Eucalanus bungii, that reaches about 7 mm in body length, is a large copepod distributed in the subarctic North Pacific Ocean. This species occupy approximately 16% on the zooplankton biomass in the Oyashio region. After hatching from eggs, copepods have six nauplius stages and six copepodite stages with molting occurring between each developmental stage. This species dives into the deep sea (between 500 and 1,000 m) for diapause between fall and winter when phytoplankton is scarce. The developmental stage at which this species enters diapause ranges from copepodite stage 3 to 5, and depending on the area of ocean, Eucalanus bungii is considered to have a two-year generation time.