cf the sea lampreys in northern Lalce Huron. Chances in the size 

 of sea lamprey rims and in the size and degree of scarring of the 

 concomitant sucker runs seem to indicate strongly that the sea 

 lampreys increased in n-umbers during the period 19h7-19h9 • The 

 greatest augmentation appears to have been in the last year of 

 this period O^aj, 19U3-i-ay, 19U9?). Observations rade in the 

 commercial fishery indicate that the sea lar.ipreys are feeding ex- 

 tensively upon the suckers and for this reason they may provide an 

 index of lamprey abundance. FolloTjing is a tabulation of the 

 total sea lamprey runs, total white and redhorse sucker runs, and 

 percentage of scarred suckers for three years in Carp Creek and 

 one year in the Ocqueoc River. Data on the size of sea lamprey runs 

 for the Ocqueoc River in 19h7 and 19^3 are included and are estimates 

 based on counts of nests that were found in the watershed: 



A very decided increase has occurred in the size of the Ocqueoc 

 River spawning run of lamprej-^s in this three-year period, the rate 

 of increase being greatest between the 19U8 and 19U9 spavming sea- 

 sons. The comparative size of the run in Carp Creek in the last two 

 years does not negate this conclusion as the figures would lead one 

 to believe. The flowage in Carp Creek in 19ii9 is estimated to have 

 been at half the volume of tliat occurring in 19li8. A lesser dis- 

 charge would normally result in fevrer lampreys being attracted to 

 the creek as they sought along the lake shore for a spav/ning stream. 

 In spite of this decreased volume of flow, the run 'vms not signifi- 

 cantly different in size than that occurring in 19U8. 



In Carp Creek, tvith the abrupt increase in scarring of suckers 

 in 19li9... came a continuation of tiae rapid decline in the size of the 

 sucker spaiivning runs. Observations in 19li7 and 19U3 indicate that 

 sucker runs in the Ocqueoc River too were much larger in those years 

 than in 19U9. The size of these runs almost certainly reflects the 

 size of the sucker stocks in Lalce Huron proper. Increase in the 



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