UNIVERSITY OF DEBRECEN CENTRE OF AGRICULTURAL SCIENCES F ACULTY OF AGRICULTURAL SCIENCES DEPARTMENT OF ANIMAL HUSBANDRY DOCTORAL SCHOOL OF ANIMAL HUSBANDRY Leader of Doctoral School: Prof. Dr. Sci. András Kovács Supervisors: Dr. László Pócsi C.Sc. Dr. László Váradi Ph.D. „THESIS OF DOCTORAL (Ph.D.) DISSERTATION” DEVELOPMENT OF ENVIRONMENTAL FRIENDLY COMBINED POND FISH PRODUCTION TECHNOLOGIES by Dénes Gál Debrecen 2006