[env-trinity] USFS ScienceFindings: StreamTemp Variability & Salmon

[Sari Sommarstrom]

http://www.fs.fed.us/pnw/sciencef/scifi163.pdf

 

July 2014  Science Findings publication---"Stream Temperature Variability:
Why It Matters to Salmon"

IN SUMMARY

Salmon evolved in natural river systems, where temperatures fluctuate daily,
weekly, seasonally, and all along a stream's path-from the mountains to the
sea. Climate change and human activities alter this natural variability.
Dams, for example, tend to reduce thermal fluctuations.

      Currently, scientists gauge habitat suitability for aquatic species by
establishing minimum/maximum temperature thresholds and relying on mean
temperature readings to establish management priorities. But temperature
effects on salmon are more complex. A new study demonstrates that
temperature variability can affect emergence timing in Chinook salmon,
potentially altering predictions about how these fish may respond to a
changing climate. It also reveals that genetics can make a difference in how
an individual responds to stream temperature variance.

      The study indicates that the commonly used degree-day accumulation
model is not sufficient to predict how organisms respond to stream
temperature. Changes in how the degree days are delivered have the potential
to alter the timing of life history transitions in Chinook salmon and other
organisms. Emerging from the gravel a few days earlier or later could
directly affect their survival due to changes in available food resources,
competition for feeding grounds, or strong currents.

 

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