Zooplankton abundance, biovolume and size spectra at western boundary currents in the subtropical North Pacific during winter 2012

• Zooplankton community was studied at western boundary currents in North Pacific.
• ZooScan system combined normalized biovolume size spectra and taxonomic composition.
• Zooplankton community was directly/indirectly regulated by the physical processes.
• Zooplankton community was coupled with geographical patterns of different currents.

Horizontal changes in mesozooplankton abundance, biovolume and size spectra at western boundary currents in the subtropical North Pacific during winter 2012 were evaluated by ZooScan measurement on samples collected by net towing from 23 stations. Zooplankton abundance and biovolume ranged from 35.1 to 456.8 ind. m− 3 and 4.3 to 231.7 mm3 m− 3, respectively. Copepoda were the most dominant species, followed by Chaetognatha and Tunicata. According to the Bray–Curtis cluster analysis based on biovolume of zooplankton size classes of each taxonomic group at intervals of 1 (log2 mm3 ind.− 1) between − 6 and 12 and considering the effect of regional factors, zooplankton communities were classified into four groups, which basically coincided with the geographical patterns of different currents: the North Equatorial Current (NEC), the North Equatorial Counter Current (NECC), the Kuroshio Current (KC), and the Mindanao Eddy (ME), respectively. The largest and lowest biovolumes were observed in the NECC region and the NEC region, respectively, and both were dominated by the 0.3 to 1 mm equivalent spherical diameter (ESD) size class, while the ME region was dominant by the 1 to 2 mm ESD size class. The slopes of the normalized biovolume size spectra for each group were slightly lower than − 1 (range from − 0.85 to − 0.92), which indicates that zooplankton communities in the study area were characterized by low productivity and high energy transfer efficiency.