Changing fish communities in Arctic Coasts: The role of climate change and climate variability on the distribution of Atlantic cod (Gadus morhua)

In recent years, several studies postulate a significant increase in the transport of warm Atlantic water masses towards Svalbard driven by climate change. A consequence of this Arctic “Atlantification” seems to be a higher abundance of Gadus morhua (Atlantic cod) in these areas. Similar increases in cod stocks were reported between the 1920s and 1960s, a period known as Early Arctic Warming. As a major competitor for food and habitat resources, an increase in the overall abundance of G. morhua in the Arctic will have considerable consequences for the ecosystem. The native cod stock of Boreogadus saida (polar cod) is most susceptible to these changes in the area. In this study, we hypothesis that G. morhua has established a local “non-migratory” spawning stock at Svalbard, similar to a local coastal cod stock in Norway. We specifically focus on two questions: 1) Is there a correlation between the overall abundance and distribution patterns of Atlantic cod stocks at the coast of Svalbard with longer-term temperature patterns? Is there an increase in the overall abundance of Gadus morhua during periods when warmer water surround Svalbard? 2) Is the Atlantic cod stock on the west coast of Svalbard genetically / morphologically distinguishable from that of the Norwegian coast, where the migratory origin of Gadus morhua is assumed? And if so, can this stock establish as a local spawning stock? In the framework of a cooperative sampling programme from 2018 to 2020, together with Norwegian and AWI colleagues, genetic analysis at individual and population level will be conducted. Together with catch data modelling approaches, we aim to improve our knowledge on possible future distribution patterns of Atlantic cod migrating towards Arctic waters and their effects on the local Arctic community