1. Institute of Biochemistry and Food Science, University of Hamburg, Grindellallee 117, 20146 Hamburg, Germany
2. Institute of Biochemistry and Food Science, University of Hamburg, Grindellallee 117, 20146 Hamburg, Germany and Federal Research Centre for Fisheries, Institute of Fisheries Ecology, Wüstland 2, 22589 Hamburg, Germany
3. Federal Research Centre for Fisheries, Institute of Fisheries Ecology, Wüstland 2, 22589 Hamburg, Germany
4. Institute of Statistics, University of Bremen, Postfach 330440, 28334 Bremen, Germany
5. Institute of Physiological Chemistry, University of Mainz, Duesbergwet 6, 55099 Mainz, Germany