SEASONAL FLUCTUATIONS IN FECUNDITY AND HATCHING SUCCESS IN THE PLANKTONIC COPEPOD CENTROPAGES-TYPICUS

A mismatch of approximately 2-3 months was observed between reproductive rates and population abundances in the planktonic copepod Centropages typicus, with the highest production at relatively low female abundance and low production at high abundance, during the course of a 2 year study in 1989 and 1990 in neritic waters of the Gulf of Naples. During this period, egg mortality was at times severe, with values as high as 59% in February 1989. The seasonal trend in percentage hatching success did not match seasonal fluctuations in breeding intensity, and was not correlated with variations in environmental variables such as temperature and chlorophyll a. The results of experiments using the fluorescent dye Hoechst 33342 showed that unhatched eggs had been fertilized and that in most cases development had proceeded to an advanced stage before death of the embryo. The causes of high egg mortality are uncertain, but here we give evidence, for the first time, that egg mortality may not only be due to infertility caused by failure to remate.