The large yellow croaker (Larimichthys crocea) is the most important mariculture fish species in China and the wild stocks of this croaker have collapsed in the past decades due to high fishing pressure and habitat degradation. Due to a lack of wild croaker samples, however, studies concerning the genetic changes of the cultured croaker stocks compared to their wild counterparts were never conducted. Here, we collected three wild populations in the northern and central East China Sea during fisheries survey and investigated the differences in terms of genetic diversity and differentiation between and within cultured stocks and wild populations. Our results demonstrated that the cultured croaker had significantly reduced genetic diversity in contrast to the wild populations, and also presented statistically significant differentiation from the wild, indicating that enhancement of the current wild stock should be conducted with caution. These changes may be caused by founder effects, artificial selection and random genetic drift. With a relatively high level of genetic diversity, the wild populations showed important value for improving the ongoing breeding program of this croaker. Further, we detected no differentiation among the wild populations, suggesting that the wild croaker in the northern and central East China Sea should be considered as one unit for management and conservation.