Abstract
We investigated seasonal variations of population structure and depth distribution of
Calanus sinicus in northern Kagoshima Bay. Animals were abundant during April to June when
chlorophyll a concentrations were high. Young copepodites or adults appeared over the seasons,
however, copepodite stage 5 dominated when the population abundance was the lowest during
August 2009 and July 2010. We found little indication of seasonal vertical migration since all
developmental stages occurred above 50 m and below 100 m throughout the year. RNA:DNA
ratios revealed no significant decline throughout the year. These results suggest that Calanus
sinicus reproduces throughout the year and does not experience a deep-water dormancy period in
northern Kagoshima Bay.
