When we talk about the rainbow trout, the main cause of different skin color can totally be depended upon the genetic differences as well as strains.
Description about darkness of rainbow trout
The rainbow varies a lot, but you usually see some sort of stripe, it could be an incredible red slash. Some are very silvery, some are darker, could depend on diet and their home water.
Like some other trout species, rainbow trout are native to the North American region. There are two types of rainbow trout, such as the common types and the steelheads. The first one lives in ponds, rivers, and lakes. Steelhead trout are rainbow trout species that can go to the sea for food and return to freshwater streams or rivers to reproduce offspring.
Rainbow trout can be identified by their bright colors. However, the most important factor that helps in the identification is its tail, which is broad and square in appearance. Rainbow trout have black dots on their body and fins. Steelhead trout share a lot of similarities with the regular ones but have slight differences in features. Steelhead trout is larger and live a more streamlined life in the sea.
These fish can reach up to 2.5 feet in length. They prefer cold and clear water. The optimal temperature for rainbow trout ranges between 45 to 60 degrees Fahrenheit. Insects, minnows, crayfish, and other small acquit species are their favorite diet. That’s why you can easily catch them with fly fishing or spinner.
All are beautiful fish. They could be more heavily spotted like here, with a stripe that is more purplish. Also one needs to understand that if the density of stock in fish increases in a particular place, then these rainbow trout become more dark or darkest.