prey entered a weir-trap on Septer;ber 2U. 



A total of 2li,6l43 sea lanpreys T<-as tal:en in the Ocqueoc River 

 weir in 19U9. 



In general, the Ocqueoc River sea lair.prey run resenbled the 

 runs occurring in Carp Creek in 191+0 and 19U9 insofar as large up- 

 surges of migratory activity occurred during periods of particularly 

 T/arm weather. The initial "surge" was accentuated, of course, by 

 the large stock of ter.porarily blockaded lanpreys below the weir 

 which suddenly began to r.ove upstream. 



The Ocqueoc River run differed nost noticeably from the runs in 

 Carp Creek in its more continuous character. Fewer sudden increases 

 and decreases in migrator^' activity from one 2l4.-hour period to the 

 next occurred. Being a considerably larger strear. than Carp Creek, 

 it is less profoundly and zzore slovdy affected by changes in climatic 

 conditions. 



(2) Factors affecting the runs 



There is a very close relationship between water temperature 

 and the amount of migratory activity of the sea lamprey (Figures 

 15-18; Appendix C). It is ver;.'' seldom that any upstream movement 

 occurs at mean daily water temperatures of UO degrees F. or lovrer. 

 Such infrequent activity as does occur is alvrays associated with 

 temperatures verj^ close to the l|0-degree level. Liigratory activity 

 at mean daily temperatures between UO degrees F. and ^0 degrees F. 

 is, as a rule, light and is very sensitive to fluctuations within 

 this range. In general, activity increases as the JO-degree level 

 is approached. The greatest migratory activity occurs at mean 

 temperatures of $0 degrees F, to 65 degrees F. Water temperatures 

 above this optimum range have an inhibiting effect upon the upstream 

 movement (Figiires 15-18 j Appendix C), 



If daily catches of weir-traps are plotted against mean daily 

 water temperatures, a curvi-linear relationship is evident. Both 

 Tdthin and ivithout the optimum range, however, the response in 

 migratorj'" activity is not alvrays proportional to the amount of 

 change in water temperature. On certain occasions, a negative 

 response may occur. These deviations are, in part, attributable 

 to the period during the run in which they occur. During the 

 latter part of the run, evident reactions to temperature fluctua- 

 tions reckoned in numbers of migrants are obviously less than in 

 the early part since the stock of mature individuals in the lalce 

 (from which they are drawn) has been considerably reduced. De- 

 clining migratory activity in a small stream, in the presence of 

 increasingly favorable water temperatures, may also be caused by 

 strong onshore winds at the mouth of the streams. Such iTinds de- 

 flect the creeks' discharge into the zone of ivave action and 

 apparently cause lampreys, searching for a stream in which to spaT.-n, 

 to by-pass the creek. 



-hh- 



