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Differential survival up to harvest was evaluated for 73 communally reared families of Atlantic cod ( Gadus morhua ). Progeny from known family crosses were produced and mixed as fertilized eggs (2–3 families per incubator), newly hatched larvae, or as ~ 7 g juveniles to evaluate differences in contribution among families based on stage of mixing. All progeny were stocked into a single sea cage. Progeny were harvested and fin tissue collected at 991–1037 days post-fertilization ( n = 2001). A multiplex of six microsatellite markers was used to genotype broodstock and progeny for parentage assignment using PROBMAX. Of the progeny assigned ( n = 1996), only 34 were from 10 of the 27 families mixed as fertilized eggs. In contrast, all families mixed as hatched larvae or as ~ 7 g juveniles were represented (536 progeny from 11 of 11 families; 1426 progeny from 35 of 35 families, respectively). The differences in family survival were affected by sire and stage of mixing. The results indicate progeny should be combined as larvae or juveniles to reduce loss of genetic diversity in communally reared populations. Heritabilities for total body, carcass and fillet weight at time of harvest were ≥ 0.35 and suggest that the developing Canadian Atlantic cod aquaculture industry should benefit from genetic improvement of these traits. However, gonad weight was less heritable (0.11), indicating that sexual maturation will respond less favorably to traditional selective breeding methods. |
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