06 June 2007

Big Hole River Salmonflies

Well, it's that time of year again: the lilacs are in full bloom on the Butte hill and it's salmonfly madness on the Big Hole River. Despite the severe dewatering going on in the upper reach of the river where grayling live, flows in the middle section of the river are very good. Dave, RTD, and I floated Divide to Melrose Saturday, hoping to see the big flight of western tanagers that often show up about the same time as the salmonfly hatch:
Unfortunately, we saw just one tanager. Lots of other birds -- tri-colored blackbirds, robins, flycatchers, etc. -- were ready for the feast. The salmonfly hatch is about a week early this year, and the migrating tanagers might not adjust easily to the advanced schedules brought by global warming. Salmonfly nymphs live two years before crawling out of the river and taking to the air. Two years ago must have been excellent mating conditions, for this year salmonflies are as abundant as I have ever seen them.

A few days or so before the actual hatch, trout feed heavily on the nymphs that migrate from the rocky fastwater toward shore. It's a good time to fish, especially if you are upriver a few miles from where salmonflies have emerged. All the anglers are downstream, and it's just you and the big, hungry trout:

Even during the hatch itself, the stoneflies spend much of their time hiding out in the willows. First, to shed their nymphal exoskeleton, dry their new wings, find a mate, and (for the females) develop their egg-bomb:

Rain and wind knock a fair share into the water, though, and a good dry imitation can be deadly:

Still, because the mature flies spend so much time hiding out, I find that a nymph or wet-fished dry imitation often produces better than staying on the surface. Fishing on the surface with dries, most of the fish I catch seem to be in the 12" to 15" class. (and mostly rainbow trout):

Fishing below the surface with nymphs or drowned flies, most of the fish I catch seem to be in the 16" to 20" class (and mostly brown trout):

Yesterday, I got on the water in mid-afternoon. Hard rainshowers swept down the valley, with intermittent periods of clearing and almost-sun. During the hardshowers, the salmonflies would retreat deep into the willows. As the rain passed, they would crawl back up toward the tops of the willows. There were always a few crawling around my neck or under the brim of my hat, and enough must have been getting knocked into the water to keep the trout feeding. With the heavy fishing pressure, the trout do seem to get a little wary of imitations. But by prospecting the edges and snags and rocky spots where the boats do not generally reach, there were plenty of eager fish. After a few hours, my arm tired of horsing them out of the heavy water on 3X tippet.

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