Distribution and abundance of Norwegian spring-spawning herring during the spawning season in 2020 Toktrapport nr. 3-2020)

Sammendrag

During the period 14-26th of February 2020 the spawning grounds of Norwegian spring-spawning herring from Møre (62º20ˊN) to Nordvestbanken (70º40ˊN) were covered acoustically by the commercial vessels MS Eros, MS Kings Bay and MS Vendla. The survey was carried out under challenging weather conditions, however, the collected acoustic and biological data are considered to be of good quality. The estimated biomass was around 24 % lower and the estimated total number was about 10 % lower this year than in the 2019 survey. The uncertainty of the estimate in 2020 was estimated to be higher compared with 2019. The surveyed population was dominated by the 2013 and 2016 year classes. The 2016 year class is estimated to be around three times more abundant than the 2013 year class was as 4 year olds in 2017 (in this survey). The spatial distribution of the spawning stock was similar to earlier years; close to the coast south of Træna and on the slope around the banks outside Lofoten and Vesterålen, with the youngest and smallest herring in the north and older and larger herring in the south. The estimates of relative abundance from the survey in 2020 are recommended to be used in this year’s ICES stock assessment of Norwegian spring-spawning herring.