Interesting steelhead physiology
Perhaps widely known but previously unknown to me… steelhead perform a chameleon like response to new habitat they enter (apart from secondary sex characteristics that are displayed as they ripen).
The picture shows wild winter steelhead that returned to the N. Toutle collection facility near Mt. St. Helens. We transported them to a creek above a sediment dam to complete (or continue) their life's work.
There is an immediate contrast between them and their surroundings that vanishes in a matter of minutes! It's awesome to watch.
The N. Toutle is heavily ash-laden (as it has been since 1980)… about the color of these fish that we remove from it. They respond to their new surroundings with an effective color change that conceals them.