EYES ON THE RIVER
Excerpts from report by Allan Chamberlain, July 2023
Eyes on the Tsolum River (ETR) is a group of individuals and families that walk the Tsolum River and report their observations to Allan Chamberlain, a Tsolum River Restoration Society (TRRS) outreach volunteer and retired Fish and Wildlife Professor.
The information gathered includes fish and other wildlife sightings, water quality data, and general observations about the status of the river and watershed. The findings are summarized periodically and circulated to all of the ETR observers, and other persons and agencies interested in the Tsolum River watershed.
Sharing information creates a better understanding of the Tsolum watershed and the status of its native fish. Using this information, we can identify focus areas for restoration and advocate for best practices for fisheries management, with the goal of improving the well-being of the native fish.
The information gathered includes fish and other wildlife sightings, water quality data, and general observations about the status of the river and watershed. The findings are summarized periodically and circulated to all of the ETR observers, and other persons and agencies interested in the Tsolum River watershed.
Sharing information creates a better understanding of the Tsolum watershed and the status of its native fish. Using this information, we can identify focus areas for restoration and advocate for best practices for fisheries management, with the goal of improving the well-being of the native fish.
Juvenile Salmon and Trout Losses due Low Flows and Extreme Water Temperatures
A number reports of fish mortalities came in from the mid to lower reaches of the Tsolum in early July as flows diminished to a trickle (0.05 to 0.1 cubic meter per second) and water temperatures peaked above lethal levels (26.9 to 28.8 Celsius).
As in the previous two years, dead and diseased juvenile salmon and trout were observed, especially in areas in stretches that had little no tree canopy or riparian zone, where water temperatures were lethal. As a result, by the mid July in the barren open stretches of the mid to lower Tsolum, only the occasional small schools of young of the year (YOY) ThreeSpine Sticklebacks were observed.
Due to the very low flows, the “wetted width” of the main stem Tsolum to only a few meters wide in many areas and, consequently many fish were stranded in isolated, drying pools and side channels.
In these areas the salmon fry often die of heat stressed in late afternoon. Many of these fresh mortalities are quickly eaten overnight by crayfish raccoons or mink. Sculpins and larger juvenile trout however, being more bony, take longer to consume and their partially eaten carcasses are often seen the following day. Therefore, because these fish are quickly eaten, it is virtually impossible to make an accurate count the total fish loss from heat shock and/or hypoxia.
Salmonid Migrations to Coolwater Refuge Areas
Many of the Tsolum tributaries and some spawning channels were completed dried by the beginning of July and the main stem of the Tsolum flows dropped dramatically throughout the watershed. Also, by the second week in July, much of the lower Tsolum had reach lethal water temperatures for salmonids. Consequently, it became very challenging to find water suitable to transfer fish that were stranded in drying pools.
Due to the prolonged low flows last fall Coho Salmon Prespawning mortality was high and spawning was many restricted to the lower Tsolum. Subsequently, spring coho fry hatch was low in the spring 2023. As a result, only ~500 juvenile salmonids were observed seeking refuge there this year.
This same refugia in the Lower Tsolum is being monitored again this year In an attempt to increase salmon survival at this refugia, small woody debris (SWD) tree cover and signs warning to notify walkers of this sensitive area, were installed.
Salmon Loss through Entrainment in the Intakes of Pumps
As flows and water levels dropped, some water users moved their intakes closer to deeper channels (Thalweg), possibly making the intake screens are more prone to mechanical damage.
To safe guard against salmon smolts and fry getting suck in the pump, especially when pumping at night, water users please inspect intake screens regularly.