Spatially explicit estimates of length and biomass of Clupea harengus (Norwegian spring spawning herring) from acoustic and trawl surveys in the North-East Atlantic in May 2012

Acoustic estimates of herring and blue whiting abundance were obtained during the surveys using the Simrad ER60 scientific echosounder. The allocation of NASC-values to herring, blue whiting and other acoustic targets were based on the composition of the trawl catches and the appearance of echo recordings. To estimate the abundance, the allocated NASC -values were averaged for ICES-squares (0.5° latitude by 1° longitude). For each statistical square, the unit area density of fish (rA) in number per square nautical mile (N*nm-2) was calculated using standard equations (Foote et al., 1987; Toresen et al., 1998). To estimate the total abundance of fish, the unit area abundance for each statistical square was multiplied by the number of square nautical miles in each statistical square and then summed for all the statistical squares within defined subareas and over the total area. Biomass estimation was calculated by multiplying abundance in numbers by the average weight of the fish in each statistical square then summing all squares within defined subareas and over the total area. The Norwegian BEAM soft-ware (Totland and Godø 2001) was used to make estimates of total biomass.

Spatially explicit estimates of length and biomass of Micromesistius poutassou (Blue Whiting) from acoustic and trawl surveys in the North-East Atlantic in May 2004

Acoustic estimates of herring and blue whiting abundance were obtained during the surveys using the Simrad ER60 scientific echosounder. The allocation of NASC-values to herring, blue whiting and other acoustic targets were based on the composition of the trawl catches and the appearance of echo recordings. To estimate the abundance, the allocated NASC -values were averaged for ICES-squares (0.5° latitude by 1° longitude). For each statistical square, the unit area density of fish (rA) in number per square nautical mile (N*nm-2) was calculated using standard equations (Foote et al., 1987; Toresen et al., 1998). To estimate the total abundance of fish, the unit area abundance for each statistical square was multiplied by the number of square nautical miles in each statistical square and then summed for all the statistical squares within defined subareas and over the total area. Biomass estimation was calculated by multiplying abundance in numbers by the average weight of the fish in each statistical square then summing all squares within defined subareas and over the total area. The Norwegian BEAM soft-ware (Totland and Godø 2001) was used to make estimates of total biomass.

Total phytoplankton abundance and biomass in the surface and fluorescence maximum layers and contributions of dominant species to their values in the Werstern Arctic in July-August 2003

Phytoplankton community was studied in the Bering Strait and over the shelf, continental slope, and deep-water zones of the Chukchi and Beaufort Seas in the middle of the vegetative season (July-August 2003). Its structure was analyzed in relation to ice conditions and seasonal patterns of water warming, stratification, and nutrient concentrations. Overall variations in phytoplankton abundance from 200 to 6000000 cells/l and biomass from 0.1 to 444.1 µg C/l.were estimated. The bulk of phytoplankton cells concentrated in the seasonal picnocline at depths 10-25 m. The highest values of cell abundance and biomass were recorded in regions influenced by inflow of Bering Sea waters or characterized by intense hydrodynamics, such as the Bering Strait, Barrow Canyon, and the outer shelf and slope of the Chukchi Sea. In the middle of the vegetative season, phytoplankton in the study region of the Western Arctic proved to comprise three successional (seasonal) assemblages: early spring, late spring, and summer assemblages. Their spatial distribution was dependent mainly on local features of hydrological and nutrient regimes rather than on general latitudinal trends of seasonal succession characteristic of arctic ecosystems.