The Eddy Line

Get your (dry) fly on

Story and photos by Patrick Straub Explore Big Sky Fishing Columnist

April showers bring May flowers – but April also brings Blue Winged Olives, spring stoneflies, March Browns and Drakes, and the renowned Mother’s Day caddis hatches. For me, April means the skis are put away, I’m in daily communication with guides and fly shops for local information, and the potential for epic river days truly exist.

As Big Sky takes a breath at the end of ski season, hardcore anglers welcome the unofficial start of dry-fly fishing. The high-mountain snowmelt stays put, for now at least, and pre-runoff conditions exist on most local rivers, an ideal recipe for hatches and hungry trout seeking tasty surface meals.

Here are the hatches to be matching over the next few weeks:

Blue Winged Olives. This is a general term for an olive-bodied mayfly with blue wings. Blue Winged Olives – or “BWOs” if you want to sound like an expert – make up the family Baetidae. That’s Latin for “What you don’t need to know to catch fish.” BWO nymphs are abundant in most of our area rivers. For springtime angling, fish BWOs in sizes 14-16. They hatch midday, and sometimes later in the afternoon if the previous night was cold.

If the forecast calls for an overcast, calm and drizzly day, expect a very good hatch. BWOs appear like miniature sailboats on the surface, and with a light drizzle, they’re less able to dry their wings off and stay on the water’s surface. Myriad patterns exist for all stages of BWOs; however, in spring a well-presented Parachute Adams usually gets the job done.

Skwala, nemoura, capnia, and black stoneflies. For years, fishermen on the west side of the state have known about the early season skwala stonefly emergence. Only recently have anglers in our region been turned onto it. Although our early season stoneflies aren’t out as long as those in warmer parts of the state, these offer an opportunity to anglers wishing to cast bigger dry flies.

Skwala stoneflies are size 10-14 and a dark-bodied pattern is the best imitation. Nemoura stoneflies are small, and best imitated with a black to reddish-black fly in a size 16-18 – I like a Royal Stimulator or a Stimi-Chew Toy. Capnia stoneflies are similar to nemoura, and often referred to as “snow flies” because they tend to hatch during spring snowstorms.

March Browns and Drakes. Although not as common as BWOs and caddis, these bugs are noteworthy, large mayflies. Often in size 10, they hatch sporadically on most of our rivers. Similar to BWOs they hatch later in the day, but typically not in a large emergence. Drakes in April will most likely be gray, as the green ones appear later in May or June. Most larger Parachute mayfly patterns in size 10 and 12 will work.

Mother’s Day caddis. We are weeks away from Mother’s Day, but the fish don’t know that. Plus, with our warmer-than-average spring, caddis on our local rivers might pop sooner than expected. The Mother’s Day caddis hatches on the Lower Madison and Yellowstone rivers are well-known events, but they’re very difficult to plan for – like most hatches, they’re entirely weather dependent. Because it’s dam controlled, the Lower Madison is less susceptible to runoff than the Yellowstone, making the caddis hatch a little easier to fish.

On the Yellowstone, warm weather is a blessing and a curse. Warm water temperatures are needed to kick-start the hatch; however, runoff commences if it’s too warm. The ideal scenario on the Yellowstone sees daytime highs in the mid to upper 60s F – even a day in the 70s – but nightly lows must hover around freezing. I prefer fishing a two-fly rig for most early season caddis situations and will tie a higher-floating fly first, such as a Goddard caddis or a Bloom’s HiVis, trailed with any CDC emerger pattern – my favorite is a CornFed Caddis.

With ski season coming to a close and Big Sky going into snooze mode for a few weeks, dry fly anglers will rejoice in the available opportunities. Our spring hatches are also ideal for those needing a break – most hatches occur midday or later, so there’s plenty of time for extra sleep, or one more cup of Joe before heading out.

Pat Straub is the author of six books, including “The Frugal Fly Fisher,” “Montana On The Fly,” and “Everything You Always Wanted to Know About Fly Fishing.” He and his wife own Gallatin River Guides in Big Sky and along with a business partner, operates a guide service on the Missouri River.