Lake Davis, California
In the mid-1990s, invasive northern pike were confirmed in Lake Davis, a 1,200 hectare reservoir in the California's northern Sierra Nevada mountains. State wildlife officials and local residents raised alarm about the impact of northern pike on native trout populations and tourism. Concern was high that the pike would escape the reservoir and become established in fragile river habitats below the impoundment.
State agencies began a campaign of removal, including an unsuccessful 1997 rotenone treatent, to eradicate the pike. In total, 65,000 pike were taken, but all age classes remained present in the reservoir. In 2007, officials decided to try again and conducted a $16 million US enhanced rotenone treatment.
At the time of treatment, the mean depth of the reservoir was 4.8 metres, with a maximum depth of 30 metres. Considered one of the most complex rotenone eradications conducted to date, extensive post-treatment monitoring indicates the effort was successful. The reservoir was quickly reopened to recreational use and is regularly stocked with rainbow trout.
An air boats used to disperse rotenone along the shoreline of Lake Davis in California during a 2007 treatment. Photo Brian Finlayson