Interim Report of the Working Group on the Integrated Assessments of the Barents Sea (WGIBAR), including Annex 5: the state and trends of the Barents Sea ecosystem in 2017

The Working Group Report of the Working Group on the Integrated Assessments of the Barents Sea (WGIBAR), chaired by Elena Eriksen (Norway) and Anatoly Filin (Russia), met in Tromsø, Norway, on 9–12 March 2018. The meeting was attended by 21 participants from 4 institutes and 2 countries. The group updated most of the time-series data and established additional time-series for the oceanographic conditions (currents, temperature, and salinity (1980–2017), me-so zooplankton (1989–2017) and 0-group fish (six fish species, 1980–2017), based on WGIBAR-subareas for the Barents Sea. The group discussed the 2017 state and changes of the Barents Sea ecosystem (see short summery below). The group discussed also different ecosystem models and their use in the IEA, and the group will be a platform for evaluation, testing, and development of ecosystem models. WGIBAR working group provide knowledge of the status, changes, relationships, and processes in the ecosystems to the Joint Russian-Norwegian Fisheries Commission, the Joint Russian-Norwegian Environmental Commission, the Norwegian Ministry of Climate and Environment and different ICES working groups.Since the 1980s, the Barents Sea has gone from a situation with high fishing pressure, cold conditions and low demersal fish stock levels, to the current situation with high levels of demersal fish stocks, reduced fishing pressure and warm conditions. The cur-rent situation is unprecedented, and the Barents Sea appears to be changing rapidly. The main points for 2017 are:• The air and water temperatures remained higher than average and typical of warm years, yet lower than temperature in 2016. In autumn, the area covered by Atlantic waters (>3°С) was large than in 2016; areas covered by Arctic and cold bottom waters (<0°С) were small but larger than in 2016. Ice coverage was much lower than normal, but higher than in 2016; the lowest value (1%) observed in September.• Spatially integrated net primary production has increased over the years. A noteworthy increase is observed in the eastern regions where sea ice cover-age has diminished over the years. An increase in ice-free areas, and length of the growing season, provide improved habitat for phytoplankton growth.• Mesozooplankton biomass during autumn was higher than in autumn 2016 in the eastern Barents Sea and on the Central Bank, but lower on the Great Bank. Zooplankton biomasses in the Central Bank and Great Bank subareas have shown declining trends since the peak in 1995. An increasing trend in krill biomass has been observed during the last decades – and the level in 2017 was above the long-term average. Amphipods are still considered to be at a low level - although some large catches were made north and east of Svalbard. Jellyfish biomass was at third highest level since 1980.• The capelin stock has recovered after a mini-collapse in 2015–2016, and the biomass of young herring is the highest since 2005. Polar cod and blue whit-ing biomass is low. Cod and haddock biomass have decreased in recent years following a peak around 2013, but is still above the long-term mean. The 2016 and 2017 year classes of haddock seem strong and could be of the same order of magnitude as the strong 2004–2006 year classes. Sebastes mentella, Green-land halibut and long rough dab biomass is stable at or above the long-term mean.