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Periodic bacterial control with peracetic acid in a recirculating aquaculture system and its long-term beneficial effect on fish health

Dibo Liu, David L. Straus, Lars-Flemming Pedersen, Thomas Meinelt
Aquaculture 2018 v.485 pp. 154-159
Cyprinus carpio, antibacterial properties, bacteria, cortisol, disinfection, fish, fish culture, fish health, kidneys, leukocytes, microbial colonization, peracetic acid, recirculating aquaculture systems, respiratory burst, risk reduction, stress response, tanks, water flow
Fish in a recirculating aquaculture system (RAS) live with abundant microorganisms. These can become a health threat when the fish immune system cannot counterbalance the pathogenic microbial colonization. Therefore, microbial control in a RAS can potentially reduce the risk of infections and hence improve fish health. In the present study, a periodic microbial control was performed in a RAS with 16 tanks stocked with mirror carp (Cyprinus carpio) for 3months. Half of the fish culture tanks were treated with 1mgL−1 peracetic acid (PAA) twice per week, while the other half remained untreated. The water circulation was interrupted immediately before each PAA-treatment, and resumed after 3h. The total aerobic bacterial density was similar in all culture tanks, except during the PAA-treatments and the concurrent circulation interruptions. During these periods, the bacterial density decreased up to 90% in PAA-treated water, while a 6-fold bacterial increase was observed in untreated water. In the first 2months of treatment, PAA-exposed fish showed lower plasma cortisol concentration than the unexposed fish. Subsequently, the trunk kidney leukocytes of PAA-exposed fish showed stronger respiratory burst than the unexposed fish. By the end of the experiment, the PAA-exposed fish had better gill morphology, compared to the unexposed fish. The present study indicates that periodic disinfection of culture water in a RAS with PAA could transiently reduce the suspended bacteria density, modulate the fish stress response, and have an overall beneficial effect on fish health in the long term.