Notes on the Use of Derris as a Fish Poison

Abstract

Fisheries workers are finding that powdered derris root is a valuable aid in the elimination of undesirable fish populations. The history of this substance is presented briefly. The early use of derris root as a fish poison and as an ingredient of arrow poisons, and its development as an insecticide are mentioned. Recent papers dealing with its physiological effect on fishes are reviewed. In a series of laboratory experiments it was found that certain species of fresh-water fishes are killed much more readily by derris than are others. The action proved to be somewhat faster in acid than in alkaline waters. Toxicity in an experimental aquarium dropped below the lethal point for fish between twenty and forty-one hours after addition of poison. Toxicity of a stock suspension of 1:100 concentration was reduced by nearly 70 per cent after standing in a darkened closet for thirty-four days. An increase in water temperature from 60° to 74°F. reduced the time of death almost by half. A considerable deterioration was detected in the strength of commercial powdered derris that was exposed to air and subdued light over a period of six months. A concentration of one part powdered derris root (warranted rotenone content 5 per cent) to two million parts of water was found to be sufficient to kill all species of fish tested. Furthermore, no fish was able to survive after the loss of equilibrium, even though transferred to pure, aerated water.