Abstract
Stomach contents of the amago, Oncorhynchus rhodurus, collected in Hirakura Stream, Mie Prefecture, were investigated and relation between body size and food of this fish and the phenomenon of size hierarchy are discussed.Smaller fish in body length feed mainly on smaller aquatic insects, such as Baetidae and Ecdyonuridae, while larger ones have a strong preference to larger aquatic and terrestrial insects.During summer, smaller fish have little chance of obtaining terrestrial insects because of the predominance of larger fish which feed on terrestrial insects falling on the water surface.
