Stock assessment of marine Crustecea suffers from uncertainties in estimation of size and yield due to difficulties in identifying population entities. This project will use molecular methods to investigate weather Antarctic Krill (Euphausia superba) in the Southern Ocean and northern shrimp (Pandalus borealis/ P. eous) in the north Atlantic and north Pacific should be viewed as large panmictic populations or if they ought to be subdivided in sub-populations on genetic grounds. Yearly landings of northern shrimp reach ˜ 250 000 metric tonnes, and ˜ 100 000 metric tonnes of Antarctic Krill are landed per year. In January 2000 I collected krill samples from 12 stations in an area from east of S. Georgia via the S. Orkney Islands to SW of the S. Shetland Islands. Samples of P.borealis from west Greenland, the Gulf of St. Lawrence, the Gulf of Maine, Icelandic waters, the Barents Sea, the Norwegian coast and the North Sea and Skagerrak in the Atlantic have been obtained or are being obtained. For comparisons I will also get samples from the coast of Alaska and the Berings Sea. In addition to extracting amplifying and sequencing DNA from the 16 S gene and COI gene we (co-operation with Dr. P. Sundberg, Mrs S. Viker and Mrs. A Hjelmgren, Zoology Dept. Göteborg University) will attempt to design primers for more fast-evolving genes, which we assume will be better suited for our analyses. In order to design primers that covers these sections we will endeavour to sequence the entire mitochondrial genome for the model species. Results will be analysed in co-operation with Dr. Ziad Thaib, Applied Mathematics Chalmers School of Technology and Göteborg University.