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Horsefly River: Upper Mainstem – October 10, 2021

J. Hillaby and E. Gruhs

Background

Our version of the “upper” mainstem is actually downstream of the big falls at 127 km in order to focus on finding some spawning fish.  While this is only a short section of a very large watershed, our hope was that in the middle of October there may be some salmon species, other than sockeye, that we could find.  Since fall is upon us, we grabbed the bear spray and headed out a little earlier in the day.  The true “upper Horsefly” is an expedition in itself, and will be on the list for another time.

We visited 3 sites:  the Sucker Creek confluence near the 106 km board, an unmarked boat launch at about 117 km, and the McKinley Creek confluence just downstream of the 500 Road bridge over the Horsefly.   Our objectives were to look at the mainstem channel at these locations and see what we could find – hopefully some fish, alive or dead.

Take home messages

At the Sucker Creek confluence the mainstem was sprinkled with large boulders, root wads, a mix of substrates, mature forest and generous riparian plant zone on both sides – a complex and productive habitat that should support both spawning and rearing salmonids.  Lower Sucker Creek itself seemed to have been subject to some massive movement of gravel/cobble which has elevated the stream channel enough to limit fish movements to all but flood conditions.  Perhaps a more detailed survey is warranted.

The second site at the river boat launch was the briefest, as we were not prepared to do much wading in what was a deceptively deep and swiftly flowing channel.  We could not detect any turbidity, despite the dark appearance of the water, the pH was fairly high in the basic range (7.93), ORP at (-40), and conductivity a little lower at (87 µs or microsiemens/second).  It was notable that for the first time this year, the water temperature (6.2 – 6.8 oC) was warmer than the air temperature (5.5 oC).  We also noticed a mat of vegetation at this site – I know it as Elodea canadensis, a native vascular plant that can get established on quiet, muddy bottoms (right).  This is not a species of concern, but its presence is a reminder that this is a fine place for one of our “clean, drain and dry” signs provided by the Invasive Species Council of B.C.  A boat launch is a boat launch. 

In the lower McKinley, just upstream of the Horsefly River confluence, we found fish.  Several that were smaller and we could not identify (probably resident char or trout) and one spawned out female sockeye that is now a YouTube star.  The white patch on her head is an injury with a subsequent fungal infection.  You will also note the abraded tail, and lethargic swimming – she has spawned and is close to death.

What’s next?

As a larger river, the Horsefly can be considered to have very different characteristics as you travel along the mainstem.  It would be useful to identify specific reaches and do more detailed surveys on representative areas in order to comment on their relative ecological health.  It is not all the same. 

Next week – Either Sucker Creek upper and lower sites (if the weather is good), OR the two Harpers Lake tributaries (if the weather is poor).  Please see us on Sunday, October 17th, outside SAWS at 11 am.