Determination of Minimum Lethal Level of Toxaphene As A Piscicide in Lakes of North Dakota

Toxaphene as a piscicide for localized field application has not been widely used because minimum lethal concentrations have not been in the field. There is, however, considerable information gained from laboratory bio-assay studies (Surber, 1498; Duedoreff, et al. 1953; Hooper and Grzenda, 1955, et al. 1959). Concentrations indicated by such studies are not necessarily correct for field use. Prevost (1960) pointed out that results from controlled laboratory experiments do not always yield dosages exhibiting similar results in the field where a number of variables, both known and unknown, exist over which the field worker has little or no control. Gebhards (1960) in a review of toxaphene as a fish toxicant lists 14 western states and 6 Canadian provinces that have used toxaphene in fish control programs. Toxaphene was used in various formulations at concentrations ranging from a low of 0.003 parts per million (p.p.m) to a high of 0.61 p.p.m. Complete kills were variable in their occurrence within this range. Inconsistencies were emphasized in the review by the wide variations in results. An Average concentration of 0.135 p.p.m. from 15 reports failed to kill all fishes in treated areas but an average concentration of 0.139 p.p.m. from 23 reports induced complete mortalities. Stringer and NoHynn (1953), however, reported complete kills at from 0.010 p.p.m. to 0.036 p.p.m. In North Dakota complete fish population mortality occurred when toxaphene was applied at a concentration of 0.070 p.p.m. (Henegar, 1958) which was not considered as the minimum lethal level. It was to determine the desirable minimum concentration for management use in North Dakota that this study was initiated. Sixteen lakes were chosen for treatment during 1959 and 1960. All lakes were test netted to determine existing populations of fishes both before and after treatment. Physical and chemical characteristics were studied to establish criteria. Application of the toxaphene followed procedures commonly used by the North Dakota Game and Fish Department. In lakes displaying similar physical and chemical characteristics to those in the Great Plains area, recommended concentrations range from 0.025 to 0.030 p.p.m. as indicated in Table 1. Concentrations used on the project areas ranged from 0.005 to 0.035 p.p.m