Effects of Temperature, Salinity and Fish Number on Oxygen Consumption and Blood Property of Young Rockbream Oplegnathus fasciatus

Abstract

Several factors on oxygen consumption (OC) of rockbream Oplegnathus fasciatus of with a body weight of 74.65±19.61 g and a total length of 14.38±0.99 cm was investigated wherein four studies were designed such as: 1) OC and blood property by water temperature change (20-25-30oC); 2) OC and blood property by salinity change (35-25-15 psu); 3) OC and blood property in different fish number in respiratory chamber (1, 3 and 6 fish); and 4) lethal dissolved oxygen (DO) at different water temperatures (20- 25-30oC). The tendency of OC in temperature experiment increased with temperature, the highest value was found at 30oC. The average of OC during light period was higher than the dark period. Increasing water temperature did not affect the level of hemoglobin (Hb) and hematocrit (Ht). The level of Na+ increased with decreasing water temperature, the highest level was found at 20oC. Level of K+, Cl-, Ca, Mg and osmolality did not affect by increasing water temperature. Changing water temperature had effect on cortisol and glucose level of rockbream, the highest value of cortisol and glucose were at 30oC. The level of total protein did not affect by increasing water temperature. The tendency of OC in salinity experiment increased with salinity. During light period, rockbream consumed oxygen higher than the dark period. The level of Hb and Ht were not affected by changing salinity. The level of Na+ and K+ of rockbream were affected by changing salinity. The highest value of Na+ was found at 30 psu, while K+ was at 25 psu. The level of Cl-, Ca, Mg and osmolality were not affected by changing salinity. The cortisol and glucose level were significantly different by changing salinity. The highest level was found at 15 psu. The level of total protein was not affected by changing salinity. The average of OC of fish number experiment increased with fish number. The average of OC during light period was higher than the dark period. The level of Hb and Ht were not affected by increasing fish number. The level of Na+, K+ and osmolality were not also affected by increasing fish number. Increasing fish number affected on the level of Cl-, Ca and Mg. The highest value was found at 6 fish. Increasing fish number had strong effect on level of cortisol and glucose. The highest level was reported at 6 fish. The level total protein did not affect by changing salinity. The lethal DO level of rockbream increased with the temperature (0.8, 0.9 and 1 mg/L). All blood property components during lethal DO experiment increased with the depletion of DO concentration in every temperature. For recovering experiment, both of fish groups, which was exposed in DO level from 8.6 to 2 mg/L (hypoxia) and 8.6 to 4 mg/L (moderate hypoxia) did not die at the end of experiment. For moderate hypoxia group, it took 24 hours for recovering to normal behavior, while hypoxia group took 1 week to recover. Exposing rockbream in different DO concentration did not effect on the level of Hb and Ht. The plasma of Na+ K+, Ca and osmolality did not effect by exposing in different DO concentration, while the plasma of Cl- and Mg were affected by the depletion of DO concentration. The highest values were in control group. Exposing in low DO concentration had strongly affected on cortisol and glucose. The highest level was observed in hypoxia group. The level total protein was not affected by exposing in low DO concentration. In conclusion, temperature, salinity and fish number, had strong effect on fish activity OC and blood properties of young rockbream. Moreover, temperature had strong effect on lethal DO level and speed of DO decrease. To avoid hypoxia in culture environment and high mortality, aeration should be increased when rockbream is exposed in high temperature, high stocking density in culture farm. Rockbream is not good in osmoregulation. In order to increase aquaculture production, rockbream should not be reared low salinity.