K. Peychev1*, Y. Staykov2, S. Stoyanova2

1Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria 2Department of Biology and Aquaculture, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

Abstract. The interest and the increasing demand for gourmet fish species is a stable tendency in modern aquaculture. This requires the development of intensive production systems with accurately determined and precisely controlled parameters, providing ecological and sustainable farming of a given aquaculture species The aim of the study was modelling and determination of the effect of swimming speed on heat flows within a recirculation system. An additional analysis of the effect of changing average live weight of farmed Russian sturgeon (Acipenser Gueldenstaedtii Brandt.) on converted heat was made. The experimental tank volume was 70 m3, the diameter – 7.5 m and the depth – 1.6 m. It was situated in a closed thermostable premise, part of recirculation system for Russian sturgeon farming. The water in the tank was exchanged 2.3 times per hour under constant temperature of 22°С. In this tank, about 800 Russian sturgeons (Acipenser Gueldenstaedtii Brandt.), with average live weight of 3.5 kg were reared. The effect of fish swimming speed on the resulting thermal power in a recirculation tank followed the same trend irrespective of the live weight of individuals. The swimming speed of fish in recirculation tanks during the summer months should pertain to the technologically allowable minimum, while during the winter months, fish in recirculation systems should be stimulated to swim at a higher speed close to the maximum technologically permissible limit.