Since the inauguration of the sea-lamprey investigations as a 



part of the Ser^Jioe 's Great Lakes Fishery Investigations, in October 

 I9I1.9, consic.erabi'^. prcgr'e-rss has been made axi the long-term prcgr*am 

 for the d.evelc.pmer_t of methods of suppi'esof-ng or controlling the 

 pai-asitie sea lamprey. The sea-lamprey investigations may be divided 

 broadly into the folloiving phases: development and testing of con- 

 trol devices and procedirr-es, inelioding the acc-umulation of reasonably 

 exact data on costs of iD.stallation and operation of various struc- 

 tiiresj exir-ension cf studies on the life history and habits of the sea 

 lampi'ey -with a view tovra^d detei-mining better the vulnerable stages 

 of tiie life histo:cyj sunreys of streams to ascertain the distribution 

 of sea-lamprey runs and the extent of available spamiing grounds; and, 

 studies of species subject to attacks hj sea lampreys to learn the 

 incidence of attacks and the effects on abxmdance. 



Selected from the pre:;ed±ng investigative program for inclusion 

 herein az'e summarizations of data collected in 19^1 concerning: a 

 second yeai' of experimental control operations in Control Zone H-1 

 (in nort.hem Lak:e H\iron) and in the Wisconsin -maters of Lake Michiganj 

 abundaiice of sea lampreys in the thi-ee upper lakes; a comparison of 

 the biological chai'acteristics of the sea-lamprey spatvning runs of 

 19>1 with these of pi'evious years; and developments and further eval- 

 uation of mechanical de'/ices for sea-lamprey control. 



Similar data for the 19^0 season ar.d information basic to this 

 report have been presented by Applegate and Smith (19^1). 



These particular operations and investigations were conducted as 

 in the previous year, W3.th the cooperation of the Wisconsin Conserva- 

 tion Departmenb and the Michigan Department of Conservation. 



Installation and operation of sea-lamprey-control structures in 19^1 



Lake Huron . — In nort-hera Lake Ku-ron 12 trapping devices "vvere 

 operatea in," Conti-ol Zone H-1 "srfiich was established in 19^0; 11 of 

 these sti-uctui-es were operated in the same streams as in the previous 

 year* (Applegate and Smith, 1951). In addition, a trap was installed 

 in the bottom compartment of the fish ladder at the paper-mill power 

 dam on the Cheboygan. River (fig. 1). All installations were the stan- 

 dard, po;rtable-type sea-lamprey weir and traps with the exception of 

 the pe:o.nanent"type Ocqueoc Ri.ver installation and the aforementioned 

 Cheboygan River trap which ivas a de-'rlce manufactured especially to 

 fib a fish-ladder Gompar-'&ment. Complete runs were captured in all but 

 tvro streams, and in one of these only a minor escapement occurred. In 

 the Cheboygan River only a small part of the -bobal run was taken be-, 

 cause the trap could n.)t be located near the main spill of the water 

 and consequently the majority of the lampreys were attracted away from 

 the trap. However j the dam prevented the upstream movement cf the 

 lampreys not taksn by the trap. 



