| Résumé | For many aquaculture finfish species, the current broodstock have been collected from the wild or have undergone only a few generations of domestication. The Atlantic halibut (Hippoglossus hippoglossus) aquaculture industry in Atlantic Canada has retained F1 juveniles (n = 145) from the 1996 spawning of wild adults for candidate broodstock. Through the development and use of a five-microsatellite DNA marker multiplex, we determined the parentage of these 1996 F1 individuals, which are being reared at one government and two industry hatcheries, and evaluated the change in genetic variation between the wild and the 1996 F1 stock. In the three groups of F1 fish, single parental pairs were assigned to 98%, 96% and 100% of individuals. Large full- and half-sibling groups were identified within and across F1 groups and, overall, only 36% of attempted crosses were represented in the retained fish. Effective population size in the parental group decreased from 27 to 13 when variance in family size was accounted for and to 12.5 when changes in gene diversity (compared to the combined F1 stocks) were considered. Statistically significant differences in measures of genetic variation were not widely observed between groups (original wild sample, parental group, three F1 groups and combined F1). However, the F1 population shows a 26% decrease in total allele numbers compared to the wild sample. These observations demonstrate the utility of genetic tools in the evaluation of genetic diversity and determination of pedigree during the establishment of new broodstock. They also emphasize the necessity for closely monitoring future matings among these fish and suggest the need to introduce additional genetic variation into this group of Atlantic halibut broodstock. |
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