Genotype distributions of cod from the Norwegian Skagerrak coast

The genotype distributions for cod, Gadus morhua L., from the southeastern coast of Norway are studied as part of a more extensive study on cod enhancement and the possible effects of mass liberation of 0-group cod on endemic cod populations. This paper focuses on possible geographical variation in allele frequencies, temporal variations in haemoglobin type frequencies and mean length of age of various genotypes. Twelve samples were analysed for genotype distribution of haemoglobins and the tissue enzymes LDH, PGI, IDH, PGM, and GPD by agar-gel and starch gel electrophoresis. Some intersample variations were found indicating heterogeneity of the total cod stock structure in the area. The haemoglobin-controlling genes occurred with similar frequencies in this material as in corresponding material analysed more than 25 years earlier. Possible associations between life history traits and individual genotypes were investigated, and genotype-dependent growth rate was indicated