Why do salmon turn red when they spawn?

Salmon don't actually turn red when they spawn. They actually become more colorful overall, with red being a prominent color, especially in males.

Here's why:

* Hormonal changes: During their spawning journey, salmon undergo hormonal changes that trigger the production of carotenoid pigments. These pigments are responsible for the vibrant red, orange, and even green colors that appear on their skin and flesh.

* Attracting mates: The bright colors are a mating display that attracts females. The more vibrant the colors, the healthier and stronger the male is perceived to be, making him a more desirable mate.

* Camouflage: In some species, the reddish color also helps the salmon blend in with the gravel beds where they lay their eggs.

* Fighting rivals: In some cases, the brighter coloration can also be used in aggressive displays to ward off competitors.

It's important to note that not all salmon species develop the same color intensity during spawning. Some species may have more pronounced red colors, while others may have more orange or green hues.

The specific color changes and the degree of intensity can vary greatly between different species and even within the same species depending on factors like age, health, and diet.