I
managed to hit a couple of central Alberta trout streams over the weekend. Water
conditions were good; and as expected there were several species of winter stoneflies
hatching along with a few midges. I did see a few fish rise but my dry fly
offerings were consistently ignored. Nymphs produced similar results and it
wasn’t until I switched to a marabou sculpin on a fast sink tip that I hooked
my first good fish.
|
A nice bank where big browns like to lurk |
As for the winter stoneflies, the usual suspects
were out and about – most of them in the size 16 range.
|
Mesocapnia projecta |
|
Capnia sp. |
There
was one unexpected stonefly – one that, due to its life history, is rarely
available to trout. Isocapnia integra
larva prefer to live deep in the gravel; an area we refer to as the hyporheic
zone. Here the only water flow is from stream water that seeps under the gravel
through small aquifers, sometimes resurfacing again mid-stream, or at small
spring like upwellings at the tail end of a gravel bar. It was at one of these “springs”
that I spotted these stoneflies emerging – they were only in direct proximity
to where water was seeping out of the ground.
|
Isocapnia integra adult female and nymphal exuvia |
Females
have reduced wings (brachypterous) and males lack wings entirely, so once they
emerge they do not travel far. It is likely that they mate and lay eggs right
at the spring; and the nymphs re-enter the hyporheic aquifer upon hatching.
There have been reports of fully winged morphs – a strategy that may allow them
to disperse when habitat conditions deteriorate.
|
Isocapnia integra just starting to emerge |
In Alberta this
species has been reported from Waterton and Banff national parks – they have not
yet been documented this far from the mountains.
|
Isocapnia integra adult female |
I also revisited a spring creek that used to produce some large browns years ago, but the upper end was still locked in ice. I did not spot any fish in the lower end on this trip but I know they are there.
|
A small Alberta spring creek that beckons further exploration |
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