Rainbow trout and steelhead are ray-finned fishes in the salmon family, and they are one of the top sport fish in North America. Rainbow trout and steelhead are the same species, but they have different lifestyles.
Steelhead are anadromous—meaning they spend part of their lives in the sea before going to rivers to breed—while rainbow trout spend their lives mostly or entirely in freshwater. Because of their different lifestyles, rainbow trout and steelhead are different in appearance, most noticeably in size and color. Rainbow trout derive their name from their beautiful, multi-hued coloration. Their bodies are blue, green, or yellowish, shading to silvery white on the underside, with a horizontal pink-red stripe running from the gills to the tail and black spots along their backs. Steelhead are generally more streamlined in shape and silvery or brassy in color as adults, earning them their name.
Adult rainbow trout and steelhead range in size. They can reach 45 inches in length, but are usually much smaller. They can weigh more than 50 pounds (22 kilograms), but a more typical weight is 8 pounds (3.6 kilograms). Because steelhead spend two to three years in freshwater followed by two to three years in the ocean, they are typically larger than rainbow trout, which live all of their lives in fresh or sometimes brackish water.