Assessing the Toxicity of Peracetic Acid to Parr, Smolt, and Post-Smolt Atlantic Salmon Salmo salar in RAS Water

The risk associated with the presence of bacterial and fungal pathogens in recirculating aquaculture systems (RASs) has resulted in an industry-wide need for low-cost, safe, and effective disinfectants. The toxicity of peracetic acid (PAA) to Atlantic salmon (Salmo salar) eggs, fry, and fingerlings (~16.3 g) in freshwater RAS water has been previously assessed; however, its toxicity to later juvenile life-stages was yet to be investigated. The 24-h LC50 value of PAA was determined for parr ($$ = 47 g), smolt ($$ = 66.5 g), and post-smolt ($$ = 176.7 g) Atlantic salmon in RAS water static PAA treatments. The 24-h LC50 values were calculated using the trimmed Spearman–Karber (TSK) method and toxicity relationship analysis program (TRAP). TRAP LC50 values for parr, smolt, and post-smolt were 4.26, 4.27, and 4.78 mg/L PAA, respectively, while TSK LC50 values for parr, smolt, and post-smolt were 4.27, 3.94, and 4.65 mg/L PAA, respectively. These 24-h LC50 values provide novel guidance for developing safe PAA treatment protocols for Atlantic salmon parr, smolt, and post-smolt in freshwater RAS, although the influence of varying water quality scenarios needs to be considered.