Argopecten irradians concentricus has been cultivated along the southern coast of China for about 16 generations since its first introduction in 1991. To determine the effects of self-fertilization on the production traits of this isolated bay scallop population, 12 self-fertilized families and a mass-spawned group were produced and studied. The hatching success and survival at larvae, juvenile, and adult stages of the offspring of the mass-mated group were all significantly greater than that of 10 of the 12 self-fertilized families examined, and not significantly different from that of other 2 self-fertilized families. For newly hatched larvae on day 1, no significant difference in size was found among the self-fertilized families and the mass-spawned group. The shell length of the mass-mated group on days 9, 30, 75 and 230, and the live weight on days 75 and 230 were always significantly larger than that of 9 of the 12 self-fertilized families, and not significantly different from that of the other 3 self-fertilized families. In addition, a significant difference in survival, shell length, and live weight was seen among the 12 self-fertilized families at all development stages. The current study demonstrated the occurrence of inbreeding depression for production traits in the closed population of A. irradians concentricus and the necessity of avoiding inbreeding when creating a breeding production, although not all families are significantly affected by inbreeding.