Publication Abstract

Historical diets, food web dynamics and climate change in the Arctic

Bryony L. Townhill and John K. Pinnegar

Atlantic cod Gadus morhua stocks in the Barents Sea are currently at levels not seen since the 1950s, however it is unclear how these very high population numbers can be supported in terms of prey availability and whether or not high cod numbers will have consequences for other important commercial fish such as herring and capelin. Initial analysis of historical stomach data in the region has shown that cod diets have varied considerably over recent decades and even year-on-year, with the importance of fish prey varying between years. In collaboration with the University of Oslo, Cefas has carried out detailed analysis and modelling using a set of biological and hydrographic datasets for the Bear Island (Spitsbergen) region between the 1930s and 1970s. These data have been compared with more recent datasets collected by Norwegian and Russian scientists for the purposes of multispecies fisheries modelling. Developing an understanding of historical food web dynamics, and in particular relationships between climatic conditions and diet, can enable predictions of how future changes might impact fisheries. This study has placed changes in cod diet in a long-term context of both warming and cooling periods, changes in fishing mortality as well as changes in the availability of particular prey organisms (euphausids, hyperiid amphipods, capelin, herring). As the Arctic is highly sensitive to climate change, but is also fished by many nations, the results of this project are directly relevant to future management of cod stocks.