Abstract：Two shell type strains “wide‐shell” and “plate‐shell” of Manila clam ( Ruditapes philippenarum) were established using Zhangzi island populations .In this experiment ,the shell length , shell width ,shell height ,live body weight ,tissue weight and fecundity were compared between these two strains .The growth and survival of the offsprings were studied .The results showed that the wide‐shell strain had significant higher shell length ,live body weight and tissue weight than plate‐shell strain did (P<0 .05) .The shell width which had the maximal direct effect was the key effective factor on live body weight for both strains .The shell length which had the maximal direct effect was the key effective facter on body‐tissue weight for both strains .No significant difference was observed in D‐larvae at days 0 ,3 and 6 between the two strains (P> 0 .05) ,but plate‐shell strain had larger shell length than the wide‐shell strain did (P<0 .05) at 15 days .At juvenile stage ,the shell length of wide‐shell strain was larger than the plate‐shell strain (P<0 .05) except at 30 days .The wide‐shell strain had higher survival than the plate‐shell strain at larval and juvenile stages (P<0 .05) .
