Final Report of the Working Group on the Integrated Assessments of the Norwegian Sea (WGINOR)

The third meeting of Working Group on Integrated Ecosystem Assessments for the Norwegian Sea (WGINOR) was held in Reykjavik, Iceland, 7–11 December 2015 and was chaired by Geir Huse (Norway) and Guðmundur J. Óskarsson (Iceland). The total number of participants was 15, representing Norway (8), Iceland (5) the Faroese (1), and Greenland (1). The objective of the meeting was to develop further and final-ize the work developed over the initial two meetings and represented by the ToRs.For the initial integrated assessment of Norwegian Sea (ToR a) it was decided to use a fairly straightforward three step operational approach consisting of: 1. Data assem-bly, 2. Data analysis, 3. Interpretation. Hence, relevant time-series of ecological, envi-ronmental, biological and fishery related variables were compiled, described and analysed (ToR b). The temperature of the Norwegian Sea is currently slightly above the normal and has had a downward trend in recent years after a peak in 2007. The biomass of mesozooplankton had a downward trend during 2003–2009, followed by an increasing trend in the subsequent period. In 2015, there was a reduction in the zooplankton level compared to 2014. The length-at-age of herring has been increasing in the last years and is negatively related to stock density. For mackerel on the other hand, there was a strong decreasing trend in length-at-age since 2007, in coherence with a strong density-dependent growth in the stock. A multivariate analysis was performed on all the time-series collected during the recent three years. The principal component analysis shows a shift in the first principal component from high values before 1995 and a sharp decline until 2010. The causes for these changes are not fully understood, but they are related to changes in the overall circulation. The work in WGINOR indicates that the Norwegian Sea ecosystem alternates between bottom up and top down forcing. Number of relevant publications in this field, both by WGINOR members and others, have appeared during the last three years and are addressed in the WGINOR report adequately.