Field and laboratory characterization of rotenone attenuation in eight lakes of the Kenai Peninsula, Alaska.

Rotenone is a pesticide commonly used to eradicate Northern Pike (Esox lucius), an invasive species, in Southcentral Alaska. The present work incorporates a field investigation of rotenone attenuation in eight lakes of the Kenai Peninsula, following a CFT Legumine® treatment in October 2018 and a laboratory simulation to determine persistence under light/dark and sterile/nonsterile conditions representative of Southcentral Alaskan winters. In the field, rotenone degraded within <60 days of application in all lakes, while rotenolone, the primary product of rotenone degradation, persisted for up to <280 days post-treatment at two locations. Prolonged rotenolone attenuation was most likely caused by short days and ice cover between October and April. This hypothesis was supported by a laboratory simulation which revealed photolysis as the dominant process driving the overall degradation of rotenone and that microbial degradation will significantly contribute in the absence of sunlight under simulated "winter" conditions of 4 °C. Degradation model fit comparisons (pseudo-first order, multi-parameter linear, and gamma) indicate the most accurate prediction occurred when modeling all eight lakes grouped together in a single dataset, combined and treated with pseudo-first order model kinetics, based on Akaike information criteria (AIC) scores.