Geographic Variation in Atlantic Cod, Gadus morhua, off Eastern North America: A Biochemical Systematics Approach

Analysis of geographic variation in the frequencies of alleles at the Tf locus in Atlantic cod, Gadus morhua, indicates that it is possible to distinguish three major populations off eastern North America: (1) north of the Laurentian Channel, (2) south of the Laurentian Channel, and (3) Flemish Cap. The data also suggest that the north Laurentian stock may be further subdivided into a northern and southern component. The genetic distinction between the cod population on Flemish Cap and those on other areas of the continental shelf is confirmed by a significant difference in allele frequencies at the PGI-2 locus. It is suggested that the cod population on Flemish Cap may have persisted in isolation since the last glaciation. Key words: fish stock discrimination, transferrin, phosphoglucose isomerase, allele frequencies, genetic distance