Comparative growth and survival of two genetic strains of Atlantic cod (Gadus morhua L.) reared through the early life stages in a marine pond in western Norway
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The investigation was carried out in a marine pond in western Norway during spring and summer 1990. Two genetic defined strains of Atlantic cod (Gadus morhua L.) were used as broodstocks. A total of 11.1 x 10^6 cod larvae and eggs were released in the pond from 16 to 22 March. Approximately 80 % of the specimens were homozygous for the rare 30-allele at the PGI-1 locus (Strain-A), and the remaining were offspring from a farmed cod stock (Strain-B). Hydrographical parameters and feeding conditions of larval and juvenile cod were monitored. Gel electrophoresis of samples collected from the pond, revealed significant variation in the Strain-A/Strain-B frequencies with increasing age. The percentage of Strain-A dropped pronounced from the larval to the juvenile stage, and Strain-A had lower larval and juvenile growth rates than Strain-B, indicating size-dependent mortality during the pre-recruit period.