Haemoglobin frequencies and vertebral numbers of cod (Gadus morhua L.) off northern Norway - test of a population structure hypothesis

Cod (Gadus morhua L.) off northern Norway are divided into two main groups. The north-east Arctic cod (NAC) migrate southwards from the Barents Sea to the main spawning area near the Lofoten Islands on the coast of northern Norway. Eggs and larvae are carried northwards along the coast into the Barents Sea by the Norwegian Coastal Current. Coastal cod (CC) are present along the entire Norwegian coast and are relatively stationary. Cod were sampled in deep and shallow waters at 11 localities in northern Norway south of Lofoten. The results show haemoglobin-allele frequencies and vertebral numbers that are typical for coastal cod. The variation in haemoglobin-allele frequencies between samples was relatively small in this study, compared with similar studies from north of Lofoten. These results indicate a less heterogeneous cod population structure to the south compared with the north of the Lofoten Islands. This conforms to the hypothesis that some NAC settle along the coast and in the fjords of northern Norway north of Lofoten.