Feeding selectivity and egg production of Calanus helgolandicus in the English Channel. Limnology and Oceanography 45: 44–54

Copepods are able to discriminate between different foods on the basis of particle size and nutritional quality. However, the extent of selective feeding behavior and the mechanisms controlling it in the field are still poorly understood. In this study, we investigated selective feeding behavior and egg production for Calanus helgolandicus feeding on natural phytoplankton (using high-performance liquid chromatography techniques), and egg production, at a coastal station off Plymouth with the annual phytoplankton cycle from July 1996 to June 1997. The phyto-plankton succession included biomass peaks of dinoflagellates, prymnesiophytes, and diatoms. C. helgolandicus showed little selective feeding behavior throughout the study with a slight preference for diatoms. The influence of the diet composition on egg production was analyzed using forward stepwise regression methods. Prymnesiophytes and diatoms were shown to have positive effects whereas the effect of dinoflagellates was negative. The effect of the different phytoplankton peaks is analyzed and discussed in relation to the phytoplankton taxonomic composition and dietary diversity. Since the initial controversies (see Harvey 1937) the abil-ity of calanoid copepods to discriminate between different particles, either as a function of size (Frost 1972) or of food quality (Huntley et al. 1983; Cowles et al. 1988) has been clearly demonstrated in laboratory experiments using phy-toplankton cultures. Video techniques have also helped us to understand the mechanisms used by copepods to detect, cap-ture, and manipulate different particles as a function of their characteristics, their concentration, or the physical environ-ment (Paffenhöfer 1988; Price 1988; Kiørboe and Sai