and 3:00 A. - ., 33.2 to 33,0 psrcent sntsred the trap betrreen 6:00 

 P. '-.'.. and 12:00 P. I.':. Tihils 60.1 to 66. 1| percent were taJ-cen 'betT.'een 

 that latter hour and 3:00 A. I.'. Tine of rr-i^ration into the Ocqueoc 

 River, a larger strear., was almost the sane. In that stream in 19h9} 

 0,8 percent oi the run entered the traps during full daylight, 32,7 

 percent betvreen 6:00 P, I.;, and 12:00 P. I,',, and 66,5 percent betvreen 

 12:00 P. :>'. ana 3:00 A. :.', This agrees e's-f^rally mth Shetter's 

 data (19U?) on the Ocqueoc River for which he noted th^at !?!? percent 

 of the r^an occurred between the hours of midnight and 6:00 A. V., 



Only slight, and probably not significant, differences were 

 displayed in the time of migration of the two S3::es in all runs 

 studied. I'or exanple, of all males taken in Carp Creek in 19h.9, 

 0,3 percent entered the trap during full daylight (prior to 6:00 

 P. i-'.), 3p.9 percent between 6:00 P. M. and 12:00 P. L., and 63.2 

 percent betvraen 12:00 P, L, and 3:00 A, IvI, Of all feraales taken, 

 1,0 percent entered the trap during the hours of full daylight, 

 3U.0 percent between 6:00 P. i:. and 12:00 P. LI, and 6>,0 percent 

 betvreen 12:00 P. I.I. and 3:00 A. I'., 



Changes may occur in most runs in the daily time of migration 

 during the course of the run. The Carp Creek run in 19U7 may be 

 cited as an -e^iajr.ple. Until L'ay 29, no sea lampreys entered the 

 trap except during the hours of full darlmoss. r-orthermore, during 

 this same period, the buHc of the upstream m.ovement occui-red between 

 the hoiirs of midnight and 8:00 A. I'.. After the end of I.Iay, sea lam- 

 preys began to appear in the trap during the daylight hours and an 

 increasing number entered during the earlier hours of the evening. 

 If we breaJc dorm the data for the period April 2l4-June 21, 19U7, 

 into two arbitrary periods we find that the folloiTing occurred: Of 

 393 sea lampreys taken in the trap between April 2U and Kay 31, only 

 1 or 0.1 percent entered during the hours of full daylight (prior to 

 6:00 P. I.:,), 265^ or 29.5 percent betvreen 6:00 and 12:00 P. ::., and 

 632 or 70. li percent between the latter hour and 8:00 A. L, Betvreen 

 June 1 and June 21, 623 sea lanpreys were trapped. Of these, 23 or 

 I4..5 percent moved into the trap during daylight hours (prior to 

 6:00 P, L!.), 313 or 50.2 percent entered between 6:00 and 12:00 P. I.:,, 

 and 232 or U5.3 percent entered between midnight and 8:00 A. I:. 



EoT/ever, this shift in tim.s of m.igration was not repeated in this 

 stream in 19h9« The run of this year displayed a proportionate in- 

 crease in migratory activity in tlie latter half of the season beti,7een 

 th.e hours of midnight and 3:00 A. i:, 



Field observations during 19h7 and 19U3 revealed tliat, at the 

 beginning of the spawning run, sea lamvreys displayed a ver;>" strong 

 negative response to light. This response becomes less and less 

 pronounced among later arrivals as the season prog-resses. The data 

 from, the Carp Creek and Ocnueoc River weirs are conf irriatory, A 1 

 variation of this v/as shov,-:! by Shetter (19U9) for the Ocqueoc River 

 run in 19U5. Re found a somewhat greater proportion of migrants 



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