INFLUENCE OF DIFFERENT MEAL SIZES ON GROWTH CHARACTERISTICS OF YOUNG RAINBOW TROUT (ONCORHYNCHUS MYKISS WAL).

This paper presents the results of the effects of different sizes of meals (80%, 90%, 100%, 110% and 120% regarding the amount recommended by the food producer) on the growth characteristics of young rainbow trout (Oncorhynchus mykiss Wal.) aged from 2 to 3.5 months. The experiment was carried out at the Laboratory of Aquaculture, Faculty of Agriculture, University of Banja Luka for a period of 47 days. In the experiment, there were a total of 500 fish, divided into five groups, and placed in the 55-l aquarium with a constant flow of water and the aeration system. The main parameters of water quality were analyzed every day and they included: water temperature 12.64–12.76°C, content of dissolved oxygen 7.83–8.09 mg/l, saturation of water with oxygen 75.47–77.39% and pH value 7.224–7.268. In the end, the average individual weight and body length (±standard deviation) of young rainbow trout, regarding the experimental groups (EG), were reached: EG80 10.53±2.58 g and 9.94±0.76 cm, EG90 12.14±2.97 g and 10.45±0.86 cm, EG100 13.18±2.91 g and 10.67±0.82 cm, EG110 13.80±3.14 g and 10.82±0.78 cm, EG120 14.58±3.63 g and 10.81±1.11 cm. Statistically highly significant differences were found between the means of experimental groups (p < 0,01). The coefficient of condition of young rainbow trout at the end of the experiment was similar in the treatments EG80, EG90, EG100 and EG110 (1.06 to 1.09), and it was the highest in the treatment EG120 (1,15±0,17). Generally, it can be said that increasing of the size of meals up to 10% above the recommended value does not cause significant differences, and if the increase is greater than 10%, statistically significant difference in body weight occurs.