Figure 55. Length-frequency distributions of collections of am- 

 mocoetes made in the Ocqueoc River in August, 19U7« 

 and May, 19hQ' A frequency polygon of the lengths of 

 a random sample of 7^49 newly-transformed individuals 

 taken in that river betiveen Nov» 1_, 19hQ, and March 

 20, 19h9} is interpolated for comparison. o .. „ 150 



Figure 56. Minimum, average, and maximum length of young-of- 

 the-year sea lamprey ammocoetes collected at 

 intervals during their first season of grotvtho „ „ = ,. « a » . o l5l 



Figure 5?. Ocqueoc River sea lamprey weir and traps. Lateral 

 view showing f ine-^nesh screens in place for 

 trapping downstream migrants. February^, 19U9» <.«»<..... . 155 



Figure 58. Ocqueoc River sea lamprey -weir and traps during 

 operation in winter months „ February, 19U9>. 

 (View from downstream) ..._.. o .„, o . l56 



Figure $9- Carp Lake River dam and inclined-screen trap in 



operation during warmer months . June, 19U8 . . . . . . . , . . . . 157 



Figure 60. Carp Lake River dam and inclined-screen trap in 

 operation during winter months. Trap-box has 

 been removed and replaced by a baffle across the 

 foot of the inclined screen. February, 19U9. ......... • l59 



Figure 61. Numbers of recently-transfonaed sea lampreys migrating 

 downstream in the Ocqueoc River between October 2U, 

 19U8, and March 20, 19li9, with water gauge readings, 

 daily mean and range of water temperature, and mean 

 daily air temperature for the period. « o...,. .......... . l6l 



Figure 62. Numbers of recently-transformed sea la m preys 

 migrating downstream in the Carp I^ike River 

 between October 1, 19U8 and April 30^, 19h9, "vifith 

 water gauge readings, daily mean and range cf 

 Tfater temperature, and mean daily air tempera- 

 ture for the period. .„...„. ..o...... o. ...o,. ...„.....«•. 162 



Figure 63. Length-frequency distribution of 2,li82 recently- 

 transformed sea lampreys taken during their dovm- 

 stream migration in the Carp Lake River in the 



Figure 6U. Distribution map of llU collections of parasitic 

 sea lampreys taken in Lake Huron and its northern 

 connecting waters ...„,.... ^ ..>.....,.................. . 170 



Figure 65. Size composition of collections of parasitic sea 

 lampreys taken from the Great Lakes in different 

 months of the year in relation to the size composition 

 and periods of migration of newly-transformed indivi- 

 duals and sexually mature sea lampreys ................. 173 



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