Influence of temperature on the level of aggressiveness of red tilapia (Oreochromis spp [manuscript]
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Date
2017
Authors
Laura Marie C. Benigno
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Abstract
Thirty (30) red tilapia were used to determine level of aggression as affected by different level of temperature. Treatments usedwere 29°C, 31°C, 33°C, 35°C and 37°C and were replicated thrice. During the three-day interaction period, mean ECP of fish at 29°C (2.69±1.67) and 31°C (2.91±1.91) were significantly higher than those at 33°C (1.29±1.91) were significantly higher than those at 33°C (1.29±1.06) and 37°C (1.50±1.04) but comparable to that at 35°C (1.67±1.65). Mean ECP of fish at 35°C was not significantly different from those at 33°C and 37°C. Higher mean ECP was observed at lower temperature, which is in contrast to the results of studies on Nile tilapia where higher ECP was observed during stressful condition i.e. higher temperature. Meanwhile, mean VR of fish was significantly higher at 33°C (2.39±0.39 beats/sec) and 35°C (2.37±0.27 beats/sec) than those at 29°C (1.92±0.39 beats/sec) and 31°C (2.00±0.42 beats/sec) but not significantly different compared to that at 37 °C (2.21±0.65). Mean VR of fish at 29°C was also comparable to that at 31 °C. Mean VR values increased as the temperature increased up to 33°C, then gradually decreased up to 37°C. The decrease in VR was due to increase in the opening of the operculum and mouth during respiration, as the fish were gasping for oxygen that resulted to lesser operculum movements per second. Higher VR was observed at higher temperature, except when the temperature was too high to cause death of the fish; Body color of fish was also observed and skin color of red tilapia exposed in high temperature became more reddish compared to the control or ideal temperature of water. Dominant red tilapia exhibited darker body coloration while the subordinate exhibited paler body coloration. Number of attacks were observed in 10 minutes daily. There is no significant difference on numbers of attacks among the treatments (P=0.153, n=40)., It was also observed that in day 1, Treatment 2 (31°C) had the highest number of attacks (68.33±16.92), while in day 2, Treatment 3 (33°C) showed the highest number of attacks (125.67±69.42), and in day 3, Treatment 1 (29°C) showed the highest number of attacks (88.66±31.78). In Treatments 1, 2, 3 and 4 subordinate fish had died due to wounds caused by the attacks of dominant fish. In Treatment 5, there were mortalities due to the exposure to higher temperature.