Toxicity of the organophosphorus defoliant def to rainbow trout (Salmo gairdneri) and channel catfish (Ictalurus punctatus)

Abstract

Ninety-day partial life cycle toxicity tests were conducted to determine the effects of the organophosphorus defoliant S, S, S-tributyl phosphorotrithioate (DEF), on rainbow trout (Salmo gairdneri) and channel catfish (Ictalurus punctatus). Exposure concentrations were 0, 0.76, 1.2, 1.7, 2.7, 3.6, 6.5, and 9.5 μg/l for rainbow trout and 0, 0.77, 2.0, 4.8, 10.0, and 19.6 μg/l for channel catfish. In rainbow trout growth was reduced by DEF concentrations ≥ 1.2 and survival by concentrations ≥ 3.6 μg/l; growth and survival of channel catfish were reduced by DEF concentrations ≥ 4.8 and 19.6 μg/l, respectively. DEF adversely affected vertebral biochemical composition and mechanical properties of both species. DEF was not highly accumulative in the tissues of either species and was eliminated rapidly when the fish were transferred to contaminant-free water. The determination of safe environmental concentrations of DEF depends partly on the species tested and the biological response measured. Application factors classically used to estimate safe environmental concentrations of contaminants may not be applicable to some of the new-generation organophosphate compounds in relation to cold-water species such as rainbow trout.