Abstract
The size distribution of a cohort at the end of the growing season will affect the survival through the winter season because of size-dependent capacity to withstand starvation. An understanding of the development of size variation is therefore fundamental to be able to predict recruitment variation in exploited populations like fish populations. Present knowledge has advanced positive size-dependent performance and positive growth autocorrelation as factors that may generate increased size variation within cohorts. The suggested mechanisms underlying size-dependent performance and growth autocorrelation are, however, quite diverse and generally only partly supported by empirical data. We aim to investigate possible mechanisms giving rise to size variation within cohorts during the first year from eggs through early ontogenetic niche shifts using a combination of field studies, experiments and modeling. The experiments include studies of the origin of initial size variation and the effects of ontogenetic niche shifts and predation on size variation. Modeling studies using a modeling approach specifically designed to handle size-based dynamics will theoretically investigate the effects of the mechanisms studied in the experiments separately and in combination. Field studies will be carried out to yield data on individual growth and cohort size formation in relation to hatching date, resource use, habitat use and resource levels.
Sweden