The food habits of the white croaker, Argyrosomus argentatus (HOUTTUYN), which is an important resource for fishery in the Seto Inland Sea, were investigated through the qualitative and quantitative analysis of the stomach contents. This study, based on 216 fishes caught in the Seto Inland Sea that had a standard length from 20mm to 244mm, is one of the serial studies on the fishery biology of the white croaker in the Sea.
General conclusions obtained in this study are as follows:
1) Food organisms occurred in the stomach were fish, shrimp, amphipoda, polychaeta, cephalopoda, cladocera, brachyura, stomatopoda and isopoda. But fish and shrimp constituted the main food items.
2) In frequency of occurrence, the main food organisms were fish for 52 percent of the 216 stomachs, 78 percent was shrimp and 17 percent were other organisms. Alpheus sp. and Crangon sp. which were the dominant species in shrimp occupied both 18 percent.
3) By numerical method, 21 percent of food organisms of 216 stomachs was fish, 49 percent Crangon sp., 7 percent Alpheus sp. and 19 percent other shrimp.
4) The 113 stomachs contained a total weight of 154, 836mg of food organisms, of which 65 percent was fish, 20 percent Alpheus sp., 2 percent Crangon sp. and 7 percent other shrimp.
5) The main food organisms of young white croakers above 20mm and under 60mm in standard length were shrimp, and the most common was Crangon sp.. Crangon sp. occupied 61 percent of food organisms in stomachs in frequency of occurrence, 84 percent by numerical method and 78 percent by gravimetric method.
6) The white croaker above 60mm and under 170mm in standard length has preied mainly upon shrimp and fish. In frequency of occurrence, shrimp occupied 87 percent and fish 50 percent. Alpheus sp. was dominant in shrimp and occupied 27 percent in 87 percent. By numerical method, shrimp occupied 57 percent (Alpheus sp. 19%) and fish 34 percent. By gravimetric method, shrimp occupied 53 percent (Alpheus sp. 38%) and fish 36 percent.
7) The main food organisms of the adult above 170mm in standard length were fish. The fish occupied 91 percent of the stomach contents in frequency of occurrence, 82 percent by numerical method and 94 percent by gravimetric method.
8) The length of the prey in the stomach of the white croaker increased as the length of the predator himself increased. The total length of the largest prey in the stomach was about one-third of the standard length of eater himself, generally.