Can changes in the fisheries yield in the Kattegat (1950-1992) be linked to changes in primary production?

The increase in fisheries yield in the Kattegat during the last four decades can be correlated with a concomitant increase in annual primary production in the region However, this correlation does not necessarily indicate cause and effect. Other changes have occurred during this period that may also affect fisheries yield (changes in fishing effort. market demand, fleet composition, etc.). This paper examines some of these factors in an effort to identify the underlying cause(s) of the observed increase in fisheries yield. It is concluded that, although there have been major changes in the structure of the fishing fleet and fishing effort in the Kattegat during this period, the observed increase in fisheries yield probably reflects, at least in part, a real increase in fish biomass. It is not possible to document a direct link between this suspected increase in biomass and an increase in primary production. It is, however, noted that the changes in the relative proportion of benthic to pelagic species in the fishery are consistent with the changes which are predicted to occur following an increase in primary production. (C) 1996 International Council for the Exploration of the Sea