Stage-specific regression equations between temperature and prosome length of <i>Calanus sinicus</i> copepodids and adults to estimate their seasonal population biomass

The calanoid copepod Calanus sinicus is the biomass-dominant zooplankton in temperate coastal waters of the Northwest Pacific from spring to early summer, and is an important prey for planktivorous fish such as sand lance. To estimate population biomass of postnaupliar C. sinicus, the temperature and body length regression equation was obtained for each instar stage based on prosome lengths of more than 10 individuals in five months at different temperatures (January, March, May, June, and July) between 2018 and 2021. Using the present equations and the known prosome-length and carbon-weight regression equation of C. sinicus, its seasonal population biomass could be estimated from temperature and stage-specific numerical abundance more accurately and easily than before.