As a part of the monitoring programs of the Japanese Antarctic Research Expedition (JARE), zooplankton sampling using a NORPAC (NORth PACific) standard net has been routinely carried out since JARE-14 (1972/73 season) to estimate the long-term trends of abundance, species composition and their temporal/spatial variation in the uppermost 150 m of the Indian Ocean sector of the Southern Ocean. Two separate monitoring surveys were completed during JARE-61 (December 2019 to March 2020). The icebreaker Shirase has a fixed schedule and route, traveling down longitude 110ºE each December and returning along 150ºE each March. Data collected on these fixed schedule seems to be ideal for long-term monitoring work in this region. We present data from its 2019/2020 voyage. In additions, separate samplings were carried out on board the T/V Umitaka-maru along 110ºE longitude in January 2020. This report provides the latest zooplankton data. These transect data can be used as time series and/or seasonal sets over the last 45 years.
A 2021 study studied this question.