The population dynamics of Pseudocalanus acuspes in the Central Baltic Sea were studied from March 2002 to May 2003 on a monthly basis. All stages were present year round with a stage shift from nauplii to older copepodite stages over the course of the year. Biomass, estimated from prosome length, peaked between May and September with maximum recorded values of 594 and 855 mg C m-2 in May 2002 and 2003, respectively. Differences in biomass between stations up to a factor of 20 were observed especially in April/May and October. Mean egg production rate (EPR) showed a seasonal course and was highest in April 2002 and 2003 with 3.6 and 2.1 eggs f-1 day-1, respectively, corresponding to a mean weight-specific egg production rate (SEPR) of 0.13 and 0.04. Egg production seems to be limited by food from May on. Stage durations determined from moulting experiments turned out to be extremely long. Maximum growth rates based on stage durations of 15-25 days at 4°C in May and July 2003 amounted for 0.03-0.05 day-1 in CI-CIV. Comparing these rates with rates derived from temperature-development relationships for P. acuspes from the literature resulted in five times higher growth rates for the latter case. Secondary production reached values up to 9.1 mg C m-2 day-1 (method for continuously reproducing populations) and 10.5 mg C m-2 day-1 (increment summation). © 2006 Springer-Verlag.