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    • Parr marks are spots on the body of juvenile fish during their river life.

      They are thought to be for camouflage as they resemble pebbles on the river bottom.


    • Conversely, when spending time at sea, salmonids undergo a morphological change called smoltification, in which their backs turn gray and their bellies turn white.

      This is thought to be due to a countershading effect, whereby they assimilate the color of the seafloor when viewed from above and the color of the sky when viewed from below, making them harder to spot by predators.