Alternative prophylaxis/disinfection in aquaculture - Adaptable stress induced by peracetic acid at low concentration and its application strategy in RAS

Authors: LIU, DIBO - Leibniz Institute Of Freshwater Ecology And Inland Fisheries; PEDERSEN, LARS-FLEMMING - Technical University Of Denmark; Straus, David - Dave; KLOAS, WERNER - Leibniz Institute Of Freshwater Ecology And Inland Fisheries; MEINELT, THOMAS - Leibniz Institute Of Freshwater Ecology And Inland Fisheries

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2017
Publication Date: 5/1/2017
Citation: Liu, D., Pedersen, L., Straus, D.L., Kloas, W., Meinelt, T. 2017. Alternative prophylaxis/disinfection in aquaculture - Adaptable stress induced by peracetic acid at low concentration and its application strategy in RAS. Aquaculture. 474:82-85.

Interpretive Summary: Our labs continue to do research on peracetic acid (PAA) as a relatively new disinfectant/disease-preventative for use in aquaculture. It is a mixture of acetic acid (concentrated vinegar), hydrogen peroxide and water that is considered to be an eco-friendly disease-preventative and disinfectant against fish pathogens. Since PAA degrades to harmless ingredients, it is an extremely useful disinfectant for use in recirculating aquaculture systems. There is a lack of knowledge on how to apply PAA in these systems, and whether using PAA at low concentration can affect fish welfare. Carp in the fish culture tank of one of these systems was exposed to 1 ppm every 3 or 4 days for 5 weeks. We measured the hormone cortisol in the water as it is released by fish as a stress response. We concluded that the concentration we used was an adaptable stressor for carp and regular applications do not cause chronic stress. Regular application has the potential to keep the systems disease-free.

Technical Abstract: The application of peracetic acid (PAA) at low concentrations has been proven to be a broad-functioning and eco-friendly prophylaxis/disinfection method against various fish pathogens. However, there is lack of knowledge on how to apply PAA in a recirculating aquaculture system (RAS), and whether the application of PAA at low concentration can affect fish welfare. In the present study, PAA was applied at 1 mg L-1 in the fish culture tank of a pilot-scale carp (Cyprinus carpio) RAS; the treatments were repeated every 3 or 4 days for 5 weeks. Based on onsite measurement and the developed distribution model, we found that PAA in the fish culture tank was slowly distributed to the reservoir tank and biofilter complex of RAS depending on the tank size and flow rate. As an indication of fish welfare, the stress response was assessed by measuring the cortisol concentration in water released by the PAA exposed carp. The results showed that the increase of cortisol became less pronounced and the decrease of cortisol occurred earlier after repeated applications of PAA, which indicates an adaptation of the stress response to PAA in the carp. We conclude that PAA concentrations less than or equal to 2 mg L-1 is an adaptable stressor for carp and regular applications do not cause chronic stress. Moreover, to avoid potential harm to the biofilter in RAS during PAA application, we suggest that PAA should be applied only to the fish culture tank at a reduced flow rate.