Anadromous (Ref. 5951). Young rainbow trout feed predominantly on zooplankton (Ref. 26523). Rainbow trout of all sizes fed mainly on midge (adults, larvae and pupae). As the fish grew larger, terrestrial prey became the most important food item (Ref. 55755). Possible cohabitation with G. olidus (Ref. 26860). Rainbow trout also have sea dwelling populations known as 'steelhead' (Ref. 6390).