Rotenone in Fisheries: Are the Rewards Worth the Risks?

5. Chemical Residues in Surface and Ground Waters Following Rotenone Application to California Lakes and Streams

Brian J. Finlayson, S. Siepmann, and J. Trumbo

doi: https://doi.org/10.47886/9781888569339.ch5

Abstract.—Over the past 15 years, the California Department of Fish and Game has monitored applications of the rotenone formulations Nusyn-Noxfish^® (synergized liquid formulation) and Pro-Noxfish^® (powdered formulation) to lakes and streams. The monitoring studies were designed to limit liability and address environmental and public health issues. Results indicated that (a) the half-life (t_½) of rotenone increased inversely with temperature from 0.6 to 7.7 days; (b) the degradation product rotenolone was generally not found in the absence of rotenone, except in waters of low alkalinity (<15 mg/L CaCO₃) and temperature (<11°C); (c) Nusyn-Noxfish® contaminant trichloroethylene (up to 4.9 μg/L) and additive xylene (up to 6.7 μg/L) were found typically only in lakes; (d) Nusyn-Noxfish® additives naphthalene (up to 332 μg/L) and methylnaphthalenes (up to 390 μg/L) were found in both lakes and streams; (e) potassium permanganate can neutralize rotenone within a contact time of 30 minutes; (f) Nusyn-Noxfish® synergist piperonyl butoxide can persist in cold (<10°C) and deep (>25 m) waters for up to nine months; and (g) ground water remained free of chemicals in both rotenone formulations. These studies demonstrated that (a) toxicity and other effects can be confined to the treatment and neutralization areas; (b) concentrations of chemicals in surface waters (with the exception of rotenolone and piperonyl butoxide in cold waters) persist for less than seven weeks; (c) rotenone, naphthalene, and methylnaphthalene persist in sediments for short periods; and (d) ground waters were not contaminated.