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The spawning stock of Atlantic cod Gadus morhua in West Greenland waters was characterized by a drastic decline in the late 1960s and has since exhibited considerable variation. It has been suggested that the cod stock in West Greenland waters is composed of several stock components that include (1) a number of distinct local inshore populations spawning in separate fjord systems, (2) an offshore spawning component located on the fishing banks, and (3) a periodic Icelandic-East Greenland cod influx that mixes with the offshore and inshore West Greenland stock components. In an attempt to clarify the status of Atlantic cod in Greenland waters, we investigated the genetic structure at different inshore and offshore feeding grounds east and west of Greenland. A total of 1,581 genetic samples were collected within North Atlantic Fisheries Organization areas at inshore and offshore locations as well as within the International Council for the Exploration of the Sea area XIVb. Those samples were genotyped for 18 microsatellite loci and the pantophysin (Pan I) locus. Both types of genetic markers gave congruent results and suggest the presence of two distinct genetic components with limited connectivity in Greenland waters, namely, an inshore component and an offshore component. [ABSTRACT FROM AUTHOR]

The article presents a study which classifies the fingerprint of a harvest location of individual cod Gadus Morhua L. in the northeast Atlantic. The study used a combined approach to classification, such as otolith microchemistry, otolith shape analysis, and body morphometry, which found more powerful than any single technique. It also determined that based on binomial and multinomial logistic regression analyses, cod from widely separated origins were classified with high placement success. It noted that focusing on the placement of individual fish, the study represents a decisive advance toward identifying fish harvested from protected populations.

Most studies of the genetic structure of Atlantic cod have focused on small geographical scales. In the present study, the genetic structure of cod sampled on spawning grounds in the North Atlantic was examined using eight microsatellite loci and the Pan I locus. A total of 954 cod was collected from nine different regions: the Baltic Sea, the North Sea, the Celtic Sea, the Irish Sea and Icelandic waters during spring 2002 and spring 2003, from Norwegian waters and the Faroe Islands (North and West spawning grounds) in spring 2003, and from Canadian waters in 1998. Temporal stability among spawning grounds was observed in Icelandic waters and the Celtic Sea, and no significant difference was observed between the samples from the Baltic Sea and between the samples from Faroese waters. F-statistics showed significant differences between most populations and a pattern of isolation-by-distance was described with microsatellite loci. The Pan I locus revealed the presence of two genetically distinguishable basins, the North-west Atlantic composed of the Icelandic and Canadian samples and the North-east Atlantic composed of all other samples. Permutation of allele sizes at each microsatellite locus among allelic states supported a mutational component to the genetic differentiation, indicating a historical origin of the observed variation. Estimation of the time of divergence was approximately 3000 generations, which places the origin of current genetic pattern of cod in the North Atlantic in the late Weichselian (Wisconsinian period), at last glacial maximum. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 315–329. [ABSTRACT FROM AUTHOR]

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Nine out of 22 microsatellite primers tested were successfully amplified on three samples of cod Gadus morhua L. (two contemporary and one archived otolith samples). All loci were polymorphic (5–23 alleles/locus). The average observed heterozygosity across loci and samples was 0.625, ranging from 0.294 to 0.895 at each locus. All loci were under Hardy–Weinberg equilibrium, except PGmo56 that showed significant excess of heterozygotes in all studied samples. The isolated loci were suitable for degraded DNA and therefore useful for conducting a long-term temporal study with DNA obtained from archived otoliths of cod. [ABSTRACT FROM AUTHOR]

Abstract: Microsatellite DNA loci and the Pantophysin locus (Pan I) were used to investigate levels of genetic diversity within farmed strains of Atlantic cod Gadus morhua and to compare them with the wild source population. A total of 282 farmed samples originating from a spawning ground off the south-west coast of Iceland were sampled in the years 2002 and 2003, and 258 wild cod were collected at the same spawning ground in the same years. The farmed strains exhibited a lower mean number of alleles and allelic diversity than the wild samples at the microsatellite loci. Significant differences were observed between wild and farmed samples both in allele and genotype frequencies at the Pan I locus. We argue that the genetic divergence of wild and farmed samples of Atlantic cod may be due to a small number of effective founding breeders contributing to the genetic variation of the farmed strains, inducing a reduction in allelic diversity. We discuss the potential effect of breeding practices on the genetic diversity of Atlantic cod. [Copyright &y& Elsevier]