Feeding Habits and Trophic Level of Juvenile Greater Amberjack, Seriola dumereili (Carangidae) in the Southern Waters of Korea

Abstract

Feeding habits and trophic level of juvenile greater amberjack, Seriola dumerili were studied using 170 specimens collected by set net fishery and lure fishing in the southern waters of Korea during July, August, September, October, and November 2022. The size of juvenile greater amberjack ranged from 17.5 to 49.9 cm in fork length. Juvenile greater amberjack was piscivorous predator that feed primarily on fish. We calculated the trophic level as 4.06 ± 0.80 for juvenile greater amberjack. Fishes were the main prey items for all size groups. Juvenile greater amberjack also showed size-related dietary shift from Japanese anchovy to jack mackerel. As the fork length of juvenile greater amberjack increase, the mean weight of prey per stomach tended to increased, while the mean number of preys per stomach was not significantly different. Fishes were the main prey items for summer and autumn. The main fish prey during summer and autumn was Japanese anchovy, but in the autumn, the Japanese anchovy portion decreased, and the jack mackerel portion increased. PERMANOVA analysis was used to examine seasonal and size-related changes in diet composition, which showed significant variations among size classes. Juvenile greater amberjack presumably feed on larger prey to meet their energy requirements.