590 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Figure 14. — A pair of spawning sea lampreys in Cayuga Inlet, May 1951. 



male, above, has completely encircled the female 

 by spiraling the posterior portion of his trunk 

 about her (note the thin opaque covering of the 

 male's eye; he is blind) ; (D) in the final stage, the 

 male, above and to the right, and the female 

 rapidly vibrate their bodies as both eggs and 

 sperm are emitted from their closely approximated 

 vents (fine particles of sand stirred from the floor 

 of the nest by the vibrating lampreys adhere to 

 the sticky surface of the eggs and aid considerably 

 in retaining them in the nest). 



Actual copulation lasts only a few seconds, but 

 is repeated at intervals of one minute to one-half 

 hour depending on water temperature, time within 

 the spawning season, and other factors. Spawn- 

 ing by a pair of sea lampreys commonly lasts about 

 1 % to 2 days. 



Fecundity 



Surface (1899) placed the production of eggs by 

 Cayuga Lake sea lampreys at an average of 

 27,500 (range of 25,000 to 30,000), and Gage 

 (1928) gave the fecundity of three specimens as 

 63,000, 65,000, and 108,270 eggs. Applegate 

 (1950) determined a mean of 61,500 eggs (cor- 

 responding mean length of 17.4 inches) and a 

 range of 24,021 to 107,138 in sea lampreys from 

 Lake Huron tributaries. Vladykov's (1951) esti- 

 mates of 72,870 eggs for sea lampreys from Lake 

 Michigan and 55,913 for Lake Huron specimens 

 agree well with Applegate's findings. 



The gravimetric method has been found to be 

 the most desirable means for calculating the num- 

 ber of eggs in a sea lamprey ovary. Detailed 

 studies by Applegate (1950) on the ovary of the 



