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Modern genetic methods make it possible to ‘travel back in time’ by running DNA tests on tiny remains of slime and blood on old samples from the archives. These boxes in the Greenland Institute of Natural Resources contain ear stones from cods. The ear stone is a tiny limestone structure in the cod’s head, which was originally collected because it features rings that can be used to determine the age of the fish. Analyses can now show how the cod populations were distributed in ages past and can therefore illustrate how fishing and climate change have affected the populations. The new results therefore played an important role in the recent decision by The International Council for the Exploration of the Seas (ICES) to recommend a 2013 fishing quota for cod in sheltered waters of 8,000 tonnes. Rapid test In order to establish the number of different cod populations, DTU Aqua biologists and the Greenland Institute of Natural Resources looked for differences in more than 1,000 different markers associated with genes affecting growth, sexual maturity and stress, Photo Line Reeh Greenlandic waters: three that spawn in Greenlandic coastal waters, and one Icelandic group that sometimes visits these waters, but probably does not spawn there. The reason for the interest in how many cod populations there are in the waters around Greenland is that this information is crucial to protecting the cod and ensuring sustainable administration of fish stocks. FISH GENE T IC S team is a global leader when it comes to developing genetic milestones and using them to understand population structures and local adaptations in fish. Sustainable fishing Thus far, on the basis of samples collected by the Greenland Institute of Natural Resources, biologists from DTU have proved that there are at least four distinct cod populations in Cod that spawned in the open sea near Greenland are under pressure. In contrast, cod spawned in coastal areas are thriving. But how can you tell the difference? Modern gene tests offer the solution to this problem. >> 38 Technical University of Denmark


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