| Summary: | Several polymorphic proteins have been used in studies of cod stock structure in northern Norway. Samples of Arctic cod spawning in Lofoten in the spring of 1981 were analysed for enzyme polymorphism by starch gel electrophoresis. The genotype distributions and allele frequencies estimated for spawning cod were consistent with corresponding results for eggs and yolksac larvae sampled in Lofoten and the Vesterålen area in May. Investigations of postlarvae in July, however, revealed samples which differed significantly from the samples of Arctic cod analysed earlier the same year. Most surprisingly, a postlarval sample from Eidsfjord, close to the main hatching area of Arctic cod in Vesterålen, differed in biological as well as genetic characters. Similar observations were made in 1982, when postlarvae were found in high numbers in the Vesterålen - Andfjord area. Samples of spawning cod were collected from several fjords in 1982. Especially, the sample drawn from Porsangerfjord differed from Arctic cod giving evidence for a genetically distinct stock of coastal cod in this area. This conclusion was also confirmed by analysis of postlarvae and juveniles found in the same area. Haemoglobin analysis in spring 1983 supported the existence of several genetically differentiated groups of coastal cod stocks in the area investigated.
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