For me the spring salmon fry migration is the high light of springtime fishing. It is mostly brought about by cutthroat feeding on large schools of migrating chum fry. It's both frequently exciting and just as frequently exasperating.
Let's have a look at the fry. First a good look at a sample dead fry I found at the waters edge just a couple of week's ago:
They are relatively long & thin. The flanks are silvery, the back a drab olive and are marked with darkish bars above the dorsal fin. The eyes are prominent. BTW if you look closely at the rear 1/4 or so of the fish you should see a triangular lesion. Perhaps that is why this fish died. I have also seen Siamese Twin fry and saw albinos in the tanks at the Chehalis hatchery back in the 80s.
In the past I sampled fry from the stomachs & measured them. They were near uniformly about 35mm which is much longer than the typical fly patterns used to imitate them. Have a look at this photo.
When I started fly fishing the typical patterns were English wet flies like silver and teal series. Tied down mylar minnows with a body of silver mylar tube and a wing of mallard flank tied down at the back was a recent innovation. Perhaps the barring on the teal and mallard flank feathers imitated the barring on the fry. If you get to view the fry from the top, at close range the bars are quite noticeable.
My favorite was the Something Else:
Hook: #6 1x long nymph hook
Thread: white & olive for the head only
Body: pearl mylar tube wound with clear swannudaze or vinyl rib
wing: white polar bear or sub with rolled mallard flank dyed wood duck
Over wing: a few strands of pearl or silver crystal flash
head: Olive thread
eye: painted or 3mm stick on.
when I first started fishing this fly was super effective and I thought this fishery was dumb easy. Unfortunately the fish soon dashed my feelings as within a few seasons they demonstrated how maddeningly selective they could be. That was what lead me to sampling stomach contents and I added a long thin white tail to the Something Else and was again in business or so it seemed.
I'll still keep the Something Else in my fly box as it is a good general minnow pattern. Another good alternative is a sparsely dressed Rolled Muddler either in natural or with both the mallard flank and deer hair dyed light olive.
I follow up with more patterns and some suggestions how to anticipate this fishery and other tactics.