The spaTOiing act of the sea lamprey has been more or less 

 elaborately described by Surface (1899), Hussal<of (1912), 

 Coventry (1922), and Gage (1928). The folloiTing description 

 agrees in general, but not always in detail, ■viath -fche statements 

 of these ivorkers. Briefly, my observations show that the act 

 is accomplished in the folloiving manner: The female orients her- 

 self in the bottom of the nest and anchors firmly with her oral 

 disc to a stone or larger piece of gravel lodged in the anterior 

 floor of the nest or to a similar object which has been placed 

 in the upstream margin of the nest during its construction. The 

 male approaches the female generally along the long axis of her 

 body "v^^iich is parallel to the current. In doing so, he fre- 

 quently runs his mouth lightly over the anterior half of her 

 body until the branchial zone is reached. At this point the 

 male fastens himself firmly to the female with his mouth. Almost 

 immediately he ^vraps the posterior third of his body in an abrupt 

 half -spiral about that of the female so that their vents are 

 approximated (Figures 30-31) • The extrusion of the eggs and milt 

 is preceded and accompanied by a very rapid vibration of the 

 bodies of both individuals for 2 to 5 seconds. Following that, 

 the male releases the female iramediatelj'. 



The fertilized eggs are carried by the c^Irrent into the face 

 of the doivnstream rim of the nest ivhere the majority of them 

 lodge in the interstices of the gravel rira that has been built 

 there. Very shortly after the spawning act, one or both of the 

 sexes anchor again to a rock near the head of the nest. With 

 violent body vibrations, they stir up a small cloud of sand 

 from the bottom of the nest which, like the eggs, is filtered by 

 the ciirrent into the spaces in the gravel and stone nest-rim and 

 which imbeds' the eggs in place. Reportedly, 20 to lj.0 eggs are 

 extruded during each act (Surface, 1899). I^ observations tend 

 to corifirm this, although I never found a satisfactory "vvay of 

 checking the accuracy with some mechanical device. Thereafter, 

 both male and female move about, adding more gravel or stone to 

 the doivnstream rim of the nest structure. This latter activity 

 may occur between each spawning act or between groups of two or 

 three successive spaivning acts. 



The interval between spaivnlng acts usually varies from one 

 to five minutes through most of the spawning activity. T/ilhen both 

 male and female are nearly spent, this interval may last ten min- 

 utes or longer. 



The duration of spawning by a pair (or other spawning combina- 

 tions) may be from 16 hours to three and one-half days. The 

 latter inten^al was displayed by one pair of very early spawners 

 in 19li7. During the peak of spawning activity in the river, all 

 combinations ivhose activities were followed closely completed their 

 spaiming in approximately 36 to ii8 hours. Late in the season, 

 during the month of July, tb.ree pairs observed at Station IB 



91 - 



