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Horsefly River: Lower Mainstem – September 23, 2021

J. Hillaby , H. Englund and E. Gruhs

Background

In Horsefly, no fall outing is complete without a close look at the Horsefly River itself.  We were fortunate to have volunteer Phil Hartman take a fabulous drone video of spawning sockeye, taken about September 18 – 19th, off the Mitchell Bay Road.   

This is irresistible.  Streamkeepers field protocols allow us to undertake stream surveys on an overview as well as detailed level.  We can also plan on conducting systematic counts of migrating salmon in streams.  So, the purpose of today’s survey was preliminary:  to locate these spawners from the stream banks and see how they were using physical habitat features in the stream channel (e.g. holding pools, cascades and riffles, cut banks, whatever).  Most importantly, we needed to assess how we could get in there to learn more, safely.

Take home messages

The Horsefly is a big river – a few days of rain raised the water level substantially, eliminating some of the shallow gravel bars that may have made access safer.  The water was also noticeably turbid (not measured) and the high overcast conditions put a glare on the water that was difficult to get past when viewing fish under the surface.  We saw some fish near the Horsefly River Flats rec. site but not clearly enough to relate these observations to the stream channel habitats.  Evidently, we need better discharge information, faster response timing, improved gear, and a boat.  We were asked to look for pink salmon but saw none.

Horsefly River Flats site where spawning salmon were observed

Upstream at the Creek Bridge

Travelling upstream, toward Horsefly, we saw substantial sand piles at the Rat Creek bridge.  Subsequent upstream stops at the 8 km hill on the Mitchell Bay Road and on the riverbank at about 500m downstream of “the steps” which showed us some potential sources of the sand.  A review of the maps indicates that Hobson’s Hydraulic Mine operated in this vicinity from 1890 to 1899, using a massive jet of water to erode bank and flood plain material to extract gold.   Ernie Gruhs also identified the location of some derelict horizontal mine shafts, tucked into the bank perpendicular to the mainstem.

Looking downstream, high, erodible banks on the right bank of the river

The left bank directly opposite appears very different

What’s next?

We will continue looking at the Horsefly River mainstem, shifting focus to the upstream areas where there should be less channel instability, and where we may be able to find some coho salmon.  This species migrates in October and November and is more difficult to identify without a directed effort.  

Next field trip – We will have a short break and then continue slightly earlier in the day.  Please join us on Sunday October 10th, be outside SAWS at 11 am.  Bring your boots, and some lunch.