Unraveling the feeding strategies of the greater amberjack: insights into size-dependent dietary patterns and environmental influences in Taiwanese waters

The knowledge regarding the feeding ecology of the greater amberjack remains limited despite its ecological and economic importance. Therefore, this study investigated the feeding dynamics of the greater amberjack and its key prey species in Taiwanese waters. Samples were collected from the Taiwan Bank (22.5° N–24.5° N, 118.5° E–121.5° E) and Northern Taiwan waters (25° N–26° N, 121° E–123.5° E). Analysis of samples obtained between June 2020 and June 2022 indicates that environmental factors influenced the availability of prey species, thereby affecting dietary preferences. The prey-specific index of relative importance indicated that the predominant prey species were pelagic species (52.81%), followed by demersal species and unidentified teleosts (18.74% and 16.58%, respectively); squid and crustaceans were the least frequently consumed prey species (6.11% and 5.76%, respectively). Although no difference was discovered between males and females in terms of diet, seasonal and size-related variations were noted in the feeding patterns, as evident from the substantial ontogenetic shift observed in the dietary composition of the samples during the study period. The findings of this study improve the understanding of the feeding dynamics of the greater amberjack and the association between oceanographic factors, such as sea surface temperature (SST), sea surface salinity (SSS), sea surface height (SSH), mixed-layer depth (MLD), and eddy kinetic energy (EKE), and prey availability in the coastal waters of Taiwan.