Reproductive success in Calanus helgolandicus as a function of diet and egg cannibalism

Calanus helgolandicus females were incubated for 6 to 25 d in single and mi xed diets of the diatom Coscinodiscus curvatulus and the dinoflagellate Gym nodinium sanguineum using 2 incubation protocols, and fecundity, hatching s uccess, egg cannibalism and faecal pellet production were measured. Both fe cundity and hatching success were significantly reduced by single or mixed diets containing high concentrations of diatoms. The deleterious effect of the diatom was diminished when females were fed diets containing low diatom concentration and also when egg cannibalism represented ca >20% of the tot al daily egg production. Egg cannibalism was higher with the wheel-incubati on method than with the vial-incubation method. The results suggest that di atom inhibition of copepod reproduction can be reduced in various ways, inc luding decreasing the diatom concentration, switching from diatom to dinofl agellate diets, increasing the diversity of food items and also by egg cann ibalism (eggs are of high nutrient value).