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Thursday, February 9, 2012

Pteronarcys californica in Alberta?

I responded to an e-mail from a local fly angler the other day regarding the presence of the stonefly species Pteronarcys californica (aka the Salmonfly) in Alberta. Apparently there is some debate among Alberta fly anglers as to whether or not this species is actually present in the province, and if the many Salmonfly hatches observed by anglers on their local trout streams are indeed P. californica 


There are relatively few records in the scientific literature for P. californica in Alberta. Most of these references are from studies done on the Crowsnest River in Southern Alberta (see for example Townsend and Pritchard, 2001). The paucity of official scientific records for this and other aquatic insect species can be attributed to the lack of province wide sampling required to fully understand the full distribution of most aquatic invertebrates in Alberta. I have personally collected mature P. californica nymphs from Prairie Creek and the lower end of the Clearwater River near Rocky Mountain House. So the short answer to the first question is yes, P. californica is definitely present in Alberta.


Local authors have also written about the legendary Salmonfly hatches on several Alberta trout streams. Of course the P. californica hatch on the Crowsnest River is the most well-known but hatches have also been documented on Prairie Creek, Clearwater River, and the Red Deer River. We also know that P. californica is common on the pacific side of the Rockies, and in streams and rivers on both sides of the Rockies south of the border. In Alberta they are found only in sporadic pockets along the east slopes of the Rockies.

Pteronarcys californica nymph from the Clearwater River

So what about all of the other purported sightings of Salmonflies that have been discussed on local fly fishing forums?

I think much of the confusion comes from anglers erroneously assigning the term Salmonfly to any large dark colored fluttering bug they see streamside. There are several stonefly species in Alberta (not to mention other insect orders) that come close to the size of P. californica, making the potential for misidentification significant. Without considerable experience, a good close look, and sometimes an actual specimen in hand (or under the microscope), these sightings are just not reliable. To further complicate matters, both the adults and nymphs of Pteronarcys californica are easily confused with Pteronarcys dorsata, another more widespread stonefly species found in Alberta. P. californica and P. dorsata are quite similar in appearance, have similar life history and habitat requirements, and sometimes coexist in the same stream. In short, unless you are on a stream known to harbor a population of Salmonflies, any large dark stonefly that you see is unlikely to be P. californica – the only way to be sure would be to collect a specimen and have it identified by an experienced entomologist.



References:
Townsend, G.D. and G. Pritchard (2001). A comparison of methods for analysis of a long aquatic insect life history: Pteronarcys californica (Plecoptera) in the Crowsnest River, Alberta. In: Trends in Research in Ephemeroptera and Plecoptera. Ed. E. Dominguez. Kluwer Academic/Plenum Press, pp. 251-258.

2 comments:

  1. Hello Rob, I truly enjoyed reading this blog. It confirms my own experience with californicas on one of the bodies of water you mentioned in central Alberta. I am also convinced now that dorsata may also be in the mix on this stream. My personal observations maybe wrong but when I do come across the californica hatches they are larger than the dorsatas in size (approx 10mm difference) and its appearance is significant when on the water. I think the dorsatas come off a bit later in the year and they seem to float deeper in the water and are more difficult to seem. I feel the californicas hatch closer to the end of May and into very early June and the dorsata I believe hatch beginning of June to mid June. Can you qualify any of my statements or even correct the timelines based on your experience. I truly enjoy reading your blog.

    Regards,

    Gary H.

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    1. Hi Gary,

      I do know that there can be considerable size variation and overlap for both P. californica (30 to 50 mm)and P. dorsata (25 to 40 mm). I have seen adults of both species from the same stream that were the same size - but in general I would agree that p. dorsata are 5-10 mm smaller than P. californica. As to hatch timing, I have yet to work a P. dorsata hatch but have collected adults of both species in early June.

      Cheers,
      Rob

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