SEA LAMPREY OF CAYUGA LAKE 



587 



14 



TOTAL LENGTH IN INCHES 

 15 16 17 



XANTHINE ORANGE 



z RAW SIENNA 

 o 



BLUISH BLACK 



MALE 



-- FEMALE 



MAY 



APRIL 



350 375 400 425 



TOTAL LENGTH IN MILLIMETERS 



450 



Figure 13. — Regression of body coloration on total length of mature sea lampreys during April and May April 

 collections represent early migrants; May collections represent late migrants. 



observations made in Cayuga Inlet during the 

 present investigation. 



Sea lampreys that arrive in the spawning tribu- 

 tary in mid-April spend 4 to 5 weeks in the stream 

 before they begin nest construction. Those that do 

 not arrive until mid-May spend less than a day 

 in the spawning tributary before nesting. Prac- 

 tically all of the prespawning period is occupied in 

 moving upstream to suitable nesting sites. Late 

 arrivals utilize the low reaches of the stream, and 

 therefore spend little time in upstream travel 

 (p. 582). 

 Nest Building 



Water temperature seems to have a strong influ- 

 ence on the time of spawning. In Cayuga Inlet, 

 nest building usually starts toward the latter part 

 of May, when the evening water temperatures 

 approach 65° F. During the first few evenings of 

 nest building, the lampreys' movements are slow 

 and, if the water cools enough during the evening, 

 nest excavation may last for only a few hours. 

 These abortive attempts at nest construction 



indication of color transition that occurs during 

 the spawning period. All migrants acquired a 

 lighter color of from one-half to two color cate- 

 gories. The late migrants which were generally 

 darker made the greatest change. 



SPAWNING HABITS 



The spawning habits of the Cayuga Lake sea 

 lamprey have been reported by Gage (1893) and 

 Surface (1899). Coventry (1922) and Applegate 

 (1950) have reported on the spawning habits of sea 

 lamprey populations in the Great Lakes. In view 

 of the considerable available data on this subject, 

 only a brief summary will be presented here of 



