Use of Rotenone as Piscicide: Toxicity Levels in a Few Common Freshwater Predatory and Weed Fishes

Toxicity of rotenone was studied in a few common freshwater predatory and weed fishes through wet laboratory experiments for its use as a piscicide during pond preparation. Cube root powder (CRP) (ENT-133 Rotenone) containing 9% rotenone was used as the toxicant source. Lethal concentration of CRP for these common predatory and weed fishes varied between 0.75–2.70 mg L^?1 (0.068–0.243 mg L^?1 of rotenone). Acute toxicity study revealed Puntius sophore to have more susceptibility to rotenone toxicity with 24 h LC₅₀ value of CRP at 0.50 mg L^?1 (0.045 mg L^?1 rotenone) compared to 1.17 mg L^?1 (0.105 mg L^?1 rotenone) in Anabas testudineus and 1.90 mg L^?1 in Channa punctatus (0.171 mg L^?1 rotenone); while Heteropneustes fossilis showed higher tolerance with 24 h LC₅₀ value at 2.42 mg L^?1 (0.218 mg L^?1 rotenone). Such result suggested rotenone toxicity to depend on the respiratory behavior of fish. The marginal reduction in 48 h LC₅₀ of CRP compared to its 24 h value and no fish mortality beyond 48-h in all tested species suggested faster degradation of the toxicant in water. Since application of the piscicide aims at eradication of all commonly available species of predatory and weed fishes in the culture pond, the study suggested a dose of 2.5 mg L^?1 of CRP (0.225 mg L^?1 rotenone) for pond application.