or killed 1, 668 sea lampreys (table 1). The 

 traps included in the control structures to 

 protect migrating fish captured the large ma- 

 jority (90.6 percent) of the sea lampreys; the 

 rest were killed by the electrical field. 



Expansion of the pilot project in 1954 re- 

 sulted in almost complete control along the 

 south shore of Lake Superior . Operations 

 began March 19 and ended August 18 . Of the 

 44 Lake Superior streams- -14 of them west 

 of Marquette, Mich. --18 failed to yield lam- 

 preys. The remaining 26 streams produced 

 a total catch of 4, 922 lampreys (tables 2 and 

 3) . Again the major part (86. 9 percent) of 

 the catch was taken from the traps. Of the 26 

 streams, 7 had large sea -lamprey runs that 

 produced 4, 485 lampreys, or 91.1 percent of 

 the total. It is entirely possible that as the 

 sea -lamprey population in Lake Superior in- 

 creases, these more productive streams will 

 develop spawning runs that are too large to be 

 accomodated and the surplus spawners may 

 have to utilize the less suitable streams. 



In anticipation of the extension of controls 

 to Lake Michigan, and to obtain information on 

 the problems to be encountered, 7 electrical 

 devices were operated in streams tributary to 

 northern Green Bay. All 7 streams had sea- 

 lamprey runs. A total of 7, 367 lampreys was 

 taken, of which 89 .2 percent were captured in 

 the traps (tables 2 and 4). The Sturgeon River" 

 produced 55.8 percent of the total catch in the 

 zone. Observations of sea-lamprey behavior 

 in the stream gave evidence that many lampreys 

 were diverted downstream by the electrical 

 field, and that they returned to the lake to find 

 other streams or died without spawning. 



Comparison of the data for the 10 Lake 

 Superior streams that were under control in 

 both years demonstrated that over comparable 

 periods of operation the catch of sea lampreys 

 increased from 1,624 in 1953 to 2,479 in 1954-- 

 a gain of 53 percent. Further evidence of in- 

 crease was observed from the incidence of 



scarring among the large, sexually mature 

 lake trout caught in the commercial fishery 

 at Marquette, Mich. Of 1,073 lake trout 

 (average weight 8 . 1 pounds) examined in 

 early November 1954, 232 (21.6 percent) 

 were scarred. In the same period in 1953, 

 793 lake trout (average weight 8.6 pounds) 

 included 105 (13.2 percent) scarred individu- 

 als. These data indicate an increase in the 

 sea -lamprey population in Lake Superior 

 similar to the increases that took place in 

 Lake Huron and Lake Michigan. If this 

 increase is not halted, the lampreys will 

 destroy the lake -trout fishery of Lake 

 Superior within the next few years. 



The spawning population of sea lam- 

 preys in Lake Superior is not large at 

 present in comparison with populations in 

 Lake Huron and Lake Michigan, but the out- 

 look for the next several years is poor. It 

 is significant that the present controls serve 

 only to prevent the spawning of future gen- 

 erations. The streams already contain 

 several year classes from past spawnings . 

 Control may have been instituted in time to 

 avert extermination of the lake trout, but 

 unless some means is discovered of destroy- 

 ing larval lampreys in the streams a serious 

 decline of lake trout is almost certain. 



Nor has early control been complete. 

 Some upstream escapement occurred in 

 1954 because of a power breakdown on the 

 Two Hearted River, because of flooding of 

 the mechanical weir on the Chocolay River, 

 and because of a late start on the Huron 

 River. Control is believed to have been 

 complete in all other streams with barriers. 

 Extensive checks of streams above the 

 structures failed to reveal signs of sea 

 lampreys or their nests. Surveys of streams 

 in the control area without electrical barriers 

 disclosed only two streams with sea -lamprey 

 runs. The Misery River, v/est of Keweenaw 

 Peninsula, had several lamprey nests. Rock 

 River, with a 5 -foot concrete dam that was 



