Steelhead grow up to 45 inches (114 cm) long and weigh up to 36 pounds (16 kg)
Rainbow trout average 7 to 20 inches 918 to 50.8 cm) and 1 to 3 pounds (0.5 to 0.9 kg), but have been taken as large as 36 inches 991 cm) and 51 1/2 pounds (24 kg). The name 'rainbow' comes from the reddish stripe which is often, but not always, present along the side. On the young rainbow trout, there are 10 to 15 short, dark, oval parr marks evenly spaced on its side.
Coastal fish often eat insects, chiefly caddis-flies and black-flies, as well as small fish and salmon eggs when available. Inland fish feed primarily on foods that are associated with the stream or lake bottom and eat a variety of things which vary with the season and the size of the fish. Among other things, young fish eat organisms such as Daphnia and insect larvae, while large fish eat larger items such as leeches, large insects, molluscs, and small fish.
This species comes in many different forms, which can be confusing. Generally, the term 'steelhead' refers to fish which enter the ocean for part of their life, and 'rainbow' refers to the fish which remain in fresh water. Spawning for these fish generally occurs at a regular time each year, but this varies from river to river and lake to lake. Most young
steelhead spend two to three years in fresh water before migrating to sea. They return to spawn near the place they were born after spending two to three years in the ocean. Instead of migrating to the ocean, rainbow trout generally spend several years in a lake before returning to their home stream to lay their eggs. Rainbow trout live in lakes and streams and prefer cool water, less than 70 degrees F, with plenty of oxygen.