| With the rapid development of marine fish culture in China,the scale of aquaculture is expanding and the degree of intensive high-density aquaculture is increasing.The large-scale outbreak of marine fish diseases has shown a rising trend,causing huge losses to the fishery economy.Vibrio parahaemolyticus and Crytocaryon irritans are common diseases in marine fish culture,which easily cause fish death and seriously endanger the healthy development of fish culture due to their high speed of transmission and strong tolerance.Conventional control methods have some problems,such as poor effect,high cost,low safety,drug residue and pollution problems,etc.Therefore,it is of great significance to use a new environmentally friendly method to control the two kinds of disease.In this paper,the technique of highly efficient generation of hydroxyl radical(·OH)by atmospheric pressure ionization discharge and the industrial culture of grouper were combined.The Epinephelus coioides was used as the culturing object.The system and method of ·OH control of grouper disease under the condition of factory culture were established,and the inactivation of V.parahaemolyticus and theront were studied.The control effect of ·OH on V.parahaemolyticus and C.irritans were investigated.The main results are as follows:(1)A system of ·OH prevention and control of grouper diseases under the condition of factory culture was established in the Xiaodeng Island Epinephelus sp breeding base,Xiamen.The parameters of the equipment for ·OH treatment were adjusted and the change curve of TRO concentration with time in pure sea water and fish culture were determined,which provided the experimental parameters for the next practical disease-control experiment.(2)The rapid and efficient lethal effect of V.parahaemolyticus was achieved using·OH treatment equipment.The ·OH lethal threshold of V.parahaemolyticus with concentration of 2.1×105?107 CFU/mL was 0.40?0.70 mg/L,and the lethal time was only 1 s.The morphological change of V.parahaemolyticus before and after ·OH treatment was observed by scanning electron microscope,suggesting that the treated bacteria were ruptured.(3)The control experiment of V.parahaemolyticus disease was carried out by using the system-OH.The results showed that ·OH had a remarkable effect on the control of V.parahaemolyticus disease.After immersing V.parahaemolyticus disease Epinephelus coioides in ·OH solution of 1.0 mg/L for 1 h,the inactivation rate of Vibrio on the surface of infected fish reached 100%.The inactivation rates of total number of colonies,colonies of Vibrio,total coliform group and heat-resistant coliform group were all 100%.The survival rate of diseased fish increased obviously,and the dissolved oxygen increased 57.9%afte ·OH treatment.The removal rates of ammonia nitrogen,nonionic ammonia and nitrite were 88.8%,90.7%and 88.7%,respectively.Besides,the water quality reached the standard of "Fishery Water quality Standard"(GB11607-1989)and "Mariculture Water discharge requirement"(SCT 9103-2007).(4)·OH also had a significant killing effect on the isolated larvae of C.irritans,and the lethal threshold for theront of 800 per milliliter was 0.52 mg/L and the lethal time was 30 s.By using the system of ·OH to control the diseases of Epinephelussp,the results showed that ·OH had a remarkable therapeutic effect on Crytocaryon irritans.After immersion with ·OH solution of 1.0 mg/L for 1 hour,the trophont on the surface of the infected fish fell off.The inactivation rates of total number of colonies,colonies of Vibrio,total coliform group and heat-resistant coliform group were all 100%,which reduced the risk of secondary outbreak of bacterial disease.After ·OH treatment,the water quality of cultured seawater reached the standard of "Fishery Water quality Standard"(GB11607-1989)and "Mariculture Water discharge requirement"(SCT 9103-2007). |
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