the South Fork of the Snake.

These 2 Patterns are a Must when fishing the Grannom hatch

The Hemingway Caddis was originally tied to imitate the Mother’s Day Caddis. Named after Jack Hemingway who loved to drive over from his home near Sun Valley it has an olive body with medium to dark dun hackle. Another great pattern is the Olive E-Z Caddis. Along with these dry flies you’ll need some caddis emergers. You shouldn’t need anything more than an Olive Partridge Caddis Emerger. Drop the emerger about a foot below the dry fly and fish it dead drift. 75% of the trout will take the emerger.

It is very difficult to predict what fishing will be like over the next four or five weeks. As of this date the snowpack is well below normal at about 70%. Warm spring weather arrived early in March. Above normal temperatures started the runoff early knocking the much of the Lower Henry’s Fork out of action. Spring hit the skids in early April bringing cold, damp windy weather. It helped shut the runoff down and brought the fishing back to where we like it on the lower river. There have been good hatches of Baetis and the March Browns and Grannoms are starting to show. The weather forecast looks good for the next 10 days with near normal temperatures. We’d like to see a lot more precipitation but there isn’t much on the horizon. This could make for some great fishing with the Mother’s Day Caddis.