The Use of Toxaphene as a Fish Poison

Abstract
Standard laboratory bio‐assay tests on the insecticide toxaphene indicated that this chemical is more toxic to fish in hard water than in soft water. Its toxicity to the bluntnose minnow was increased approximately three‐fold by raising the temperature from 50° F. to 75° F. This insecticide was found to be much more toxic to the bluntnose minnow than to any of four aquatic invertebrates tested. The laboratory work supported field observations on two Michigan lakes. Many groups of invertebrates were killed by toxaphene treatment, but they reappeared while the lake water was still toxic to fish. Detoxification of water stored in the laboratory proceeded most rapidly when it was exposed to light, when the oxygen content was high, and when the temperature was high. Hard water (alkalinity, 212 p.p.m.) detoxified more rapidly than soft water (alkalinity, 6 p.p.m.). Detoxification was greatly accelerated by water movements which brought the toxicant in contact with the walls and bottom of the aquarium. The rate of detoxification was increased by the addition of a substrate of glass marbles or gravel. Sand and mud assisted detoxification to a lesser extent. Sterilization of the substrate with dilute formalin and carbolic acid inhibited detoxification; this indicated that microorganisms were responsible for reducing toxicity.

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