The feeding characteristics of the chub mackerel, Scomber japonicus from Jeju Island waters and the Yellow Sea were compared by analyzing the stomach contents. Large and small purse seines were used to collect 1437 individuals from Jeju Island waters and 1066 individuals from the Yellow Sea. The fork length of S. japonicus ranged from 21.0 to 43.6 cm for individuals from Jeju Island waters and 19.6 to 41.5 cm for those from the Yellow Sea. Based on the index of relative importance and variation in stomach contents according to fish size, S. japonicus was identified as a piscivore and a spatiotemporally opportunistic feeder. The proportion of fish in the diet increased as the body sizes of S. japonicus from both Jeju Island waters and the Yellow Sea increased, whereas the proportion of copepods, amphipods, and euphausiids gradually decreased. Differences in stomach content compositions were observed due to interactions between size and location. Thus, the feeding characteristics of S. japonicus are affected by the abundance and composition of prey in its habitat.

In this study, the stomach contents of the crocodile toothfish Champsodon snyderi from the offshore waters of the South Sea of Korea were analyzed to understand their feeding characteristics. Bottom-trawlers in the South Sea of Korea were used to collect a total of 228 C. snyderi individuals with lengths ranging from 3.6 cm to 12.3 cm. Based on the index of relative importance and variations in the stomach contents according to fish size, C. snyderi was identified as a spatiotemporal opportunistic feeder that consumes abundant prey resources in the South Sea of Korea. Although no distinct dietary shift was observed with growth, there was a decreasing and increasing trend in the proportion of amphipods and shrimp consumed, respectively, in association with increasing C. snyderi body size in the nearshore waters of the South Sea of Korea. In addition, differences in the stomach content composition were observed in relation to interactions between season and size. Our findings indicate that the feeding characteristics of C. snyderi are affected by the abundance and composition of prey within its habitat.