River flows linked to the ups and downs of imperiled Chinook salmon
population

Date:
January 21, 2022
Source:
Simon Fraser University
Summary:
A study has discovered that sufficient water flows during summer
can be critical to a Chinook salmon population in the interior of
British Columbia.



FULL STORY ==========================================================================
A study led by Simon Fraser University researchers has discovered that sufficient water flows during summer can be critical to a Chinook salmon population in the interior of British Columbia.


==========================================================================
The researchers investigated how water flows in the Nicola watershed
affect early summer-run Chinook salmon. 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 discovered that the flow during August, when Chinook are rearing as juveniles, was the most important predictor of productivity. Higher August flows during adult spawning and migration also likely boost productivity,
while lower flows during this time are linked to decline.

The results could help to inform water management given watershed
activities and climate change in the region. The findings are newly
published in the journal Ecological Solutions and Evidence.

"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 masters 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." On average, cohorts that experienced 50 per cent below
average flows in the August of spawning and rearing had 29 per cent
lower productivity.

Changing flows and cumulative effects Over the past 100 years, Nicola
River flows in August have decreased by 26 per cent, on average, based
on analyses of long-term flow data.

"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 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. The seasonal patterns of water flow can impact the survival
and productivity of fishes. Yet, it can be difficult to know how much
water particular rivers need in order to sustain or recover fish and
their fisheries. The findings from this study can help guide management
of environmental flows in systems with multiple demands on water systems,
such as the Nicola River, and elsewhere.

In 2021, this region of B.C. suffered catastrophic floods and a heat dome
that broke records and caused substantial harm 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." ========================================================================== Story Source: Materials provided by Simon_Fraser_University. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Luke Warkentin, Charles K. Parken, Richard Bailey, Jonathan
W. Moore. Low
summer river flows associated with low productivity of Chinook
salmon in a watershed with shifting hydrology. Ecological Solutions
and Evidence, 2022; 3 (1) DOI: 10.1002/2688-8319.12124 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220121145428.htm

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