Catch and Release Fishing information provided by the National Park Service.
The National Geographic website provides the following information on Rainbow Trout.

The rainbow trout is native only to the rivers and lakes of North America, west of the Rocky Mountains, but its value as a hard-fighting game fish and tasty meal has led to its introduction throughout the world.

Rainbow trout, also called redband trout, are gorgeous fish, with coloring and patterns that vary widely depending on habitat, age, and spawning condition. They are torpedo-shaped and generally blue-green or yellow-green in color with a pink streak along their sides, white underbelly, and small black spots on their back and fins.

They are members of the salmon family and, like their salmon cousins, can grow quite large. They average about 20 to 30 inches (51 to 76 centimeters) long and around 8 pounds (3.6 kilograms), but can grow as long as 4 feet (1.2 meters) and weigh up to 53 pounds (24 kg).

They prefer cool, clear rivers, streams, and lakes, though some will leave their freshwater homes and follow a river out to the sea. These migratory adults, called steelheads because they acquire more silvery markings, will spend several years in the ocean, but must return to the stream of their birth to spawn.

Rainbow trout survive on insects, crustaceans, and small fish. Their populations are healthy worldwide and they have no special status or protections. However, they are now considered a non-native pest species in some areas where they have been introduced.