Individual-based model for population dynamics of vendace (Coregonus albula) in Lake Pyhajarvi, southwest Finland

The population dynamics of vendace have been analysed from data collected from Lake Pyhajarvi (SW Finland) during 1971-1992. We built an individual-based population model to determine the essential causes for the observed fluctuations. The basic unit of the model is a single individual with vital parameters derived from our previous empirical findings. The equations deal with probabilities of death and they produce the expected number of vendace in different stages of life-residuals of every equation are included as random factors. Investigations with an invidual-based model revealed that causes for the observed fluctuations of vendace in Lake Pyhajarvi were intraspecific competition, stock-recruitment relationship, mortality in larval phase and abiotic environmental variation. Fishing patterns were also an important regulatory factor in the population dynamics of vendace.