Abstract.The occurrence of pianktonic stages of the scyphomedusaAurelia auritaLAM. in monthly samples, from May 1983 to July 1985, was studied in Elefsis Bay (Saronikos Gulf, Greece). Results showed that the medusae biomass had its maximum value during summer, followed by a sharp drop during fall and winter. The major peak for the ephyrae liberation was during January‐February, when zooplankton biomass reached its maximum. The vertical distribution ofA. auritain relation to light intensity is discusse