Spring Excursion

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