Copper Sulphate and Rotenone as Fish Poisons

Abstract
A concentration of 3 p.p.m. of copper sulphate was effective in killing fish in the acid waters of four Nova Scotian lakes. The plankton and the bottom fauna were almost entirely destroyed. Rooted aquatic vegetation was largely unaffected. About a year elapsed before plankton and aquatic insects returned in quantity. Mollusks have not repopulated the lakes. Considerable copper remained in the waters for some time, but there was evidence that much was in a combined, non‐toxic form. At 5° and 20°C., concentrations of derris and cubé (5 per cent rotenone) as low as 0.20 p.p.m. killed yearling trout. At 10°C., 0.20 p.p.m. of derris (3 per cent rotenone) was toxic to suckers and lake chubs. In a small lake, 0.25 p.p.m. of derris (5 per cent rotenone) killed eels, lake chubs, sticklebacks, black bass and white perch, but a few eels, lake chubs and sticklebacks survived. Storing derris and cubé powders in a dry condition as long as three years did not affect their toxicity to brook trout. Increased temperature speeded greatly the action of rotenone (derris and cubé powders). Brook trout that had lost their equilibrium in water treated with rotenone revived in untreated water. Planktonic crustaceans were largely destroyed by concentrations of rotenone sufficient to kill fish in natural waters, but aquatic insects, mature and immature, mollusks, Hydracarina, certain rotifers, algae and rooted aquatics were not destroyed. In a small lake in which the original concentration of derris (5 per cent rotenone) was 1.33 p.p.m. the water remained toxic to fish for approximately one month.

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