The Results of Four Years of Fish eradication Work with Toxaphene in Nebraska

Experimental use of the compound, toxaphene, (chlorinated camphene), as a fish eradicant was first tried in Nebraska during 1956. During the period from 1956 to 1958 a total of 3,810 acres of water have been treated with emulsifiable toxaphene to remove rough fish populations. Concentration levels ranged from 0.05 p.p.m., to 0.61 p.p.m. The maximum depth of the nine renovated sandhill lakes was seven feet with an average depth of only 4.5 feet. Numerous spring seeps are found in all lakes and bottom deposits were organic muck and sand. The lakes are considered moderately alkaline in the 8.5 - 9.5 p.H range. Lake waters were for the most part turbid during the periods of application. A brief discussion of the toxaphene results on nine sandhill lakes will be covered in this paper. A summary of the 1956-1959 toxaphene activities in Nebraska appears in Table Ill. U. S. Fish and Wildlife Service personnel originated and programmed the first dispersal of this toxicant on a Federal Wildlife Refuge lake in the spring of 1956. The Nebraska Game, Forestation and Parks Commission, actively seeking an economical and efficient fish toxicant, also became interested in toxaphene at this time, and thus a federal-state cooperative refuge lake rehabilitation project became a reality. The problem fish in all refuge lakes was the carp, while the black bullhead was the secondary target of control. Following the incomplete fish kills experienced during the initial eradication efforts in 1956, fisheries workers from the Service and Nebraska concluded that toxaphene dosages of 0.12 to 0.15 p.p.m. were not sufficient for complete kills of carp and bullhead in the sandhill region. A review of the available literature from other states indicated a great diversity of findings regarding the field use of toxaphene. Those states which were experimenting with this toxicant suggested dosage levels from 0.01 to 0.2 p.p.m.; however, none reported treatment on lakes which contained chemical, physical or biological characteristics of the alkaline fertile waters in the Great Plains area. It was decided to continue toxaphene applications in 1957, but with a minimum dosage of 0.40 p.p.m