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%) was 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 whiting 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.
- Assessments of the benthos biomass in 2017 were very high but this most likely related with overestimation of the biomass due to the technical causes during the benthic monitoring like in 2012. The distribution area of the invasive snow crab was larger than in previous years, and for the first time recorded northeast of Svalbard. The shrimp, Pandalus borealis, population was within the long-term mean and stable.
- The summer abundance of minke whales in the Barents Sea is now about 50 000 animals and has been quite stable or increasing over the period. The sighting rate from the 2017 survey is the highest recorded which may confirm the apparent increasing trend at present. In 2017, 1518 individuals of nine species of marine mammals were observed during the BESS, August-October 2017 and an additional 46 individuals were not identified to species level.
- A large-scale monitoring of marine litter performed in the joint Norwegian–Russian ecosystem monitoring surveys in the period from 2010 to 2017.
- During the time-series, plastic dominated number of observations with marine litter, as 72% of surface observations, 94% of pelagic trawls, and 86% of bottom trawls contained plastic. In 2017, marine litter on the surface (floating) and taken by trawls dominated by plastic. Wood was registered in the 28.4% of stations, while textile, paper, rubber and metal was observed occasionally.
