Ecosystem based management of sandeels, demersal fish and seabirds in Boreal ecosystems in Northeast Atlantic

Ecosystem based management has been a hot topic for decades and the current project aims to explore the potential of this approach on the marine shelves at Iceland, Faroe Islands and Norway, here termed boreal ecosystems in Northeast Atlantic. Ecosystem based management implies that the ecosystem function is adressed with all its variables and complex relationships. In order to reduce complexity the project focused on sandeels, demersal fish and seabirds, thus putting emphasis on the food chain from phytoplankton, zooplankton, sandeels to demersal fish and seabirds. In the work of the project it soon became clear that there were other food chains available, for example that seabirds could prey on krill, which is seen for the particular puffin to the left in the cover picture. It was noted that the relationships between oceanography/zooplankton and seabirds were as strong as relationships between forage fish and seabirds and one main reason being that seabirds could switch their preference between forage fish or even to switch to crustaceans (krill) and this issue was dealt with by broadening the focus to include fish larvae of different fish species. In the project it was noted that the strongest declines in seabird numbers were found in the shelf area from south Iceland, Faroe Islands to the Norwegian shelf up to Lofoten. This is the area where sandeels comprise an important forage fish and where other forage fish like capelin are less frequent. This area was thus chosen as the study area in the project. It was also noted that oceanographich features like the size of the subpolar gyre or the strength of the East Icelandic Current (EIC) were of great importance to demersal fish and seabirds. However, to link the ecosystem function to fisheries it was necessary to find an ecosystem component that was susceptible to fishing and the choice fell on fish larval survival. Fish larvae represent a fragile ecosystem component that is highly vulnerable to predation and that has direct links to the size of the demersal fish stocks as well as the amount of food for seabirds. The predators on fish larvae were found to be pelagic fish such as herring and mackerel, but also Norway pout was considered, although it was noted that there are other predators on fish larvae that could not be taken into account. A main finding, which probably is novel, was that the abundance of demersal fish could hamper the predatory effect of pelagic fish on fish larvae, for example by scaring pelagic fish away from the shelves or areas where the fish larvae are found. The effect of demersal fish on the survival of fish larvae seemed to be less than the effect of oceanographic variables or primary production, but, nevertheless, seemed to hold a potential that should be further studied in the future. The report is structured as separate sections: bottom-up introduction, seabird productivity in the eastern Norwegian Sea, puffin productivity in South Iceland, seabird productivity on the Faroe Islands, and finally fish larvae dynamics and predation by pelagic fish.