Study on effect of music on behavioral changes, mortality percentage and some of the physiological indices of rainbow trout (Oncorhynchus mykiss) in laboratory condition and in recirculating aquaculture system(RAS)

The effect of music on behavioral changes، mortality percentage and some of physiological indices of Rainbow Trout (Oncorhynchus mykiss) in weight group of 50 ± 2 g، in three stages with the duration of 120 h was studied. At the first stage، in order to chose the type of music، fishes were exposed to three types of classical، traditional Iranian music and sound of water flow in nature everyday. At the second stage in order to determine the time of exposure، the selected music was played for duration of 1، 3 and 6 hours per day. Based on behavioral parameters، including slow swimming near and under speaker with significant reduction in blood cortisol during the first 24 hours (22. 41 ± 1. 7 to 12. 48 ± 0. 6 ng/ml) (P<0. 05) and no mortality during the test، classical music was selected at the first stage. At second stage، according to the same changes in behavioral parameters and significant decrease in blood cortisol (30. 23 ± 2. 1 to 16. 65 ± 1. 2 ng/ml) (P<0. 05) and no mortality، the period of 1 hour for classical music was selected. In the third stage of the test، based on the results of the first two stages، to evaluate the quality of the results in a recirculating system the classical music with duration of one hour per day was played for rainbow trout. Behavior changes، including slow swimming near and under the speaker with no mortality and significant reduction in blood cortisol in hours of 0، 12، 24، 72 and 120 (37. 80 ± 2. 1، 32. 69 ± 2. 8، 20. 93 ± 1. 3،20. 13 ± 1. 5 and 11. 62 ± 0. 8 ng/ml respectively)، glucose، (67. 00 ± 4. 1، 60. 66 ± 2. 2، 57. 11± 4. 9، 53. 33 ± 3. 6 and 31. 94 ±1. 3 mg/dl respectively) (P<0. 05) and a significant increase in Hepatosomatic index (HSI) (0. 96 ± 0. 07، 1. 21 ± 0. 06، 1. 26 ± 0. 06، 1. 27 ± 0. 07 and 1. 28 ± 0. 06 % respectively) (P<0. 05)، is positive effect of classical music on improvement of physiological mechanism and calm increase in the fishes that we can attribute.