Pelagic fishes migrate throughout their life history stages and migration plays an important role. Climate change influences the marine environment and the increase of zooplankton’s abundance. The variations affect the food web structure of pelagic fish by trophic cascade to understand their movement behavior and life history. However, pelagic fishes migrate worldwide, and it is difficult to track their movement behavior. The sunfish migrates throughout the Pacific Ocean, regarded as a suitable target for exploring the trophodynamics of food web structures. Taiwan, located in the western Pacific Ocean, is an oligotrophic area and a migrate pathway of pelagic fish for feeding and spawning. Previous studies indicated that sunfish migrated northward to Japan. Thus, the aim of this study is to examine the spatiotemporal trophic dynamics of sunfish by using SIA (δ13C and δ15N) and associated statistical frameworks for SIA data (e.g., Bayesian mixing models). Our study will quantify the relative contribution of various prey types to sunfish diet, and explore relationships between trophic dynamics and environmental variables to more fully understand and predict the influence of ecosystem variability, climate change, and fishing pressure on spatiotemporal distributions and trophic dynamics of sunfish in the North Pacific Ocean.