Rainbow trout can live in a wide range of habitats from rivers and streams to ponds, lakes and reservoirs. They feed on aquatic and terrestrial insects, fish eggs, fish fry and smaller fish (up to a third their own length), freshwater shrimp (scuds) as well as crayfish and other crustaceans and even plankton. They spawn in the spring, usually April or May, in running water. This all applies to Bighorn Canyon and this region of the country, but it is really more complicated than this.