Regional variability in the trophic requirements of shelf sea fisheries in the Northeast Atlantic, 1973-2000

Hydrographic, plankton, benthos, fisheries landings, and fish diet data from shelf sea areas in the Northeast Atlantic have been combined into an analysis of the foodweb structure and secondary production requirements of regional fisheries. Fish landings from the Baltic and North Sea are shown to be taken from a lower trophic level and are shown to be overall more planktivorous than those from shelf edge regions. The secondary production required per unit of landed fish from the North Sea was approximately half that for landings from the southwest approaches to the UK, referred to as the Celtic Seas, where zooplankton production accounted for only a small fraction of the secondary production demands of the fisheries. In the North Sea, variability in zooplankton production seems to have exerted a bottom-up effect on fish production, which in turn has exerted a top-down effect on the benthos. Conversely, Celtic Seas benthos production has been a bottom-up driver of fish production, which seems to have been independent of variability in plankton production.Thus, climate and fishing pressures can be expected to influence these regional fisheries in very different ways. Overall, the results indicate very strong spatial patterns in the fish foodweb structure and function, which will be important considerations in the establishment of regional management plans for fisheries.