Flat trays, 40 X 60 cm, were filled with about 3 1 of filtered (0.22 pm> seawater and 40,000 adult Tisbe copepods consisting predominantly of oviger females. Each tray was filtered daily through two filters, one of mesh size of 220 pm retaining almost only oviger females and one of 40 pm to maintain nauplii hatched in the interim period. The adults collected on the filter were replaced in the rearing trays with fresh seawater and fresh algae were added. To each tray about 400 ml Rhodomonas was added at concentrations of around one million cells ml-‘. The nauplii harvested were counted daily. Temperature was around 18°C.