Distribution, abundance and production of the copepod <i>Calanus agulhensis</i> on the Agulhas Bank in relation to spatial variations in hydrography and chlorophyll concentration

Abstract

Measurements were made of chlorophyll concentration, abundance and biomass of cope-pods, moulting rates of Calanus agulhensis juveniles and egg production rate of adult females, during two surveys of the Agulhas Bank in spring 1988 and 1989. From these measurements, growth, recruitment and production rates were calculated. Biomass ranged from ∼1 g dry weight m−2 on the western Bank to 5 g dry weight m−2 on the eastern Bank. Calanus agulhensis growth rates were correlated with chlorophyll concentration. Maximum growth rates were observed in 42% of the samples for C1. but in only 10% for C2–C4. Maximum rates were never observed for C5 or adult females. Copepod production increased from 40 mg carbon m−2 daym−1 (western Bank) to 400 mg carbon m−2 daym−1 (eastern Bank); production/biomass ratios ranged from 0 5–0.10 (western) to 0.15 and 0.23 (eastern) Calanus agulhensis accounted for −25 and 60% of the total copepod production on the western and eastern Bank, respectively. Copepod production was at most −20% of the bank-wide averaged primary production rate of 2 g C m−2 day−1.