This study describes the complete diallel hybridization between newly introduced bay scallop stock(W) from Canada and local commercial stock(D) grown under laboratory conditions, in China. Larval survival and growth during all life stages(larvae, spat, and adult) were compared among hybrid(DW, WD) and purebred(DD, WW) populations. Signifi cant heterosis was detected for survival during the larval stage(>1% of the mid-parent values). The mean heterosis( H m) varied in growth throughout the life span. More than 50% of the H m values were positive and negative in the DW and WD groups, respectively. The infl uence of maternal effects and mating types(intrapopulation vs. interpopulation crosses) on growth for all life stages was not consistent. Larval survival did not differ signifi cantly( P >0.05) with maternal effect or mating type. In the harvest stage, shell length(SL), shell height(SH), shell width(SW), and total weight(TW) were larger in the hybrid compared with the inbred groups. Positive H m values were observed in SL(1.5%), SW(5.8%), and TW(12.3%), and were more signifi cant in the DW groups(6.1%, 4.5%, 6.8%, and 27.2%). These results suggest that hybridization between two geographic populations is a good tool for improving bay scallop growth. However, unstable heterosis between the two populations requires further study.
