Experimental control of sea lampreys with electricity on the south shore of Lake Superior, 1953-60

Abstract

Experimental control of the sea lamprey, Petromyzon marinus, with electric barriers was begun in Lake Superior in 1953. Electrical devices were the most practical and promising method of control then available. Installed below spawning grounds in streams and rivers tributary to Lake Superior, these barriers were designed to prevent the sexually mature sea lampreys from reproducing. The catch of sea lampreys at the electric barriers increased rapidly from 1,668 in 1953 to 66,931 in 1958. The total catches dropped substantially in 1959 and 1960 to 52,173 and 39,783, respectively. Electric fields of sufficient intensity to block sea lampreys were potentially lethal to other fish and caused undesirable mortality. Improvements in design and installation, and the development of a direct-current diversion device reduced the mortality and increased the efficiency of operation. The development of control by selective chemicals in 1958 superseded the barrier control system which was terminated at the end of the 1960 season. The electric barrier operation provided considerable information on mature sea lampreys, including data on time of migration, length, weight, and sex composition. Electric devices of the type and design used are capable of blocking entire runs of adult sea lampreys. An accurate appraisal of the effectiveness of the barrier system is impossible, however. Most of the barriers were not operated long enough to reduce the contribution of parasites from the streams. Furthermore, a complete system of efficient electric barriers was never realized. The greatest weakness of this method of control lies in maintenance of the units in continuous, uninterrupted operation through consecutive migratory seasons.