According to a study done by Simon Fraser University researchers, adequate water flows during the summer can be important for the Chinook salmon population in British Columbia’s interior.
The researchers looked into how the Nicola watershed’s water flows affect early summer-run Chinook salmon. To investigate 22 years of fluctuation in Chinook salmon productivity, the researchers employed an advanced time-series model.
They discovered that the flow during August, when Chinook are rearing as juveniles, was the most important predictor of productivity after accounting for ocean survival and density dependency.
Higher August flows during adult spawning and migration are also expected to improve productivity, whereas lower flows are connected to a decline during this time.
Given the region’s watershed activities and climate change, the findings could aid in water management. The findings were just published in Ecological Solutions and Evidence, a peer-reviewed journal.
This data is helping to inform ongoing watershed planning and on-the-ground action in the Nicola by the five Nicola Bands and the Province. Science such as this, as well as traditional knowledge and other sources of expertise, are guiding real change on the ground to steward this watershed.
Leona Antoine
“We found that August flows during juvenile rearing had the greatest impact on Chinook productivity out of any factor; the effect was very large,” says the study’s lead author, Luke Warkentin, who carried out the project as part of his master’s research in SFU’s Salmon Watersheds Lab, in collaboration with scientists from Fisheries and Oceans Canada. “If there isn’t enough water during the summer, Chinook populations tend to decline.”
Cohorts that had 50% below average flows in August of spawning and rearing had a 29% reduced output on average.
Changing flows and cumulative effects
According to examinations of long-term flow data, Nicola River flows in August have fallen by 26% on average during the last 100 years.
“These long-term changes are probably the cumulative effect of climate change, water withdrawals for agricultural and other uses, and land use such as forestry,” says SFU biological sciences professor Jonathan Moore, the paper’s co-author.
Managing flows for people and fish
Many various human activities, such as water withdrawals for agriculture, dam operations, and forestry, as well as climate variability, influence river flow. Fish survival and productivity are affected by seasonal changes of water flow.
However, determining how much water-specific rivers require to sustain or rehabilitate fish and their fisheries can be tricky. The findings of this study can be used to guide environmental flow management in systems with diverse demands on water systems, such as the Nicola River.
In 2021, devastating floods and a heat dome hit this part of B.C., breaking records and causing significant damage to people and property.
“This data is helping to inform ongoing watershed planning and on-the-ground action in the Nicola by the five Nicola Bands and the Province,” says Leona Antoine who helps lead the Nicola Watershed Governance Project, and is associated with the Scw’exmx Tribal Council, not involved in the study.
“Science such as this, as well as traditional knowledge and other sources of expertise, are guiding real change on the ground to steward this watershed.”
