TOXICITY OF FORMALIN, MALACHITE GREEN, AND POTASSIUM PERMANGANATE TO THE GLASS EEL STAGE OF AMERICAN EEL1

Abstract

ABSTRACTThe toxicity of formalin, malachite green, and potassium permanganate to the glass eel stage of American eel, Anguilla rostrata, was determined in glass jars containing three liters of aerated well water at 21 C for a period of 96 hours. Exposure to concentrations of formalin up to 50 ppm for 96 hours and up to 500 ppm for 1 hour produced less than 50% mortality in 96 hours, and 96‐hour LC50 could not be determined. The 96‐hour LC50 for malachite green was 0.25 ppm with a 95% confidence interval of 0.20‐0.29 ppm. The 24‐hour LC50 for potassium permanganate was 3.29 ppm with a 95% confidence interval of 2.11‐3.62 ppm. After 24 hours, mortality in potassium permanganate increased so greatly from 30% in 3 ppm to 100% in 4 and 5 ppm that the LC50 could not be determined. All chemicals tested appeared to be safe to apply to glass eels at concentrations commonly used to control parasites on cultured fishes.