Trout (Oncorhynchus mykiss) is a type of trout and salmonid species originating from cold-temperature tributaries in the Pacific Ocean of Asia and North America. Rainbow trout adults in freshwater streams can weigh between 1 and 5 pounds (0.5 and 2.3 kg), while lake-dwelling and anadromus rainbow trout can weigh up to 20 pounds (9 kg).