Acute toxicity and histopathology of channel catfish fry exposed to peracetic acid

Peracetic acid (PAA) can potentially be used to treat against freshwater fish pathogens; however, there is a paucity of data about its toxicity to fish. Channel catfish Ictalurus punctatus yolk-sac fry and swim-up fry were exposed to PAA for 48 h in static toxicity bioassays at 23 °C. The test water was 217 and 126 mg/L (as CaCO3) total alkalinity and total hardness, respectively. Probit LC50 values were estimated with the trimmed Spearman–Karber method using nominal PAA concentrations (1.0, 1.3, 1.7, 2.2, 2.8, 3.7, 4.8, 6.3, and 8.2 mg/L PAA). The mean 24- and 48-h LC50 values for yolk-sac fry and swim-up fry was 2.6 mg/L PAA and 1.6 mg/L PAA, respectively; the 24-h no observed effect concentration (NOEC) was 2.2 mg/L PAA for yolk-sac fry and 1.3 mg/L PAA for swim-up fry. Catfish yolk-sac fry were more tolerant of PAA than catfish swim-up fry by about 1.6-fold. Peracetic acid-related histopathology was analyzed in whole-body serial sections of swim-up fry at two selected doses of PAA: 2.2 mg/L (1 h post-treatment) and 1.7 mg/L (48 h post-treatment). Lesions consisted of severe gill damage in fish treated with 2.2 mg/L PAA, and a moderate degeneration of the renal tubule epithelium within the posterior kidney in fish treated with 1.7 mg/L PAA. An advantage to using PAA includes very low environmental impact considerations as it degrades to harmless residues rapidly. Results of the present study are important information needed by the aquaculture industry on a new, potential therapeutant.

► Peracetic acid (PAA) is effective to prevent fungus on catfish eggs; how much PAA is toxic to hatching catfish fry was unknown.
► We found it was more toxic to swim-up fry (~ 7 day old) than to yolk-sac fry (~ 1 day old).
► The safe treatment rate was 1.7 ppm for yolk-sac fry and 1.3 ppm for swim-up fry.