How Do Trout Change Color?

Hi everyone!

As our trout are adapting to their stream environments, they will undergo some color changes to help them blend in and survive in their environment. These changes will take on three major forms of camouflage:

Can you find the 17 trout in this picture?

1. Concealing - the trout will adapt its color to mimic the colors in its environment
2. Confusing - the trout will adapt its markings to mimic the patterns in its environment
3. Countershading - the trout might differentiate colors on its ventral and dorsal sides

The trout make these changes using color cells called chromatophores. A chromatophore cell has a central pigment granule that is a certain color. The color changes size in response to the trout's hormones. For example, if the trout's eyes sense that its stream environment is mostly yellow, hormones will release that inform yellow chromatophores to expand and cause the trout to appear that yellow color. 

While the color change in a trout is far from instantaneous, it does allow a trout to move between environments and to differentiate between seasons. 

Here is a worksheet with an outline of a trout, think about an environment or season that your trout might live in and color your trout to camouflage. You can share your drawing here or on our Facebook page.