The major trends in fish distribution and abundance in the NwS during the last ten years have been the expansion and increase in the mackerel stock since 2007 and the decline in the NSS herring stock after 2009.
The mackerel stock was at a stable low level at the beginning of the 1990s. It started to increase in the mid-2000s and is currently at its maximum recorded level (Figure 12). A westward and northward expansion of its summer feeding grounds outside of NwS also started in the mid-2000s; whether this was a consequence of increasing stock, higher sea temperature in those areas, or less feeding opportunities in NwS remains to be answered.
The NSS herring has been declining since 2009 and is now considered to be at the precautionary level biomass of 5 million tonnes. The herring are getting older and a new strong cohort is needed to sustain the breeding stock.
The blue whiting stock, which prefers the slope areas of the Norwegian Sea and adjacent waters for feeding both as juveniles and adults, was at its maximum recorded level in the mid-2000s. A decrease followed until around 2011, when the stock size started to increase again as strong year classes entered the stock.
The beaked redfish stock has recovered from the low level it sustained some years ago, while the current golden redfish stock size is record low.
The stock size of saithe is increasing, with saithe mainly found along and off the coast in the NwS.
Figure 12: Biomass (SSB to BMSY trigger ratio) for Northeast Atlantic mackerel (Mac-nea), Norwegian spring-spawning herring (Her-noss), and blue whiting (WHB-comb), based on ICES 2016 assessments.