The Northeast Atlantic Mackerel supports one of the most valuable European fisheries producing up to 700000 tonnes per year. Historically the Northeast Atlantic mackerel stock has been split into three spawning components, a western, a southern and a Nort h Sea component. Prior studies have demonstrated strong indications of genetic differences in the three spawning components.The main objective of the present study is to develop a set of genetic markers that can describe within- and between genetic vari ation for the three components and test if this set can be used as a method to identify these components in samples from commercial catches. The present study represents a pilot study with focus on the development of two sets of genetic markers, micro satellites and SNPs. A robust and powerful set of 50 microsatellites and 150 SNPs will be developed. Initial analysis will be performed using the developed markers for the purpose of describing genetic variation within and between spawning areas, as well as in commercial catches. Samples are already collected from the western and the southern spawning component. Samples from spawning mackerel from the North sea component will be collected both in 2007 and also in the spring of 2008.In the planned main pr oject (applied for next year) three institutions with wide experience in marine/aquaculture research, The Institute of Marine Research(IMR), The Norwegian School of Veterinary Science(NVH) and National Institute of Nutrition and Seafood research (NIFES) w ill collaborate in a consortium. IMR will have the responsibility for collection of samples in a broad international collaboration (most of the samles are already collected), NVH will have the responsibility for development of genetic markers and most gen etic analysis and NIFES will have the main responsibility for parasite analysis.The collaborators will benefit mutually from the broad competence in the group and increase likelyhood of success of the project.