Biochemical and Biological Characteristics of Tilapia Fingerlings Reared at Different Stock Densities
V. K. ATANASSOV, Y. S. STAYKOV and J. E. MITEV
Thracian University, Agrarian Faculty, BG – 6000 Stara Zagora, Bulgaria
ATANASSOV, V. K., Y. S. STAYKOV and J. E. MITEV, 1999. Biochemical and biological characteristics of tilapia fingerlings reared at different stock densities. Bulg. J. Agric. Sci., 5: 655-658
An experiment was carried out with four progressively increasing stock densities: SD1 – 250 pcs/m3; SD2 – 300 pcs/m3; SD3 – 350 pcs/m3; SD4 – 400 pcs/m3. The results show that increasing stock density up to 400 pcs/m3 causes stress and has a negative effect on the biochemical blood features of Tilapia. The reduced oxygen content in water at the increased stock densities evoked some counterpoise changes in the Tilapia organisms and the reduced partial oxygen tension in blood results in increasing the number of erythrocytes, the hemoglobin, blood sugar and lactate levels. Tilapia fingerlings reared at a stock density of 200 pcs/m3 achieve a standard live weight of 34.9 g. Tilapia reared at a stock density of 300 pcs/m3 have a satisfactory final live weight (26.6 g) and can be used for fattening in the next vegetative period at a smaller stock density. The optimum stock density for rearing Tilapia fingerlings is 250 pcs/m3 and 300 pcs/m3 fish productivity being respectively 8.7 kg/m3 and 8.0 kg/m3.
Key words: Tilapia rearing, partial oxygen tension, hemoglobin, blood lactate levels, fish productivity, stock density
Abbreviations: SD – stock density