SEA LAMPREY OF CAYUGA LAKE 



565 



Figure 3. — Weight composition of Cayuga Lake sea lampreys. (Description of symbols is given in the caption of fig. 1.) 



Table 2. — Summary of weight measurements of sea lampreys 

 captured in Cayuga Inlet 



Annual mean body weights for the sexes com- 

 bined, together with the estimated abundance of 

 lampreys follow. 



1 Refer to p. 578 for details pertaining to population estimates. 



Mean weight for the 1950 sample, shown in 

 parentheses, was based on 245 specimens, which is 

 approximately 2 percent of the estimated number 

 in the spawning migration. Since they were taken 

 during the early part of the migratory period, it is 



believed that this sample is biased in favor of un- 

 usually large specimens. Mean weights for 1951 

 and 1952 represent specimens taken throughout 

 the migratory period, and each year 21 percent of 

 the estimated total number were weighed. 



The mean weight of sea lampreys differed sig- 

 nificantly from year to year. Except for 1950, a 

 biased value, these variations appear to be in- 

 versely related to their abundance. 



No significant difference could be detected be- 

 tween weights of male and female specimens. In 

 the seasons during which representative samples 

 were measured, however, the females were heavier 

 than males. 



During the spring of 1951 a total of 1,968 sea 

 lampreys from Cayuga Inlet were weighed. These 

 data are depicted in figure 4 to illustrate the 

 weight composition of the adult population of 

 Cayuga Lake sea lampreys. 



Growth of Parasitic-Phase Sea Lampreys 



Evidence has been presented by Applegate 

 (1950) that the sea lamprey in Lakes Huron and 

 Michigan spend between 12 and 20 months in the 

 parasitic phase of life in the lakes proper. Apple- 

 gate's conclusion was based on measurements of 

 specimens taken from the lakes throughout a 1K- 

 year period. In the spring the newly transformed 

 lampreys and the large mature individuals that 

 were ready to enter the tributaries for spawning 

 differed markedly in size. After the spawning 



