Mikael van Deurs:
The Life-cycle of Sandeel - Adaptations to a seasonal environment, from the perspective of a forage fish

The aim of the Ph.D. study was to identify and describe critical ecological and physiological links between climatic variability and the life-cycle of a highly abundant and commercially targeted prey fish (sandeel, Ammodytes ssp.). The obtained results are suggestive of several pathways through which variation in the seasonal cycle of prey availability, prey species composition and sea temperature potentially could influence at the population level. Those pathways involve: i) temporal mismatches between peaks in food availability and the feeding periods, ii) intra-specific competition among juveniles exposed to time-constraints on growth and reserve accumulation prior to winter, and iii) life-history adaptations in relation to size at maturation and the overwintering. A single main message of this work is that neglecting the importance of the overwintering phenomenon and seasonality in the environment may lead to failure in understanding population fluctuations of not only sandeel but possibly forage fish populations in seasonal environments in general.