Acephate in rainbow trout (Salmo gairdneri): Acute toxicity, uptake, elimination

Abstract The 96‐h LC50of acephate, a water‐soluble organophosphorus insecticide, averaged 2,740 ppm for rainbow trout. Such low acute toxicity is apparently unique among commercial insecticides. Uptake of acephate by trout from water was rapid and reached equilibrium concentrations (4 to 6% of ambient concentrations) in 5 to 8 days. Methamidophos, a metabolite of acephate, formed rapidly, reaching approximately 25% of the acephate concentrations in the fish. Elimination of 50% of acephate and methamidophos from rainbow trout required 1.73 to 2.43 days. Neither acephate nor methamidophos were bioconcentrated in the trout (mean BCF = 0.0533). Predictions of bioconcentration of acephate, based on its water solubility, its octanol/water partition coefficient, or based on relationships developed in other studies, did not, as a rule, agree with our experimental results.