The rainbow trout is a much more versatile feeder. Some of the stomach studies that have been done recently in the States show a completely different pattern of what rainbow trout feed on—from ants to spiders to anything that's available for them to eat. They don't need the volume of food that a salmon requires. Salmon have a four-year life cycle under normal conditions, so they try to eat enough to get them to the fourth year.
On April 23rd, 2012. See this statement in context.