When most people think of trout, the picture in their mind is of the Rainbow Trout. Rainbow Trout are indigenous to the tributaries that flow into the Pacific stretching from Kamchatka, Russia to the northern edge of the Baja peninsula in Mexico.
Fish stocks, primarily from northern California, have been transplanted to many waters around the world where they in some cases grow to huge sizes. They are relatively tolerant to a variety water temperatures and stream habitats which has contributed to their survivability.
Some varieties known as Steelhead spend most of their adult lives in the ocean and esturaries and grow quite large. Steelhead weighing 6-15 lb are not uncommon. Adult Rainbows that elect to remain in fresh water throughout their lives vary in size from ½ lb to 6 lbs in some habitats and can get as large as 20 lbs in others.