Interesting steelhead physiology - Spey Pages
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post #1 of 4 (permalink) Old 04-04-2016, 01:36 AM Thread Starter
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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.
Cool, huh?
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post #2 of 4 (permalink) Old 04-04-2016, 09:26 AM
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This is mediated by visual cues of their surroundings.

I've seen a few Atlantic salmon that had been blinded in one eye that exhibited asymmetrical body colour changes. From above, you could see a perfect division along the length of the body - one side very dark, almost black, and the other normal fall colours. Very cool!
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post #3 of 4 (permalink) Old 04-04-2016, 02:02 PM
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I have heard of this chameleon ability to change color according to environment, but I have never observed it myself. Thanks for sharing.

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post #4 of 4 (permalink) Old 04-04-2016, 11:44 PM
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First time I've ever heard of this in salmonids. Relatively common in tropical species. But a fast change in Salmonids? Its a first to me...

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