SEA LAMPREY OF CAYUGA LAKE 



589 



end of the month. On June 6 and 7 the percentage 

 of occupied nests had decreased to 12. 



In sections C through G where the spawning 

 population was high, superimposition of one nest 

 on another and the indefinite boundaries between 

 adjoining nests prevented accurate determination 

 of the total number of nests. In areas where 

 spawners were less numerous, nest building and 

 spawning were orderly. In such areas no super- 

 imposition or consolidation of nests was observed 

 and usually but one pair of lampreys was seen in 

 one nest. 



Table 30. — Occupancy of sea lamprey nests in Cayuga Inlet, 



between May SI and June 7, 1951 



(No observations on May 28 or June 2-5] 



Table 31. — Number and density of sea lamprey nests in 

 each 1-mile section of Cayuga Inlet, May SO- June 1, 

 1951 



[See fig. 10 for locations of sections] 



Date 



May 21 

 May 22 

 May 23 

 May 24 

 May 25 

 May 26 

 May 27 

 May 29 

 May 30. 

 May 31. 

 June 1. . 

 June 6.. 

 June 7.. 



The number of nests per section of stream as of 

 May 30-June 1 is considered a reliable index to the 

 total number (table 31 and fig. 12). This period 

 was chosen because it was the last date when 

 accurate nest counts could be made. The figures 

 given are believed to be only slightly lower than 

 the actual total numbers. 



The greatest density of nests, one per 15 feet of 

 stream, was found in section E, the area imme- 

 diately downstream from the U.S. Geological Sur- 

 vey dam. The first nest-building activities were 

 in this section. Section 6, the area just below 

 Newfield station, ranked second in nesting density 

 with one nest per 17 feet of stream. Sections D, 

 F, and C followed in decreasing order. Densities 

 were extremely low in sections H, I, J, and K, all 

 located upstream from the Newfield station. 

 These sections may be considered as of little im- 

 portance for lamprey spawning when low or mod- 

 erate water levels, similar to those of 1951, prevail 

 (see fig. 9 for water volumes). 



Some nests were not used for spawning, whereas 

 others were utilized by several pairs. An inves- 

 tigation into the number of nests actually utilized 



was made June 9 and 12, 1951, when 137 nests 

 were examined for eggs. A shallow rectangular 

 funnel, its mouth 18 inches square, made of brass 

 screen; 60 meshes per inch, was placed down- 

 stream from each nest. A few large stones were 

 placed alongside and slightly behind each nest to 

 guide the water current into the funnel. When 

 the funnel was in position the sand and gravel in 

 the nest pocket was scooped up with a shovel, 

 lifted to the water's surface, then slowly poured 

 back into the nest to free the lamprey eggs. This 

 process was repeated until some eggs were ob- 

 tained or until all material in and around the nest 

 had been thoroughly sifted. Lamprey eggs and 

 occasionally sucker eggs from the nest site drifted 

 downstream into the screen. The results revealed 

 59 (43 percent) nests with sea lamprey eggs, and 

 78 (57 percent) nests without. Five nests con- 

 tained an estimated 10,000 eggs or more. Only a 

 few hundred were recovered from most nests 

 which contained eggs. 



Spawning 



Gage (1893 and 1928) and Surface (1899) have 

 previously reported on the spawning of the Cayuga 

 Lake sea lamprey. A recent and more detailed 

 description was given by Applegate (1950) of 

 spawning in the Ocqueoc River, a tributary of 

 Lake Huron. Since Applegate's description agrees 

 well with observations made in Cayuga Inlet, com- 

 ments are limited here to an explanation of figure 

 14. (A) The female, on the left, is securely an- 

 chored by her oral disc to a stone at the upstream 

 edge of the nest; the male is brushing his oral disc 

 along the dorsolateral portion of the female from 

 the region of the first dorsal fin forward to the 

 head; (B) the male, above and to the right, has 

 just adhered to the top of the female's head and 

 has bent the posterior portion of his body to the 

 left in preparation to hold the female; (C) the 



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