Effect of Exposure to Potassium Permanganate on Stress Indicators in Channel Catfish Ictalurus punctatus

Juvenile channel catfish Ictulurus punctatus were exposed to 1× (0.44 mg/L), 3× (1.32 mg/L), or 5× (2.19 mg/L) the recommended therapeutic concentrations of waterborne potassium permanganate (KMnO4) for 36 h to determine the toxicity of the chemical. The fish were observed for 14 d after exposure. Gill, liver, and blood samples were collected before exposure, at 12, 24, and 36 h of exposure, and at 48‐h intervals for 14 d thereafter. Analysis of homogenized gill tissue showed a transient increase in manganese content that quickly disappeared once exposure was discontinued. Fish exposed to the 3× and 5× concentrations of KMnO4 experienced 9 and 50.6% mortality, respectively. Plasma cortisol was elevated more than ten‐fold at the 5× concentration. Both plasma chloride and osmolality were significantly reduced at the 3× and 5× concentrations but were unchanged at the 1×. Packed cell volumes (PCV) of whole blood rose significantly in response to 3× and 5× concentrations of KMnO4 Mortality may have been the result of blood electrolyte depletion as indicated by increased PCVs, loss of chloride, and reduced osmolality. All stress indicators measured, except PCV at the 5× concentration, were indistinguishable from unexposed controls within 48 h after exposure was discontinued. At the l× concentration (the concentration most like that employed in a disease treatment) no changes were observed in any stress indicators measured suggesting that KMnO4 may be safely used as a disease therapeutant for channel catfish.