It is logical to assime that some lampreys die before they 

 succeed in finding suitable spaiming grounds. This they may 

 experience in streams^ t^en blocked by a large dam, or in the 

 Great Lakes, when imable to locate an adequate stream. In order 

 to measure the effect of such frustration experimentally, I 

 imprisoned migrants as follows: In 19U7j 50 migrant sea lam- 

 preys (30 males and 20 females) were taken from the Carp Creek 

 weir on May 20 and 2U and on June 1$, and placed in live-crates 

 anchored in Ocqueoc Lake at depths of 2 to U feet. Ten lampreys 

 were placed in each of five comparianents which averaged about 

 1 1/2 cubic yards of space apiece. An equivalent number of 8- 

 to 11-inch black bullheads were placed in each compartment 

 (none of these bullheads were ever attacked by the imprisoned 

 lampreys). The bottoms of three compartments were of planed 

 wood, and of the remaining two, wood covered with a layer of 

 silt and sand. Lake vrater temperatures here varied from $3 

 degrees F. to 75 degrees F. during the course of the experiment. 



Initiallj'', all imprisoned lampreys were very restless and 

 moved about almost continuously searching for a way out of the 

 crate. This restlessness became very pronounced on June 2$, 

 Between then and Jime 28, 12 males and $ females died. Between 

 the latter date and July 3) 9 males and 1^ females likewise died. 

 Of the remainder (all males), two died on or before July 11, six 

 on or before July 18, and the remaining specimen expired on 

 July 25. 



With the exception of the retention of the unspawned eggs or 

 milt, anatomical and degenerative changes among these dead speci- 

 mens were like those in spent sea lampreys. The color of the 

 liver, the degree of reduction of the digestive tract, loss of 

 vision, and sloughing of skin were all similar (subsequent dis- 

 cussions treat in more detail upon these changes among migrant 

 and spawning individuals). 



In this experiment, the specimens were held at higher water 

 temperatures imlike those which normally blocked migrants would 

 have found had they moved back from a barrier structure into 

 the Great Lakes proper. These elevated temperatures probably 

 accelerated the normal rate of mortality or hindered a possible 

 recovery from the anatomical changes accompanying sexual maturity. 

 However, h migrant adults taken from Carp Greek on May 29, 19li7, 

 and held in running water aquaria at the Oden State Fish Hatchery 

 at an average water temperature of k9 degrees F. (range: US to 

 $2 degrees F. ) also died. Either suckers or trout were also 

 placed in the aquaria. 2/ The lampreys were very active for several 

 days, apparently seeking a way out of the tanks. Thereafter, 

 they quieted down and were never active unless disturbed. At no 

 time did they attack either suckers or trout placed with them. 

 Three specimens were killed on June 12, June 28, and August 5, 

 respectively, and examined. Liver color and reduction of the 



8/Experiment conducted and observations by Mr. R. F, Sharkey of 

 the Oden State Fish Hatchery. 



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