greatest movement, in late March and early April occurred during 

 rising water temperatures and almost entirely at daily means 

 below hi degrees F. (Figures 61-62 and Appendix I, Tables 1 and 

 2). There is no eirldent relationship between fluctuations in 

 water temperature and the amount of migratory activity in any 

 season. Furthermore, I do not believe that mean temperature levels 

 belov; 1;1 degrees F. are a critical factor influencing the doim- 

 stream movement. It appears, rather, that such temperatures are 

 coincidental mth that season iThen the lampreys have attained full 

 transformation and are ready to move downstream. All evidence 

 accumulated thus far indicates that the stimulus for this m.ovement 

 is primarily provided by sudden increases in the stream's volume 

 cf flow. 



Length com-position of downstream runs , and 



weight of doimstream migrants 



All of the recently-transformed sea lampreys taken on every 

 other day in botli rivers were measured for total length; some ad- 

 ditional samples were also measured. This dimension was taken to 

 the nearest millmeter on a measuring board. In all, 2,Ii32 indi- 

 viduals from the Carp Lalce River and 7h9 specimens from the Ocqueoc 

 River were examined. Fully-transformed downstream migrants from 

 the Ocqueoc River ranged from 111 to 193 millimeters in length 

 and averaged 136,Ij. millimeters (o^ equals 11.5 mm.) (I4..3 to 7.6 

 inches; meaning ^oij. inches); those from Carp Lalce River ranged from. 

 95 to 189 millimeters and averaged ll|.3.6 millimeters ("s^^ equals 10.8 mm.) 

 (3.7 to 7.1t inches; mean-5.7 inches). An examination of the length 

 composition of each entire sample indicates a uni-mcdal distribution 

 of lengths, and, for the Carp Lslce River sample lAtiich was the most 

 comprehensive of the two, the frequency polygon is quite sjmmetrical; 

 that for the Ocqueoc River is skewed somewhat to the left. There is 

 no indication of any sexual dimorphism in length at this phase of 

 the life cycle insofar as it mi^t be e:cpressed in a bi-modality, or 

 in an irregular "flattening", of the length-frequency polygons 

 (these data for the Ocqueoc .River sea lampreys are interpolated in 

 Figure ^$; those for the Carp Lake River are presented in Figure 63; 

 combined data incorporated in Appendix I, Table 3). 



The difference in average length (and conformity of length- 

 frequency polygons) of the two samples is attributed to a differ- 

 ential migration by size during the period of downstream movement. 

 The smallest individuals came downstream in the fall. A general in- 

 crease occurred in the average total length of the samples taken 

 during the winter months. These average lengths ivere greatest, as 

 a rule, during the late winter and in the early spring when the peak 

 migratory activity occurred (Appendix I, Table 1) . No collections 

 of the major doiwistream movament in the Ocqueoc River (in the spring) 

 were obtained. I attribute the lesser average leng^th of specimens 

 from this river and the asymmetry (left skewness) of the length- 

 frequency polygon for the total collection (Figure 55) to the absence 

 cf such samples, 



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