Steller's sea eagle mainly feeds on fish. Their favored prey in river habitats are salmon ("Oncorhynchus" spp.) and trout. Among these, pink salmon ("O. gorbuscha") and chum salmon ("O. keta") are reportedly favored, sometimes intensely supplemented by grayling ("Thymallus" sp.) and three-spined stickleback ("Gastrossteus aculeatus"). While pink and chum salmon average approximately in mature mass, respectively, Steller's sea eagle not infrequently preys on fish up to . In coastal areas, nesting eagles may feed on Bering wolffish ("Anarchichas orientalis"), "Hemitripterus villosus", smooth lumpfish ("Aptocyclus ventricosus") and "Myoxocephalus" spp. Like most "Haliaeetus" eagles, they hunt fish almost exclusively in shallow water. Relatively large numbers of these normally solitary birds can be seen congregating on particularly productive spawning rivers in August through September due to an abundant food supply.