Effects of Different Temperatures on the Antibacterial, Immune and Growth Performance of Crucian Carp Epidermal Mucus

Fish is one of the important sources of energy and protein, and proper water temperature is key to successful fish breeding. The authors of this study evaluated crucian carp growth, mucus antibacterial properties, and immune indicators at 17, 21, 24, 27, and 31 degrees C. The results indicated that in the range of 17-31 degrees C, the resistance of epidermal mucus to Vibrio harveyi decreased with temperature rising. At 24 and 27 degrees C, the activities of lysozyme and catalase significantly increased; alkaline phosphatase activity, superoxide dismutase activity, and total protein concentration first increased and then decreased with rising temperature; the highest values were observed at 24 degrees C, with increases of 56.55%, 26.64%, and 44.52%, respectively, compared to those under the 17 degrees C treatment. When the treatment reached 27 degrees C, the temperature had an effect on the growth and antibacterial properties of crucian carp, and the activities of alkaline phosphatase and superoxide dismutase were significantly reduced. At temperatures of 17-24 degrees C, the survival rate of crucian carp could reach more than 93%, and at the temperature of 24 degrees C, the specific growth rate reached the highest value of 43.29%. Therefore, the most favorable temperature for the long-term breeding of crucian carp was found to be 24 degrees C. This study provides a favorable experimental basis for the establishment of intelligent aquaculture systems and the setting of water environment parameters.