Preliminary investigations on the comparative chronic toxicity of four dietary arsenicals to juvenile rainbow trout ( Salmo gairdneri R.)

Abstract

Juvenile rainbow trout were fed semi-purified diets in eight-week growth trials to compare the toxicity of four dietary arsenicals: arsenic trioxide (AT); disodium arsenate heptahydrate (DSA); dimethylarsinic acid (DMA); and arsanilic acid (AA). Toxicity responses of reduced growth and feed consumption, and altered feeding behaviour, were noted at all levels of supplementation of AT and DSA (137–1477 μg As/g diet). In contrast, even at the highest levels of supplementation (1497 μg As/g diet as DMA, and 1503 μg As/g diet as AA) the organic arsenicals did not result in these toxicity signs. Carcass arsenic concentration showed a dose-response relationship to dietary arsenic concentration and exposure rate, for each of the arsenicals investigated. At lower levels of exposure, dietary DSA yielded the highest carcass arsenic concentrations, while at higher levels, dietary AT yielded the highest residues. The ‘no observed effect concentration’ (NOEC) for dietary arsenic lies between 1 and 137 μg As/g diet for DSA, between 1 and 180 μg As/g diet for AT, and is at least 1497 μg As/g diet for DMA and AA. It was concluded that disodium arsenate was the most toxic to juvenile rainbow trout of the four dietary arsenicals studied.