Steingrund, P., Anker-Nilssen, T., Bjørnsson, H., Bogason, V., Broms, C., Danielsen, J., Hansen, E.S., Jacobsen, S., Johnsen, E., Olsen, H., Skagseth, Ø., and Hátún, H.
Abstract
The goal of this article is to evaluate the hypothesis that oceanographic features, i.e. the subpolar gyre (SPG) and the East Icelandic Current (EIC), cause an advection of nutrients and/or zooplanton onto the Icelandic, Faroe and Norwegian shelves that stimulate the abundance of forage fish, demersal fish recruitment and production of seabirds. We compared indices of SPG and EIC with zooplankton, forage fish (capelin Mallotus villosus, sandeels Ammodytes spp., herring Clupea harengus), recruitment of demersal fish (cod Gadus morhua, haddock Melanogrammus aeglefinus) and production of seabirds (Atlantic puffin Fratercula arctica, black-legged kittiwake Rissa tridactyla) on the three Nordic shelves where we concentrate on the 1970–2023 period with most data and focus on the area from Iceland, Faroe Islands and along the Norwegian shelf up to Lofoten Islands in Northern Norway. We found good support for our advection hypothesis, e.g., that a large SPG and/or strong EIC seemed to cause elevated levels of zooplankton, forage fish, demersal fish recruitment and seabird productivity on the three Nordic shelves. Importantly there was a prominent low-production period from 2003 to 2014 that could clearly been seen in most of the data series. Confounding factors, such as direct metabolic effects of temperature on zooplankton and forage fish or grazing of zooplankton by pelagic fish were not directly adressed, but could have played a role. Our study is of importance for ecosystem based management of marine fish and seabirds on the Nordic shelves. Future studies are suggested to fill in important knowledge gaps and quantify mechanistic links in trophic interactions.