sea lampreys are able to undergo normal 

 development. 



Support of research in other institu- 

 tions. --Financial and technical assistance by 

 Great Lakes Fishery Investigations made pos- 

 sible two additional doctoral studies: Wigley 

 (Cornell University) on the life history of the 

 sea lamprey in Cayuga Lake, New York; Sawyer 

 (University of Michigan) on the physiological 

 effects of various toxicants on sea lamprey 

 larvae. The Hammond Bay laboratory has also 

 supplied extensive materials for research by 

 various institutions and individuals on a number 

 of physiological and morphological problems. 

 In the course of this cooperation, methods 

 were developed for transporting live sea lam- 

 preys over great distances. 



Development of control methods . 



Mechanical barriers. -- The major de- 

 vices tested for blocking or capturing spawning- 

 run sea lampreys were: permanent weirs with 

 removable screens and traps; "demountable" 

 weirs of hardware cloth on wooden frames; 

 barrier dams that cannot be scaled by lampreys 

 because of a retrocurve lip. In addition, ' a 

 dam with an inclined-screen trap was tested as 

 a means of capturing recently transformed 

 downstream migrants. The principal benefits 

 from these tests were the information gained 

 on sea lampreys and associated fishes and the 

 clear demonstration that lampreys were not to 

 be controlled by mechanical procedures. The 

 weirs and the inclined-screen trap commonly 

 failed in periods of flood (some structures were 

 entirely washed out). Even when weirs could 

 be held the cost of maintenance and operation 

 was excessive. The barrier dam proved ef- 

 fective but its use is limited to the few streams 

 in which it does not cause undue flooding. 



Electrical barriers . - -The unsatisfactory 

 experiences with mechanical devices led to a 

 start on experimentation with electricity in 1951. 

 In order that the program might be technically 

 sound and efficiently operated, a contract for 

 engineering assistance was negotiated with the 

 Cook Research Laboratories. This laboratory 

 supplied the services first of William A. Stahl 

 and later of Willis L . Nielsen; it also conducted 

 patent searches on uses of electricity for taking. 



killing, or controlling the movements of 

 fish. 



Preliminary experimentation led to the 

 abandonment of electricity as a means of destroy- 

 ing larval lampreys in streambeds or of killing 

 recently transformed lampreys on their down- 

 stream migration . Larvae could be driven 

 from the stream bottom by electric shockers 

 but only a fraction left the burrows and few were 

 killed. The resistance of downstream migrants 

 to electricity proved so great that power costs 

 alone would have prevented their destruction by 

 this means even had the engineering problems 

 been solved. 



The early experiments in leading fish 

 with electricity revealed the appropriate wave 

 form and duty cycles, but also uncovered dif- 

 ficulties arising from differences in the reactions 

 of fish of various sizes and species. Experi- 

 mentation with direct current was accordingly 

 abandoned temporarily in favor of the work with 

 alternating current. Studies with direct current 

 were resumed in 1955 in an attempt to reduce 

 the kill of useful fish at certain of the alternating- 

 current barriers in tributaries of Lake Superior . 

 This more recent work has led to the develop- 

 ment of equipment in which the direct current is 

 used to repel fish, not to lead them; a cathode 

 array in the stream turns the fish away from the 

 water in which they might be killed by the alter- 

 nating current. Field tests indicate that this 

 new equipment will put an end to the formerly 

 troublesome fish kills and ultimately may be de- 

 veloped to the point that it can be substituted for 

 alternating-current barriers. 



The sea lamprey control program at 

 present is based almost entirely on the blocking 

 of the spawning run with barriers energized with 

 110 -volt alternating current. Shielded traps are 

 constructed along with the barriers to take use- 

 ful fish which are passed safely upstream . 

 Experimentation on the flow of electricity in 

 water of different electrolytic content (including 

 the development and patenting of a "probe" for 

 measuring voltage gradients) and extensive field 

 testing of electrode arrangements led to thethree 

 types of barriers now in use; parallel arrays of 

 suspended pipe electrodes; single array of sus- 

 pended pipe electrodes and ground electrodes in 

 the stream bottom; two parallel ground electrodes 



