1. United States Department of Agriculture, Agricultural Research Service; Harry K. Dupree - Stuttgart National Aquaculture Research Center; PO Box 1050, Stuttgart Arkansas 72160 USA
2. Department of Ecophysiology and Aquaculture; Leibniz-Institute of Freshwater Ecology and Inland Fisheries; Müggelseedamm 301, 12587 Berlin Germany
3. Section for Aquaculture; North Sea Research Centre, Technical University of Denmark; PO Box 101, DK-9850 Hirtshals Denmark