The present book summarizes parts of the research made in the Norwegian Multispecies program. This program was initiated by the then Norwegian Council of Fisheries Research, which was later integrated in The Research Council of Norway. Modelling has been a key element in the program. In the first place, modelling, be it singlespecies or multispecies modelling, is an efficient way of summing up existing knowledge, and performing analyses of different types on the basis of it. Further- more, models may serve as a meeting ground between fishery researchers from differ- ent academic fields. This has been an important aspect of the Multispecies program, bringing together oceanographers, biologists, economists, mathematicians and stat- isticians in fruitful cooperation. That this has proved possible may be taken as an important result of the program. The multispecies aspect has perhaps underscored the need for inter-disciplinary cooperation. The different authors are, of course, responsible for their respective contributions. Technical assistance in preparing the manuscript has been given by Knut Arrestad and Ian Knutsen, both at the University of Bergen. Bergen, October 1997.