SEA LAMPREY OF CAYUGA LAKE 



591 



sea lamprey from Lake Huron tributaries, re- 

 vealed no appreciable size differences of ova from 

 the anterior, middle, and posterior portions. In 

 accordance with the results of Applegate's studies, 

 the method used in calculating; the number of 

 eggs contained in Cayuga Lake specimens was as 

 follows: total body length and weight of the speci- 

 men were measured; the ovary was dissected from 

 the body, weighed, and preserved in 5-percent 

 formalin; at a later date, the ovary was removed 

 from the preservative, drained, and blotted dry 

 as possible; the entire ovary was weighed to the 

 nearest 0.01 gram; a small portion (1.00-1.55 

 grams) from the midsection of the ovary was re- 

 moved and weighed to the nearest 0.01 gram; the 

 total number of eggs in the sample was counted 

 and the number of eggs in the entire ovary was 

 computed. 



Determinations of fecundity were made for 29 

 sea lampreys collected in Cayuga Inlet on April 30, 

 1951. The size of each specimen and the number 

 of eggs each contained are listed in table 32. 



These lampreys averaged 15.6 inches in length; 

 minimum and maximum lengths, 11.7 and 20.1 

 inches; total body weight averaged 5.1 ounces; and 

 weight extremes were 1.8 and 11.7 ounces. None 

 of the lampreys had deposited any eggs prior to 

 capture, since spawning did not take place until 1 

 month after they were collected. The regression 

 of number of eggs on the total length of lamprey 

 is presented in figure 15. The regression line was 

 fitted mathematically. Extreme egg counts among 

 the specimens were 14,000 and 85,000. 



Average length of female lampreys in the 1951 

 spawning migration in Cayuga Inlet was 15.2 

 inches. A female of this size produces approxi- 

 mately 43,000 eggs. 



It is obvious from figure 15 that great variation 

 in egg number occurred even among lampreys of 

 the same length. The major source of this varia- 

 tion was diversity in ovary size. Large females 

 tended to have a proportionately larger ovary and 

 fewer eggs per unit weight of ovary. 



Figube 15. — Regression of the number of eggs per female sea lamprey on total length. 



