The Value of Woody Debris in Streams
- When salmon spawn they displace huge numbers of aquatic insects.
- These insects drift and swim downstream and often settle in pools containing woody debris.
- These are areas where salmon do not spawn so the insects are not disturbed by their spawning activities.
- American Dippers know where the insects are so they often forage for them in the debris piles.
- In winter I have found large numbers of juvenile fish, especially Dolly Varden and coho salmon, concentrated in these piles of woody debris.
- Why would they do this?
- Think about camouflage, some studies show the wood provides some warmth, at the bottom of pools so little current, possible spring areas.
- The value of large woody debris in Alaska's streams is discussed in The value of large woody debris in Alaska's streams by Murphy and Koski