The fish occur in the ocean or in lakes; adults return to the rivers where they were born (Ref. 27547). The young fish emerge in springtime and they usually live in fresh water for 1-2 years (sometimes up to 4 years, Ref. 27547); later they migrate at night to freshwater lakes or to the sea (Ref. 1998). Epipelagic (Ref. 58426). The fish that stay more than two years in fresh water and become sexually ripe without ever going to sea, are called residuals; they never spawn (Ref. 27547). Young fish in lakes and rivers eat mainly insects; they stay almost entirely in deep parts of the river and soon become strongly territorial (Ref. 27547). Upon reaching the sea, the smolts remain close to the coast for a certain time, eating planktonic crustaceans (Ref. 27547). As they grow, they migrate farther out into the sea and hunt larger organisms (Ref. 27547) such as jellyfish, squids and fishes (Ref. 58426). They are hunted by various fishes, birds (mergansers, loons and kingfishers), mammals and lampreys (Ref. 1998).