Update of analysis on sea-ice concentration of southern part of 48.6 and 58.4.2 for the new research block on expected spawning ground of TOA

Following WG-SAM-16/42 Rev. 1, we updated the analysis on the sea-ice concentration of the period (2002-2017 until April) for 48.6_4 and 48.6_5. In addition, we also analyze the ice concentration of 58.4.2 to examine accessibility there for fishing vessels as candidate for a new research block. This research block is hypothesized as one of spawning grounds for TOA by Taki (WG-FSA-16/32 Rev. 1) and hence it should be covered by research for stock assessment in the near future.