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.

调查期间使用Simrad ER60科学回声测深仪（scientific echosounder）获取了鲱鱼和蓝鳕丰度的声学估算值。将NASC值分配给鲱鱼、蓝鳕及其他声学目标的依据是拖网渔获物的组成和回声记录的特征。为估算丰度，将分配的NASC值在ICES方格（纬度0.5°×经度1°）内取平均值。对于每个统计方格，使用标准方程（Foote等，1987；Toresen等，1998）计算鱼类的单位面积密度（rA），单位为尾/平方海里（N*nm⁻²）。为估算鱼类总丰度，将每个统计方格的单位面积丰度乘以该方格的平方海里数，再对指定子区域内及整个区域内的所有统计方格求和。生物量估算通过将每个统计方格内的鱼类数量丰度乘以平均体重，再对指定子区域内及整个区域内的所有方格求和得出。挪威BEAM软件（Totland和Godø，2001）被用于估算总生物量。