1. Troutnut Forum
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2. Fly Fishing
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3. Color variations in Rainbows

Last Saturday I played a young rainbow that was partly silver & partly dark green. I've encountered both colorations B4 but not a fish with a mix of the dark & silver. Is this a dietary influence, a morph change or an indicator of a health problem?

Fishmutt

Most likely has to do with ambient lighting the fish was in.

Partly dark green on top, and silver on the bottom? Natural camo if that is the case.

Actually the colors were sharpley divided but erratically around the girth.
Very pronounced. Looked kind of like a birthmark boundary.

Fishmutt

Rainbows come in all kinds of different patterns. Ive taken photos of almost all my decent sized fish and its amazing to see the difference. Time of year, mating, water color, etc. all have an effect on their color IMO

I agree. Ive caught rainbows with the silvery coloration dominant and pronounced as well as the variation where it looks more greenish and the iridescent stripe is kind of more cutthroaty looking because its a deeper more pronounced color as well.

Individual and environmental differences are strong influences on appearance but genetics also comes into play. Various strains have developed distinct looks while adapting to their environments over time. Native races in their native habitat tend to be more uniform in their appearance. Introducing multiple cultured strains into non-native environments produces a lot of variation as some specimens will display traits of different parentage more strongly. The look FM is describing (spotted dark green back, plain silver without spots below the median) is typical of the Kamloop strain (lake dwelling rainbows from BC) and most steelhead races. The McCloud race (used by the culturists that started it all) are heavily spotted below the median and are more brightly colored.