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Why do spawning salmon turn red?

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Thanks for this inquiry, which highlights some of the mystery surrounding salmon. Scientists believe that there are several evolutionary benefits associated with this “reddening.” But keep in mind, these are theories, not facts!

1. The colour of love: Red colour helps to distinguish salmon so they become more visible and attractive to potential mates. In this, salmon’s change of colour serves the same purpose as many other animals, birds, and fish across the planet: a dating device.
2. The eggs need it: Different chemicals combine when pigmentation takes place, and some of these chemicals are needed by ripening salmon eggs. The eggs need them to be fertile and viable, as well as to protect them from ultraviolet rays if the gravel covering them is removed. The female salmon’s pigment chemicals get redirected to her eggs, which may explain why females don’t turn as red as males do during spawning.

Fin,

Professor Salmon