Zooplankton was collected at 34 stations in the Chaun Bay, an enclosed bay of the East Siberian Sea (Arctic Ocean), during the 60th cruise of the RV "Akademik Oparin". Sampling was conducted between 9 and 21 October 2020 by Daria A. Yurikova, Glafira Kolbasova, and Vitaly L. Syomin (IORAS). Up to two depth layers were sampled vertically at each station using a Juday net with a mesh size of 180 microns and a mouth opening of 0.1 square meters. One layer was sampled from the bottom to the picnocline, and the second layer was sampled from the picnocline to the surface. If there was strong wind or drift of the vessel, the angle of the wire inclination was taken into consideration. The zooplankton samples were preserved in 4% formalin buffered with borax. The samples were then processed at the Shirshov Institute of Oceanology of the Russian Academy of Sciences (IORAS), by Dr. Ksenia Kosobokova. All zooplankton organisms in a sample were sorted into main taxonomic groups, and for copepods, further to species and stages. Numerous small zooplankton organisms less than 1 mm in size were counted from a sample taken using a stempel pipette, while all larger organisms, especially those that are rare, were counted from the entire sample. The length of copepod prosome was measured from the tip of the cephalosome to the distal end of the last thoracic segment.