The rates of daily egg production were estimated for the egg sac-carrying calanoid copepod Pseudodiaptomus marinus SATO by an integration of data from field and laboratory investigations. The brood size was positively related to the body size of adult females which was in turn negatively related to the environmental temperature. The development time of embryos (D in days) was a function of temperature (T in °C) as expressed by the equation: D=448 (T - 1.0)^. Under excess food conditions, the duration from the hatching of brood to the production of the successive one was generally short and constant (0.14 d) at different temperatures. Assuming sufficient food supply and continuous breeding, the daily reproductive rates of the natural population of P. marinus were high from May to October but much lower from January to March. The ratios of daily egg production: female body weight increased linearly with temperature
