North America’s main hatch event

Come hell or high water, one of the more faithful June “bustings out all over” along some Central Alberta trout streams is the annual hatch of the Salmon fly (Pteronarcys californica), our largest stonefly.

Come hell or high water, one of the more faithful June “bustings out all over” along some Central Alberta trout streams is the annual hatch of the Salmon fly (Pteronarcys californica), our largest stonefly.

In rare years, the event can take place in May, and that seemed possible this year, with no monsoon in sight and the water warming to hatching temperatures. Along the streams, things seemed normal for the first season in about the last three or four. The Western March Brown mayfly appeared just when it should, along with the wild Clematis, and some anglers were reporting trout rising to something invisible (the very dark March Brown can be very hard to see on the water, especially under overcast skies), but being able to catch them with a #12 or #14 Adams.

Then anglers started getting fast action using big, black, weighted stonefly nymphs, a clear indication that the Salmon fly nymphs were moving to the banks and shores, preparing to emerge, “hatch,” into winged adults, and mate. Then we’d all just have to for the return of the females, en masse, to the water, fluttering on the surface, to deposit their eggs, driving trout to gluttony and fly fishermen berserk in what is arguably the main hatch event of North American fly fishing.

But, as so often happens with the Salmon fly hatch, the monsoon suddenly blew in and roiled rivers and streams into torrents of peanut butter. The big bugs don’t care, perhaps would prefer, if they were sentient, that the trout can’t see, and thus eat them. When no rising trout are to be seen, frustrated anglers, thankfully, are not tempted to risk wading high, dark, and dangerous waters.

Experienced hatch chasers tell me I am plain lucky to have fished a dozen perfect Salmon fly hatches in 50 years, three times on Montana’s fabled Madison River, once on our Crowsnest, and eight or nine times on Central Alberta brown trout streams.

Fishable water or not, I never tire of watching, the hatching process, and run for my medical photography equipment whenever, usually as dark falls, I notice the massive migration of mature Salmon fly nymphs. The glistening black, five-cm long lobster look- alikes, crawl from the water that has been their home for three or four years (and through many underwater molts as they grew) and onto boulders and streamside vegetation for the final molt-“hatch,” into the winged adult stage: another of the great miracles of the Manitous.

If an arriving nymph does not quickly find a suitable anchor point, it will re-enter the water, then climb out and up elsewhere. I surmise they must keep their chitin, their nymphal skin, wet until they are ready.

When the nymph finds a spot to its liking, it gropes for the best foothold. Then the creature becomes quiet, almost prayerful, like a weight-lifter before the lift. Gripping the rock, reed, or branch with its claws, the nymph humps its body, again and again, putting tremendous pressure on the centre line between its wing pads.

Slowly, a white crack appears behind the head, then, as the crack widens, a blaze orange spot, the head markings of an adult salmon fly, glows in the gloom. Slowly the huge adult hauls itself through the small hole in its nymphal case to stand atop the shuck, drying pinkish, clumped, vertical wings that eventually unfold, flatten over the back, and harden into the smoky-grey, nylon-stocking appearance of the adult Salmon fly wing.

Light and wakefulness have always failed me before I have seen completion of the wing hardening, but from emergence of the nymph from the water to emergence of the adult from the case, takes approximately 15 minutes in each insect. By mid-morning after one of these events, empty nymphal shucks cling to rocks, reeds and branches, and it is impossible to seine a live, mature, Salmon fly nymph from the water.

When the insects are dry and their wings fully hardened, they fly up into streamside trees and bushes where the sexes locate each other with a drumming procedure and mate.

For anglers, the wait can be excruciating for the main fishing event, when the females fly en masse to the water to lay their eggs and start the whole life cycle over again.

On one of my Montana trips, snowy, cold weather kept the gravid females “grounded” in the trees and bushes for 10 days. One year on Prairie Creek, they hung in the trees for a week, and then flew the egg-laying run at midnight.

World-wide there is a very small group of photographers who specialize in photographing aquatic insects of interest to fly fishermen.

Up until recently my 20 images of the progression of the Salmon fly emergence sequence from start to finish was the only one I was aware of; and it has never been published intact because of space limitations and because I was holding it for another book.

Fortunately, the current issue of Fly Fisherman magazine carries excellent shots of some of the stages of the hatch from Arlen Thomason’s book, “Bug Water.”

Bob Scammell is an award-winning outdoors writer living in Red Deer.