Study finds river flows linked to highs and lows in endangered Chinook salmon population

Adult Chinook salmon in the Nicola watershed. Credit: Jonathan Moore

A study by researchers at Simon Fraser University found that sufficient water flows during the summer can be critical for a Chinook salmon population in the interior of British Columbia.

Researchers studied how water flows in the Nicola watershed affect Chinook salmon in early summer. The team used an advanced time-series model to understand 22 years of variation in Chinook salmon productivity. After accounting for ocean survival and density dependence, they found that flow in August, when chinook spawn as juveniles, was the most important predictor of productivity. Higher flows in August during spawning and adult migration also likely boost productivity, while lower flows during this time are linked to decline.

The results could help inform water management given watershed activities and climate change in the region. The results have just been published in the journal Ecological solutions and proofs.

“We found that August flows during juvenile rearing had the greatest impact on Chinook productivity, of all factors; the effect was very large,” says lead study author Luke Warkentin, who carried out the project as part of his master’s research at SFU’s Salmon Watersheds Lab, in collaboration with scientists from Fisheries and Oceans Canada. “If there is not enough water during the summer, chinook populations tend to decline.” On average, cohorts that experienced 50% lower than average August spawning and rearing throughputs had 29% lower productivity.

Study finds river flows linked to highs and lows in endangered Chinook salmon population

Juvenile Chinook salmon in the Nicola watershed. Credit: Jonathan Moore

Changes in flows and cumulative effects

Over the past 100 years, August Nicola River flows have declined by an average of 26%, according to analyzes of long-term flow data.

“These long-term changes are likely the cumulative effect of climate change, agricultural and other water withdrawals, and land uses such as forestry,” says Jonathan Moore, professor of biological sciences at SFU. , co-author of the article.

Manage the flow of people and fish

Water flows in rivers are controlled by many different human activities, such as water withdrawals for agriculture, dam operations and forestry, as well as climate variability. Seasonal water flow patterns can affect fish survival and productivity. Yet it can be difficult to know how much water certain rivers need to maintain or restore fish and their fisheries. The results of this study can help guide the management of environmental flows in systems with multiple water demands, such as the Nicola River, and elsewhere.

In 2021, this area of ​​British Columbia experienced catastrophic flooding and a record-breaking heating dome that caused significant damage to people and property.

“This data helps inform ongoing watershed planning and on-the-ground actions 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 like this, along with traditional knowledge and other sources of expertise, is guiding real change on the ground to manage this watershed.

Survival of migrating juvenile salmon depends on stream flow thresholds

More information:

Luke Warkentin et al, Low summer river flows associated with low Chinook salmon productivity in a watershed with changing hydrology, Ecological solutions and proofs (2022). DOI: 10.1002/2688-8319.12124

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Study finds river flows linked to highs and lows in endangered Chinook salmon population (2022, January 21)
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