The continuous application of peracetic acid and UV-C irradiation in rainbow trout aquaculture—a case study under a multifocal pathogen event in a commercial flow-through fish farm

In order to investigate the effects on fish production and health in a commercial aquaculture
facility, rainbow trout (Oncorhynchus mykiss) with an initial average body weight of 41 g
were reared in raceway-channels under a continuous application of either peracetic acid
(0.2 mg PAA L−
1) or ultraviolet C light (UV-C, 316.7–155.8 mWs cm−
2) to the inflowing
water for a total of 183 days. Compared to the control, all performance metrics recorded
in the fish from the PAA and UV-C treatment groups were significantly increased at the
end of the production. To account for the multi-pathogen exposure in the fish farm, regular
fish health examinations were conducted. Pathogens detected were the infectious pancreatic
necrosis virus (IPNV), Flavobacterium psychrophilum, Aeromonas salmonicida, and
Tetracapsuloides bryosalmonae, the causative agent of proliferative kidney disease (PKD).
Furthermore, rainbow trout displayed symptoms of puffy skin disease (PSD). From the
perspective of PSD, the PAA protocol reduced the prevalence and severity of the disease.
At the end of the production cycle, 90% of fish from the PAA treatment remained marketable.
Thus, PAA can be considered a promising tool to protect rainbow trout from PSD in
the future. In contrast, UV-C light did not soothe or prevent PSD outbreaks. However, the
UV-C treatment delayed the development of PKD symptoms in the corresponding group
by around 1 month. The application of the treatment methods investigated resulted in
increased production costs. Overall, the continuous application of the pathogen reduction
methods proved to be positive for fish health and by this for aquaculture.