The effect of water temperature on food transit time and digestive enzymes activity in Caspian kutum (Rutilus kutum) larvae

The present study investigates the effects of water temperature on digestive enzymes activity and food transit time in Caspian kutum (Rutilus kutum) larvae. Caspian kutum larvae (532 ± 0.05 and 543 ± 0.02 mg) were divided into two groups with three replicates and reared at different water temperature i.e. 25.6 ± 0.4°C (T₁) and 18.4 ± 0.1°C (T₂). At the end of the experiment, sampling of intestine was performed at 0, 1, 3, 5, 8, 16, 24 and 30 h after feeding from each treatment. In T₂, food was observed until 24 h after feeding and the intestine was empty 29 h after feeding, while in T₁ 19 h after feeding the intestine was empty. Digestive enzymes activities were higher in T₂ treatment. The peaks of trypsin and alkaline phosphatase enzymes activity were found 8 h after feeding in T₁, while occurred 16 h after feeding in T₂. The highest chymotrypsin and alpha-amylase enzymes activity were observed 5 and 8h after feeding in T₁ and T₂, respectively. These results confirmed remarkable effects of temperature on food transit time and digestive enzymes activity of Caspian kutum.