Pelagic biomasses in the northern and southern Barents Sea for the period 1993-2013

Estimated pelagic biomasses (million tonnes wet weight) of pelagic fish stocks (capelin, herring, blue whiting, and polar cod) and 0-group fishes (cod, herring, haddock, polar cod, redfish, Greenland halibut, long rough dab, wolffish, blue whiting, and saithe) and macroplankton (mainly krill) in the northern and southern Barents Sea for the period 1993-2013. The background data were taken from [1]). Data for biomass calculation were collected during surveys: Trawl data for pelagic fish, 0-group fish, macroplankton were collected during a joint Norwegian-Russian 0-group fish trawl survey in August-September 1993-2003 using a small-meshed pelagic trawl (“Harstad”) with 20m*20m mouth opening [2]. Acoustic data for pelagic stocks (capelin, herring, blue whiting, and polar cod) were collected in September-October 1993-2003. Acoustic data are integrated continuously along the survey tracks, and mean values of acoustic back-scattering per nautical mile (nm) are recorded for mapping and calculations of fish biomass. The echo sounders are monitored continuously, and trawl hauls (“Harstad” trawl) are carried out whenever the recordings change their characteristics and/or the need for biological data makes it necessary [3]. Since 2004, both the 0-group trawl survey and the acoustic capelin survey have been part of a Barents Sea ecosystem survey (BESS, [4, 5]). The timing of the BESS allows access by research vessels to most of or the whole Barents Sea, sea-ice being at its seasonal minimum. In August-September, migratory species such as capelin have reached their maximum northern distribution at the end of the summer feeding period. At this time of year, the juvenile 0-group fish of commercially and ecologically important species are sufficiently large to be caught by trawl, while 0-group demersal species such as cod and haddock have not yet settled to the bottom. For further description of the sample processing, determination of biomass, and data series see [1].