methods in the field- -are in fact but parts of a 

 single vast experiment in the reduction of a 

 widespread and highly destructive population of 

 parasites. 



Research on the sea lamprey 



At the time the sea lamprey program 

 was expanded in 1950, the fundamentals of the 

 natural history of that parasite had been made 

 known through the graduate researches at the 

 University of Michigan of Vernon C . Applegate, 

 an employee of the Michigan Department of Con- 

 servation. Indeed, it was his broad experience 

 and demonstrated competence in this field that 

 led to his selection as Director of the Hammond 

 Bay Fishery Laboratory. The newly established 

 field station at once set about to continue and ex- 

 pand those portions of studies on which Apple - 

 gate's findings were incomplete and to undertake 

 new lines of investigation that previously had not 

 been possible. Results of most of this work 

 have been so well documented that only brief ac- 

 counts of them need be made here. 



Ecology of the sea lamprey. - - Much ad- 

 ditional information on the sea lamprey was 

 obtained in the operation of various control de- 

 vices where data were accumulated in such 

 matters as; time and factors (temperature, 

 water flow, , . .) of migration of sea lampreys 

 and associated migratory fish species: duration 

 of runs; characteristics of sea lamprey spawn- 

 ing runs- -length, weight, sex ratio in various 

 periods of the run; kinds of streams utilized by 

 lampreys. The inclined-screen -and-trap barri- 

 er in the Carp Lake River (tributary to the 

 Straits of Mackinaw) has yielded data on sea 

 lampreys recently transformed from the ammo- 

 cete to the parasitic state --size, numbers 

 produced annually, time and factors of down- 

 stream movement, length of larval life. The ob- 

 servations at barriers are being continued; 

 particularly detailed records are maintained for 

 tributaries chosen as "index" streams. 



Movements of parasitic -phase lampreys 

 tagged in the open lake indicated little or no hom- 

 ing tendency. Many of these lampreys were 

 obtained for tagging in the course of experiment- 

 al fishing operations carried out to study fish- 

 lamprey relations in northern Lake Huron- - 

 abundance of lampreys and various species of 



fish, incidence of sea lamprey scars in relation 

 to host species, size of fish, locality, and 

 season. 



A series of stream surveys designed to 

 show the "lamprey potentials" of the various 

 tributaries of the upper lakes has given a large 

 amount of information on such points as: volume 

 and rate of flow; temperatures and chemical 

 characteristics of the water; natural and man- 

 made barriers; extent of grounds suitable for 

 lamprey spawning; extent of larval habitat . It 

 is anticipated that these records will lead to a 

 better understanding of the lamprey's selection 

 of certain streams and its failure to spawn in 

 others. 



Laboratory studies of the development, 

 growth, and feeding. --An early project at the 

 Hammond Bay Laboratory was the rearing of 

 parasitic -phase sea lamprey from the recently 

 transformed stage to full sexual maturity. These 

 experiments verified the earlier estimate (based 

 on measurements of lake -caught lampreys) that 

 the parasitic phase lasts 12 to 18 months; only 

 exceptionally (under conditions of poor growth) 

 may an additional year be required. Lampreys 

 reared to maturity in the laboratory consumed, 

 on the average, 18 .5 pounds of fish each. Since 

 they reached only half the weight of "wild" lam- 

 preys, the average kill of fish in the lakes may 

 be twice as great. 



Observations made during the course of 

 the laboratory rearing of parasitic -phase sea 

 lampreys formed the basis of a doctoral disserta- 

 tion (University of Michigan) by Lennon on the 

 feeding mechanism and its effect on host fishes. 

 Major aspects of this study were: anatomy of the 

 feeding mechanism; physiological effects of 

 buccal-gland sections on host fish; mechanics of 

 attachment and distribution and gross pathology 

 of wounds; cause of death of host fish. Lennon 

 also succeeded in the artificial fertilization of 

 sea lamprey eggs and reared the young through 

 21 weeks. 



Still another doctoral dissertation (Duke 

 University) was Piavis' descriptive and experi- 

 mental study of the embryology of the sea lamprey. 

 An important contribution of this research to the 

 control program was the establishment of the 

 rather narrow temperature limits within which 



