The food contents of dolphins, 1, 103 individuals in number, captured under the dipped-wood at the offing of Hamada, Shimane Prefecture, from July, 1955, to October, 1959, were examined (Figs. 1 & 2).
1) The contents of the alimentary canal have been classified into a great many different kinds, which are Pisces, Crustacea, Mollusca, Coelenterate and Algae, and the first is parti-cularly dominant in frequency of appearance and in wet weight amounting nearly 90% of all, respectively (Table 1).
2) The alimentary canal contents are nearly limited to the creatures of surface layer, and it has been found that there is the limit on body length of those of median layer, Sar-dinops melanosticta, Trachurus japonicus and so on.
3) Body length of food fishes varies from 1cm, or thereabouts, to 34cm., but it may morphologically be divided into two discontinuous groups (2-4cm & 10-15cm).
4) The median sized food fishes (10-15cm) are most prominent in frequency of appearance and in wet weight.
5) Larvae of Monacanthidae, Upeneus bensai, Engraulis japonica and Oplegnathns fasciatus have abundantly been found in young forms, which had directly been swallowed by dolphins.