A revised biomass estimation of Antarctic krill based on the up-to-date swarm based method for CCAMLR Division 58.4.1 in 2018/19 using data obtained by Japanese survey vessel, Kaiyo-maru

A multidisciplinary ecosystem survey in the eastern Indian sector of the Antarctic (CCAMLR Division 58.4.1) with a focus on Antarctic krill was carried out by Japanese survey vessel, Kaiyo-maru, during the 2018/19 season. A revised biomass (B₀) of Antarctic krill was estimated using the survey data applying Echoview template, EchoviewR and R code for the random sampling theory estimator which were adopted at SG-ASAM-19. The revised B₀ was estimated as 4.325 million ton (CV=17.0 %) based on the up-to-date swam based method. The point estimate was comparable with the estimate in 1996 by BROKE (4.83 million ton with CV=17 %). However, they can not be compared directly because (1) biomass estimation methods were different, (2) timing of the surveys were different (Kaiyo-maru survey commenced about 40 days earlier than BROKE) and (3) areal coverages were different primary because of difference of positions of sea ice edge especially in the western part of the Division.