sudden surge of migrants appeared (3,h67 individuals betvteen night- 

 fall and daylight). Subsiding ivater levels were acconpanied by 

 a decline in downstream migration until December 9- From this date 

 until March 22, 19h9, domistreaTi movement was of a minor nature al- 

 though, as in the Ocqueoc River, at least a few individuals came 

 do'vvnstream on nearly every day during the interval. Between Jan- 

 uary 17 and 2k, cold rains increased the volume of flow in the 

 river. Most of this water was passed do\vnstrdam on top of the ice 

 which had covered nearly all of the river since mid-December. A 

 similar condition prevailed between Febmaarj'" 23 and 2? as a result 

 of snow, sleet, rains, and a light thaw. Both of these brief in- 

 creases in volume of flow were accompanied by spurts of doTmstream 

 migratory activity (Figure 62 and Appendix I, Table 2). 



Warm, thav/ing winds in the Carp Lake region from March 20 to 

 2$ precipitated the spring break-up and severe flood conditions 

 v/ere created in the watershed as snow and ice melted rapidly. 

 Water levels rose abruptly on March 22. On the same date and ac- 

 companying these conditions, the major downstream movement of 

 lampreys began (Figure 62). On March 26, the water overtopped the 

 dam and undercut one wing; the trap box was also destroyed. The 

 structure was not restored to full operating efficiency until 

 April 13. During the period March 26-April 3, a very great number 

 of do'vvnstream migrants v/as observed passing over the dam during 

 the daylight hours j migrants were most numerous between March 26 

 and 30. Some measure 01 the large size of this movement may be 

 deduced from the follovri.ng incident. A small, dead space (air 

 space) existed between the lip of the spillway, the edge of the 

 inclined screen, and the closest point ■viiiere the spilled water 

 struck the screen. This space, triangular in cross section, had 

 a base on the screen about 5 inches wide. On March 26, 2k hours 

 after the flood over-topped the dam, access was gained to a 30- 

 inch length of this air space. We removed 61); sea lampreys from 

 this limited area. It was also determined visually that an equiva- 

 lent concentration was trapped beneath the entire lip of the spill- 

 vray. It is estimated, therefore, that between 3^000 and L|.,000 

 migrants had accumulated in this small air pocket in the first 2k 

 hours after the trap had been rendered inoperative. 



A few migrants were observed passing downstream during day- 

 light hours between April 3 and 10; thereafter, none were seen. 

 Yiiater levels declined during this period and on April 13, when the 

 trap -vras again operative, they had receded to about mean spring 

 levels. Between April 19 and 23, seven individuals came downstream, 

 j'roia the latter date until June 30, when these records terminate, 

 no others appeared. 



In both riversj the initial surge of downstream movement in 

 November occurred during declining water temperatures and when the 

 latter were generally at daily means of Ul degrees F. or lower. 

 Midwinter increases in migration occurred at water temperatures 

 which were stabilized at, or very close to, 32.0 degrees F. The 



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