Ph.D. project by Fredrik Nilsson (Informatics and Mathematical Modelling, DTU)
Supervisors: Bo Friis Nielsen(Informatics and Mathematical Modelling, DTU), Jan E. Bayer (Danish Institute for Fisheries Research) and Henrik Mosegaard(Danish Institute for Fisheries Research)
Herring and sprat form schools in the morning, these dissolve at night. This study will try to describe the pattern of formation and dissolution of schools, develop a model for the process and finally, evaluate the consequences on the population dynamics in the Baltic Sea. Optimality concepts have been used with great success in evolutionary biology, their impact on ecology has been smaller. However, since individuals and their behaviour are products of evolution, there is good reason to assume that the behaviours that are critical to survival are in some sense optimal. Optimal theory will be used to see if we have understood the important variables and constraints that underlie the behaviour observed. There are several reasons to form a school, which naturally depends on who you are - wolves form packs and sheep form herds. This study will try to understand why sprat form schools, and why the schools dissolve. The primary suspect as a formatting factor is predation. The schooling process will be studied using echo-sounder data, the impact of predation can be evaluated from stomach data from cod. Stomach data from sprat could be used to see if they are wolves or sheep. The usual population models assume that the populations are a well-mixed soup of predators and prey. Schools and rather intelligent predators might have a huge impact on the population dynamics, the models of the variation in schooling during the day could be useful in developing alternative models.
Figure. Left side - echogram shows herring and sprat during the night — each “worm” is probably a fish, the brown wavy line is the bottom, right side shows schools, it is registered 2 hours after the recording on the left side.