Oriental bonito (Sarda orientalis) migrate to the the bay of Yilan to spawn from winter to spring every year. During the spawning season, S. orientalis are more delectable as they are plumper. However, little is known about its early life. Each S. orientalis egg is a sphere with a diameter of approximately 1.3 mm, exhibiting pelagic and isolated characteristics. It is the only economically significant pelagic fish species in Taiwan whose eggs are enriched with oil globules. In this study, 118 eggs were collected from the key spawning area (the bay of Yilan) off northeastern Taiwan during March 2022. Of the 38 sampling stations, 16 had S. orientalis eggs, and the highest density of eggs was recorded in the waters off Nan’ao. We report that the presence or absence of S. orientalis eggs is closely linked to a combination of waters 4 m deep with mean salinity larger than 34.2 psu and waters 10 m deep with mean chlorophyll-a concentration of less than 1 µg/L. The relationships between the ichthyoplankton and the zooplankton abundance observed in our research exhibit a positive pattern. Our findings provide the first report on the response of S. orientalis eggs distribution to the specific hydrological variables in Taiwan, offering insights for future stock management and sustainability of S. orientalis.