Einfluss von Temperatur auf die Energie-Budgetierung bei antarktischen und borealen Fischen

Abstract

This thesis investigates how temperature and energy allocation affect the growth of fish species. In a comparative approach two eelpout species, one temperate, Zoarces viviparus, and one Antarctic eelpout, Pachycara brachycephalum, were studied. Age, growth and fecundity in the field were investigated. The energy demands of metabolism, growth and excretion as well as body composition and lipids were measured and analysed at different temperatures in long-term acclimation experiments. In Pachycara brachycephalum the predominant lipid class in muscle and liver tissue over the whole temperature range are storage lipids. Zoarces viviparus changes the lipid composition to these storage lipids in the cold. The pronounced lipid metabolism in the Antarctic eelpout may be the result of evolutionary processes of high mitochondrial densities and low metabolic rates and the high availability of a lipid enriched diet indicated by the stable isotope analyses. The field growth patterns of Pachycara brachycephalum show in its natural habitat a lower growth rate than that of the temperate eelpout population in the Wadden Sea, whereas the experimental growth rate of the Antarctic eelpout was higher. Both the Antarctic and the temperate eelpout display optimum growth temperature close to their habitat temperature (12 degrees C for the temperate eelpout) or their evolutionary approach to the habitat (4 degrees C for the Antarctic eelpout, who most like entered Antarctic waters via Deep Sea). The food conversion efficiency of the Antarctic eelpout is high. This ability to ingest and absorb energy in short periods of local appearance and to store this energy for starving periods is crucial in an environment where food supply is unstable and pulsed. The slow field growth rates of the Antarctic eelpout are due to habitat temperatures below the thermal growth optimum and to food limitation.