In the case of the Atlantic cod, Gadus morhua, the controversy arises from the ambiguous results provided by different types of genetic markers. Highly significant differences have been observed between Baltic and North Sea populations and between Norwegian coastal and arctic stocks at blood protein loci such as hemoglobin1 (Hbl) and transferrin (Tj) (FRYDENBERG et al. 1965; SICK 1965; MOLLER 1968; DAHLE and JORSTAD 1993), but not among populations sampled throughout the entire species' range and scored for a larger set of routine electrophoretic loci (MOM et al. 1985)