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From end March to mid May, with the passing of winter, the sun hangs higher and longer in the Canadian sky warming the Bow River Valley. The river is at its lowest point all year and the sun quickly raises its temperature above the critical 45°F point. Downstream from Calgary the ice slowly recedes revealing the drift boat launches. The news of their accessibility spreads quickly through the fly fishing networks. For many, the Bow River fly fishing season has begun.
 
Early Spring Rainbow Early Spring Brown
Since October, the Bow River trout have had somewhat of a limited diet feeding mainly on midges and the odd caddis or water boatman. The San Juan Worm and Wire Midge Pupa have been the fly fishermen's main selection of fly pattern. With the rising water temperature come leeches, skwala stoneflies, scuds, and Blue Winged Olive (BWO) mayflies. As well, terrestrials such as ants, spiders, and the odd cricket concentrate on the south facing slopes of the river seeking the warmth of the sun. This new life opens up many new fly patterns to the fly fisherman.
Two specific early spring hatches are worthy of note. The first of the yearly mayfly hatches – the BWO; and, the first of the larger stonefly hatches - the Skwala.
  
Bow BWO Nymph BWO CDC Emerger BWO Dry Fly
The BWO mayfly is a catch-all name for small blue/grey winged mayflies with olive/grey bodies. They are generally the first mayflies to hatch in the spring. They can be seen swarming above and near the river banks. The BWO can be fished throughout all stages of development. A Flashback Pheasant Tail or Bow BWO represents the swimming nymph, a BWO CDC Emerger represents the emergent stage, and a BWO dry fly pattern represents the dun. Keeping the patterns small from hook size 16 – 20 is key.
  
BWO Olive Nymphs
To fly fish the BWO nymph, set up a dropper combination off of a dry line. The lead fly should be something like a weighted Bead-head Hare's Ear. The trailing fly, being a Bow BWO or Flashback Pheasant Tail nymph. Cast upstream into the shallow riffles letting the rig drift down over ledges, drop-offs, or into holes. The weighted bead-head lead fly should be enough to drag both flies down into the hole naturally. High stick the nymphs through the riffles and into the hole. The takes can be quite subtle so be prepared to strike at any unnatural movement of your indicator. The BWO CDC Emerger can be fished in the same fashion as the nymph or tied in as a dropper to a BWO dry fly and presented to rising trout.
  
GSFF Skwala Top GSFF Skwala Bottom GSFF Skwala Dry Fly
There appears to be little discussion about the Skwala stonefly hatch on the Bow River in the fly fishermen circles. Cooper, my golden retriever, brought them to my attention one spring while we were fishing a rocky outreach 45 minutes upstream of McKinnon Flats. Fishing was slow so we took a break to eat lunch and think things through. Cooper was over-turning rocks chasing something that was seeking refuge. Crawling through the rocks were numerous ¾ to 1 inch stoneflies. They had an olive underside and dark reddish brown back. This discovery lead to what followed as one of the most memorable and productive days on the river.
Cooper
What seemed odd about these stoneflies was that their wings were only half developed. I later learned that, typically, the short winged skwalas are male. They crawl up on trees and shrubs on the shore line, make some kind of noise, and entice females to fly to them and mate. Once mating is complete, the females return to the water in the mid-afternoon and evening skipping across riffles depositing their eggs.
On the day that Cooper first discovered the skwalas (the GSFF Skwala nymph had not been invented yet), the best that I could do for an imitation was a trimmed down light olive Bow River Bugger. Fishing the fly though riffles into the slow moving water was deadly. It was working so well that at one point I cast it up the shore line to see what all the fuss was about. Within seconds a rainbow swooped into the shore and the fight was on.
 
Early Spring Fish
With the coming of the warmth from the spring sun the Bow River experiences an awakening. The wildlife around the river begins to stir seemingly celebrating their survival of winter. The fish can be seen in the shallows apparently sunning themselves – perhaps absorbing the sun rays much the same as humans that have rediscovered their patios. When the sun heats the Bow River and the waters approach 45°F, the fish are presented with many new forms of food. The new food sources and the warmth of the water wake them up, so to speak, and they move out of their wintering holes into all parts of the river. This is an exciting time for most fly fisherman. Patterns that match the BWO and the Skwala will help fly fishermen do well in the early spring on the Bow River.
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