576 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



better grasp of the magnitude of differences be- 

 tween Cayuga Lake and Seneca Lake stocks is 

 gained by further analysis of these three characters. 

 A divergence between the two populations in 

 number of cusps on the infraoral lamina was 

 found to be 56.2 percent. The divergence in 

 number of teeth in the lateral row was 62.5 per- 

 cent, and the divergence in the number of myo- 

 meres was 66.8 percent. Since the number of 

 laminae cusps, teeth, and myomeres are believed 

 to be genetic, and since the average divergence of 

 these characters differ at the racial level, it follows 

 that Cayuga Lake sea lampreys are to be con- 

 sidered a separate race from Seneca Lake sea 

 lampreys. 



Table 16. — Myomere counts on sea lampreys from Cayuga 

 Lake and Seneca Lake 



SPAWNING MIGRATION 



Tributaries of Cayuga Lake 



Each spring the sea lampreys pass from the 

 depths of Cayuga Lake into the tributary streams 

 to find suitable spawning sites. Practically all 

 the tributaries of the lake have natural barriers 

 near the mouth, a circumstance which substan- 

 tially limits the available spawning area. The 

 only tributaries that could possibly provide an 

 appreciable amount of nesting territory are : Saw- 

 yer Creek, Salmon Creek, Fall Creek, Cascadilla 

 Creek, Sixmile Creek, Cayuga Inlet, Taughannock 

 Creek, and Canoga Creek (fig. 24). 



Sea lampreys have never been reported from 

 Sawyer Creek, Salmon Creek, or Canoga Creek, 

 nor were they found in these creeks during this 

 study. A few adults were seen in all the remain- 

 ing streams mentioned except Sixmile Creek. 

 However, nesting or spawning lampreys were 

 found only in Taughannock Creek and Cayuga 



Inlet. Just four pairs of nesting lampreys are 

 known to have utilized Taughannock Creek, 

 whereas each year thousands of lampreys have 

 been observed spawning in Cayuga Inlet. Thus, 

 Cayuga Inlet is the only tributary of Cayuga 

 Lake that has significant value for lamprey 

 reproduction. 



Water Conditions in Cayuga Inlet 



The middle and lower portions of Cayuga Inlet 

 exhibit water conditions typical of a marginal 

 trout stream. At the U.S. Geological Survey dam, 

 5 miles upstream from the lake, the waterflow 

 varied between 63 and 18 cubic feet per second 

 during the period April 25 to May 23, 1951 (fig. 9). 

 The minimum and maximum morning (7 to 8 a.m.) 

 water temperatures during this period were 42° 

 and 64° F. Volume of flow was greatest early in 

 the season and decreased steadily throughout the 

 period, with the exception of a flood which oc- 

 curred on May 11. As the water volume de- 

 creased the water temperature gradually in- 

 creased, reaching its highest value (64° F.) on May 

 22, the time of lowest waterflow (18 c.f.s.). 



Migratory Behavior 



Sea lampreys are believed to assemble at the 

 mouth of Cayuga Inlet in early spring (February 

 and March). When water from Cayuga Inlet be- 

 comes warmer than the lake water, they begin 

 moving into the deep lower portion of the inlet. 

 They do not move into shallow waters until the 

 evening water temperatures reach nearly 50° F., 

 a value usually not attained until the latter part 

 of April. The year's first specimens were cap- 

 tured in Cayuga Inlet on May 4, 1950, 4 April 22, 

 1951, and April 19, 1952. 



Water temperature and lamprey activity are 

 closely correlated. After the lampreys arrive in 

 the shallow portions of the stream, a drop in water 

 temperature to the low forties drastically retards 

 activity. Upstream migration nearly ceases, and 

 even when handled the lampreys do not react with 

 as much vigor as they show when temperatures 

 are higher. 



Early migrants move upstream only during 

 darkness, hiding under rocks, logs, and debris dur- 

 ing the daylight hours. As the season progresses 

 their aversion to light gradually disappears and 



* Sea lampreys are believed to have arrived in Cayuga Inlet at least 1 week 

 prior to their capture in 1950. 



