Data presented in folloiving sections indicate that nev:ly- 

 transfonned sea lanpreys migrate dovmstrearn during the late fall, 

 TJinter, and early spring months. Consequently, the age group 

 vAiich these migrants represent rrould be absent from spring col- 

 lections made immediately after the termination of the doimstrean 

 migration. To illustrate the size range of this departing age 

 group, a length-frequency distribution of a random sample of 714-9 

 neiTly-transformed, dovaistream mignr-ants is interpolated in Figure 55. 

 These migrant juveniles -were tal-cen in the Ocqueoc River betvreen 

 November 1, 19h5, and llarch 20, 19h9', they ranged from 111 to 193 

 millimeters and averaged I36.U millimeters in total length. Young- 

 of-the-year (age group O) would likeivise be absent since spaivning 

 ivould not yet have occurred. Further, if age-groups and I of 

 the preceding year are identifiable as age-groups I and II of this 

 new calendar year of grorrth, the existence of additional age- 

 groups may be more readily determined. 



The third large collection, made in Hay, 19U8, revealed a 

 continuous length-frequency distribution (Figure 55 ai:id Appendix K, 

 Table 1). A pronounced size group from 23.0 to ii.3.0 (?) milli- 

 meters (mode: 31 mm..) clearly represents the new age-group I (age- 

 group of the preceding year). Quite distinct from this size 

 group of "yearlings" is a second, som.ei-Aiat binodal hump {h3''0 to 

 83 oO (?) miA. ) in the curve which is judged to represent the new 

 age-group II (I of preceding year). A third hump in the cxirve 

 bearing no distinct mode completes the distribution (83. (?) to 

 171,0 I'm.). 



If the presence of age-groups I and II in the llay collection 

 is accepted at the size ranges indicated (23.0 to i(.3.0 nii. and 

 I4.30O to 83.0 mm.) and the range (111.0 to 193 mm.) and mean size 

 (136. 1; mn.) of the most recently departed age group is considered, 

 it seems unlikely that more than one additional age group, age 

 group III, is present in this series. 



No allowance was made in examining the length-frequency poly- 

 gons for any sexual dimorphism in length which might create a 

 bi-modality in the size class co:.iprising a given age group; none 

 v.ras present among the advilts studied, hence, it was presumed that 

 none Tirould be present among the larvae. 



Based solely on these interpretations of tlie length frequency 

 distributions, I propose that only three age-groups (l-IIl) are 

 tj'picallj'" represented in the spring months. Folloiving the annual 

 addition of young-of-the-year, four groiips (O-IIl) are present 

 until the downstream migration of the oldest and transformed age 

 group begins late in the following fall, lly estimates of the 

 length of the larval life are based on thj.s evaluation of the 

 data. 



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