Life Cycle and Production of Cyclops vicinus in a Shallow Eutrophic Reservoir

The population dynamics and production of Cyclops vicious (Uljanin) in a shallow eutrophic reservoir were studied over a period of two years. Breeding continued throughout the year, but variations in the rate of egg production gave rise to a succession of generations that could be followed from stage to stage in development. A proportion of stage IV copepodites left the open water in midsummer and remained in diapause until the following spring. Seasonal fluctuations in the finite birth rate were related to changes in the egg stock, mean brood size and the proportion of egg bearing females. Egg development times were determined in culture, and estimates of copepodite instar duration obtained from field data. Production estimates were obtained from the population curves by calculating the number of animals passing through successive stages in each generation. Relationships between population and environmental variables were examined by the method of principal component analysis. There was a marked positive correlation between the C. vicious birth rate and the birth rate of Daphnia hyalina, the only other abundant species in the reservoir.