This study explored whether the growth and sexual maturity of female John Dory (Zeus faber) differed in relation to hydrographic conditions at sample sites in the East China Sea. John Dory were collected around the margin of the continental shelf from the north-east to south-west waters of the East China Sea, and seasonal changes in spatial distribution were unclear. These probably reflected physiological constraints on salinity, as John Dory are distributed only in waters of high salinity. Thermal gradients along latitudinal lines were evident within sample sites. The northern population was subject to lower temperatures than the southern population during all sampling periods. There were no significant differences in length–age relationships between sampling locations, although the northern population had better body condition than their southern counterparts for a given length. However, northern John Dory matured earlier than their southern counterparts with the same relative condition factor.