Feeding selectivity and egg production of Calanus helgolandicus in the English Channel

Copepods are able to discriminate between different foods on the basis of p article size and nutritional quality. However. the extent of selective feed ing behavior and the mechanisms controlling it in the field are stili poorl y 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 producti on, at a coastal station off Plymouth with the annual phytoplankton cycle f rom July 1996 to June 1997. The phytoplankton succession included biomass p eaks of dinoflagellates, prymnesiophytes, and diatoms. C. helgolandicus sho wed little selective feeding behavior throughout the study with a slight pr eference for diatoms. The influence of the diet composition on egg producti on was analyzed using forward stepwise regression methods. Prymnesiophytes and diatoms were shown to have positive effects whereas the effect of dinof lagellates was negative. The effect of the different phytoplankton peaks is analyzed and discussed in relation to the phytoplankton taxonomic composit ion and dietary diversity.