Effects of effective population size on the F2 growth and survival of bay scallop Argopecten irradians irradians(Lamarck)

In 2002, six cohorts ofbroodstock bay scallop Argopecten irradians irradians （Ne=1, 2, 10, 30, 50 and control） were randomly chosen from a population of bay scallop to produce offspring. After one year rearing, with the progeny matured, the similar experiment was done to produce the F2 generation. To determine the magnitude of Ne effects, the growth and survival rates in larvae and adult of six F2 groups were compared. Results showed that inbreeding depression existed not only in the Ne=1 group but also in the Ne=2 group. The growth and survival rates of the two groups were significantly lower than those of the other groups （Ne=10, 30, 50, control）, and there were no significant differences among the latter （P〉0.05）. At the same time, the amount of depression in the Ne=1 group was significantly higher than that of the Ne=2 group （P〈0.05）. These results indicated that the low effective population size （Ne）, which increases the possibility of inbreeding, could lead to some harmful effects on the offspring. So it is essential to maintain a high level of Ne in commercial seed production. Fta＇thermore, as the high fecundity of bay scallop might lead to increased inbreeding, selecting broodstock from different growout sites is recommended.

Effects of effective population size on the F2 growth and survival of bay scallop Argopecten irradians irradians(Lamarck)

In 2002, six cohorts of broodstock bay scallop Argopecten irradians irradians (Ne=1, 2, 10, 30, 50 and control) were randomly chosenfrom a population of bay scallop to produce offspring. After one year rearing, with the progeny matured, the similar experiment wasdone to produce the F2 generation. To determine the magnitude of Ne effects, the growth and survival rates in larvae and adult of six F2groups were compared. Results showed that inbreeding depression existed not only in the Ne=l group but also in the Ne=2 group. Thegrowth and survival rates of the two groups were significantly lower than those of the other groups (Ne=10, 30, 50, control), and therewere no significant differences among the latter (P>0.05). At the same time, the amount of depression in the Ne=1 group was signifi-cantly higher than that of the Ne=2 group (P<0.05). These results indicated that the low effective population size (Ne), which increasesthe possibility of inbreeding, could lead to some harmful effects on the offspring. So it is essential to maintain a high level of Ne incommercial seed production. Furthermore, as the high fecundity of bay scallop might lead to increased inbreeding, selecting brood-stock from different growout sites is recommended.