The aim of this study is twofold: to provide a theoreti­ cal and an applied analysis of multispecies fisheries. The theoretical part will include concepts and analysis which, hopefully, will be of interest not only to economists, but also to biologists and ecologists. The application of the theoreti­ cal model and analysis to the Barents Sea fisheries gives empiri­ cal content to the analysis, which is important for the advance­ ment of fisheries management science. It is also my firm belief that this kind of work in the end will be beneficial to the people trying to make a living from harvesting marine resources. For thousands of years man has been whaling, sealing and fishing in these cold and harsh surroundings. The relative importance of the different species in the ecosystem has changed throughout history. In the seventeenth century the abundant, slow-swimming Greenland right whale and the Biscayan right whale in the Barents Sea area were so valuable, especially to English and Dutch whalers, that the intensive exploitation of these common property resources probably were the main reason for the extinction of these two stocks. The two species are, however, still present in other parts of the North Atlantic Ocean. Except for these two stocks of whales there is no knowledge of other stocks of sea mammals or fish in this area being extinct in historical time.