Optimal stocking density and daily feeding rate of rainbow trout (oncorhynchuc mykiss) in sea cages

SUMMARY Optimal Stocking Density and Daily Feeding Rat® of Rainbow Trout (Oncorhynchus mykiss) In Sea Cages, The main aim of this study was to investigate the optimal stocking density and daily feeding rates depending on water temperature and live weight of rainbow trout cultured in sea cages in the South eastern Black Sea region. During the study two experiments, each lasting 180 days, were carried out. At monthly intervals about 10 % of the fish in each cage was taken as sample and weighed for determining growth, food conversion, feeding rates and condition factor. Fish in cages were fed ad libitum by hand and mortality was also recorded daily. Means of growth, food conversion and feeding rates were compared using analysis of variance and the differences between groups were further evaluated using the Duncan test. In the first experiment fish with initial mean weight of 30 g were stocked at three densities and reached to 16.0, 11.3, 7.4 kg/m3 final density and 633.9±10.4, 593.5±9.8, 589.4±15.2 g body weight at the harvest. Spesific growth, food conversion and feeding rates varied between 0.786-3.264 %, 1.54-2.04 and 1.49-4.89 %, respectively. In the second experiment fish with initial mean weight of 200 g were stocked at four densities and reached to 40.2, 31.8. 22.4, 18.9 kg/m3 final density, 1038.3±22.5, 1099.8±13.7, 1167.2±20.0, 1227.5±28.1 g body weight at the harvest. Spesi fic growth, food conversion and feeding rates varied between 0.461-1.892 %, 1.71-2.13, and 0.97-3.15 %, respectively. Mor tality rate was quite low and varied from 3.63 to 4.57 % in both experiment. At the end of the study, a negative correlation between stocking density and growth has been found, but stocking density did not appear to affect growth for the populations held at density around 20-25 kg/m. However in order to increase biomass per unit volume stocking density should be around 40 kg/m. The results indicated that feeding rate of 0.97-4.89 % of live weight per day was sufficient. Key words: Rainbow trout (Oncorhynchus mykiss), cage culture, stocking density, growth, feeding rate, food conversion ratio. VI