Determination of a desirable concentration of 5 percent emulsified rotenone in. a given lake to control gizzard shad was accomplished by an observational technique. The concentration employed varied from 0.06 p.p.m. to 0.14 p.p.m. The time of year considered best suited for treatment was during the fall. Methods used to apply the toxicant were varied but appeared about equal of results except while using spray planes. The most favorable results occurred when good distribution was secured by using six to twelve hours for application, numerous surface units and dilute mixtures. As many as 4,600 acre feet were treated by one efficiently equipped boat. A table is presented which was used as a basis for calculations of concentrations. At least three successive treatments one year apart were needed for the most effective control of shad. Conclusions regarding stocking were not drawn.
