Estimation of production of the copepod Calanus sinicus during spring in the northern East China Sea

Abstract

We estimated the production of the copepod Calanus sinicus, including somatic production of copepodite stage 1 (CI) to copepodite stage 5 (CV) and egg production of adult females, to elucidate the role of C. sinicus during spring in the northern East China Sea, including the southern waters of Korea. To estimate the somatic production of the copepodites, an empirical equation for broadcasters (Hirst & Bunker 2003) was used. The total biomass of the C. sinicus population, including CI to adult males and females, ranged from 0.11 to 30.23 mg C m⁻³, with a mean of 8.69 mg C m⁻³. The egg production rate (EPR) of adult females of C. sinicus, measured over 24 h of shipboard incubation, ranged from 0 to 14.9 eggs female⁻¹ day⁻¹ (mean 5.8 eggs female⁻¹ day⁻¹), equivalent to mean 33.6 µg C m⁻³ day⁻¹. The weight-specific EPR (WSEPR) of adult females averaged 0.023 day⁻¹, and significantly increased with increasing water temperature at 5 m depth and surface chlorophyll a concentration, respectively. WSEPR decreased with increasing body mass of individual adult females. The total production of the C. sinicus population ranged from 0.02 to 3.67 mg C m⁻³ day⁻¹ (mean 0.91 mg C m⁻³ day⁻¹) and the depth-integrated mean total production was estimated to be 52.72 mg C m⁻² day⁻¹. CV production accounted for 54% of the total production. By contrast, EPR contributed on average only 3.7% of the total production rate. Our estimate of the production of C. sinicus can be applied for potential comparisons of region-specific copepod production.