Lake Davis Fisheries Management

Lake Davis Fish Tissue Study  

The California Department of Fish and Game and the University of California at Davis Department of Toxicology measured the levels of rotenone formulation compounds in rainbow trout and brown bullhead in Lake Davis after the September 26-27, 2007 rotenone treatment.   Compounds were measured 3, 10, 30 and 212 days after the treatment.  Some brown bullheads survived the treatment, because this species is very tolerant of rotenone, and the levels applied to Lake Davis were not high enough to eradicate them.  Trout, however, were likely eradicated and restocking began in December 2007. 

Each of the five compounds in the rotenone formulation was measured for this study.  All of the compounds are biodegradable and break down over time.  The compounds measured are:  rotenone (the botanical piscicide), rotenolone (a breakdown product of rotenone) diethylene glycol monoethyl ether, methyl pyrrolidone and the ethylene glycols that make up Fennedefo 99.   The last three compounds are mixed with the rotenone to help it mix with the lake water. 

Brown bullheads were collected and tested 3, 10 and 30 days after treatment.  The rotenone and rotenolone was detectable at the part per billion level 30 days after the treatment.  The other three compounds were no longer detectable.   

Both rainbow trout (which had been restocked about 2 months after the treatment) and brown bullhead (which survived the treatment) were collected 212 days after the treatment. None of the compounds from the rotenone treatment were detectable in the fish. 

These results demonstrate that the compounds in the formulation did not bioaccumulate, or collect in fish tissue over time.  Rather, the levels in the fish tissue reflected the concentrations in the lake and were broken down and flushed out until they became non-detectable.

• Summary of Results (PDF)

For further information on this study and the results, please contact the Department of Fish and Game at (530) 832-4068.