We evaluated the effect of selection for one or two traits on the adductor weight of the bay scallop, population that had been produced by continuous progeny selection. We tested the effect of selection for shell height (selection pressure =10%) and/or body weight (selection pressure =1%). There was no significant difference(>0.05) in spawning, fertilization rates, hatching rates, the growth rate of larvae, the survival to the mid-cultivation period, and the morphology of adults between the positive selection group, negative selection group, and control group. However, there was a significant effect (<0.05) on the survival rate of juveniles. The survival during the grow-out period, the body weight of adults, and the values for each of the traits in the positive selection group were highest in the positive selection group and lowest in the negative selection group. We observed high realized heritability in both the positive and negative selection group, though the value was higher for the positive selection group than the negative. The inheritance of body weight and adductor weight was higher when both traits were selected than a single trait. Our results suggest there is a genetic correlation among shell height, body weight, and adductor weight, such that selection for the two former traits will affect the adductor weight. Concurrent selection for the two traits appears to have an additive effect, which will likely increase the rate of selection for adductor weight and thereby increase the yield. Our results provide a theoretical basis for improved selective breeding of the scallop.