John Wiley & Sons, Ltd.

Fate and behavior of rotenone in Diamond Lake, Oregon following invasive tui chub eradication

In September 2006, Diamond Lake was treated by the Oregon Department of Fish and Wildlife with a mixture of powdered and liquid rotenone in the successful eradication of invasive tui chub Gila bicolor. During treatment, the lake was in the middle of a phytoplankton (including cyanobacteria Anabaena sp.) bloom, resulting in an elevated pH of 9.7. Dissipation of rotenone and its major metabolite rotenolone from water, sediment and macrophytes were monitored. Rotenone dissipated quickly from Diamond Lake water; about 75% was gone within 2 d, and the average half‐life (t½) value, estimated using first‐order kinetics, was 4.5 d. Rotenolone persisted longer (>46 d) with a short‐term t½ value of 16.2 d. Neither compound was found in groundwater, sediments or macrophytes. The dissipation of rotenone and rotenolone appeared to occur in two stages, possibly caused by a release of both compounds from decaying phytoplankton following their initial dissipation. Fisheries managers applying rotenone for fish eradication in lentic environments should consider the following to maximize efficacy and regulatory compliance: (1) treat at a minimum of twice the minimum dose demonstrated for complete mortality of the target species and possibly higher depending on the site's water pH and algae abundance and (2) implement a program that closely monitors rotenone concentrations in the post‐treatment management of a treated water body. Environ Toxicol Chem © 2014 SETAC

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