Haemoglobin polymorphism in atlantic cod(Gadus morhua): Allele frequency variation between yearclasses in a Norwegian fjord stock

A total of 262 specimens (0-, and 1-group) of Atlantic cod(Gadus morhua) representing 4 different yearclasses were caught in Trondheimsfjorden, Norway, during 1977–1984. They were genotyped by agar gel electrophoresis for the polymorphic haemoglobin locusHbI (Sick, 1961). The analyses revealed a highly significant (P=0.0003) heterogeneity ofHbI allele frequencies between yearclasses. The difference in the frequency of theHbI-1 allele between the first (1977) and the last (1983) yearclass amounted to 0.18 (±0.07). The results appear to support recent reports on considerable selection effects atHbI, and stress the unreliability of allele frequencies at this locus for use in studies of the genetic population structure of cod.Contribution No. 229, Biological Station, N-7000 Trondheim, Norway