The rainbow trout (Oncorhynchus mykiss) is a freshwater euryhaline fish and salmonids of the Marine family distributed natively in the North Pacific Ocean.

Resident adults of freshwater rainbow trout average between 1 and 5 pounds (0.5 and 2.3 kg) in riparian environments, while anadromous and Lake-dwelling forms can reach 20 pounds (9 kg). Coloration varies widely between regions and subspecies.

Adult freshwater forms are usually teal or olive green with heavy black spots along the body. Adult fish have a wide reddish stripe along the lateral line, from the gills to the tail, which is most pronounced in breeding males. The caudal fin is Square and slightly forked. The forms that inhabit lakes and anadromes usually have a silvery color and the reddish Stripe has almost completely disappeared.

Juvenile rainbow trout show Parr marks (dark vertical bars) typical of most juvenile salmonids. In some forms of red band and golden trout, Parr marks are usually preserved into adulthood. Some populations and hybrids of coastal rainbow trout (O. M. Irideus) and Columbia River Red Band Trout (O. M. Gairdneri) may also show reddish or pink throat markings similar to cutthroat trout.

In many jurisdictions, hatchery-raised trout can be distinguished from native trout by Fin clips, usually placed on the adipose fin. Life cycle The rainbow trout, including rainbow trout, generally spawn in early to late spring (January to June in the northern hemisphere and September to November in the southern hemisphere) when water temperatures reach at least 42 to 44 ° F (6 to 7 ° C).

The maximum recorded shelf life of a rainbow trout is 11 years.