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FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



anadromous, and until several decades ago was 

 considered to be primarily a marine species. In 

 recent years it has been demonstrated that lam- 

 preys can adapt themselves successfully to a lake- 

 stream habitat where conditions are suitable, as is 

 evidenced by their recent success in the upper 

 Great Lakes. Moreover, several lakes in New 

 York, including Cayuga Lake, have supported 

 landlocked populations of sea lampreys for cen- 

 turies 



During the Pleistocene period, when the glacial 

 Great Lakes were forming, glacial Cayuga Lake 

 was also passing through some profound altera- 

 tions. Changes in the outlet drainage of glacial 

 Cayuga Lake are of primary importance in this 

 discussion of the sea lamprey's establishment in 

 Cayuga Lake. 



Marine-dwelling sea lampreys may have pene- 

 trated into Cayuga Lake through any one of three 

 drainages. 



1 . The drainage of glacial Cayuga Lake south- 

 ward into the Susquehanna River. This outlet 

 opened up relatively early in the formative period 

 of the Great Lakes, but was later cut off by a lower 

 level drainage opened to the north and east 

 through the Syracuse, Mohawk, and St. Lawrence 

 outlets. 



2. At a later date, the Syracuse outlet (via the 

 Hudson River) may have permitted access to 

 glacial Cayuga Lake. 



3. A still later development was the final dis- 

 appearance of the ice in the St. Lawrence Valley 

 which permitted an arm of the 9ea to extend up 

 the St. Lawrence into Lake Champlain. This 

 situation would have permitted passage of the sea 

 lamprey from the Atlantic Ocean, via the "Cham- 

 plain Sea," into glacial Lake Iroquois and on into 

 Cayuga Lake. Another alternative passage in 

 existence during this same time was from the At- 

 lantic Ocean to the Hudson-Champlain estuary, to 

 the Mohawk outlet, into glacial Lake Iroquois, and 

 into Cayuga Lake. 



Because the first two routes mentioned above 

 would have permitted the sea lamprey to establish 

 itself in all the Great Lakes, which did not occur 

 until approximately the present century, it would 

 appear that the third route was the most probable 

 path of entrance. The fact that Niagara Falls 

 would have blocked their movement into Lake 

 Erie, and the other upper Great Lakes, lends 

 credence to the belief that the sea lamprey entered 



Cayuga Lake by way of the "Champlain Sea" or 

 the Hudson-Champlain estuary and Mohawk out- 

 let. Presumably, a sufficient supply of large host 

 fishes in the lake made possible the establishment 

 of a landlocked form of the sea lamprey. 



To date, size is the only morphological differ- 

 ence recorded between the marine form and the 

 landlocked form. The landlocked sea lamprey in 

 Cayuga Lake attains approximately one-half to 

 two-thirds the length of the marine form. 



SIZE, GROWTH, AND MORPHOMETRY OF 

 THE SEA LAMPREY 



Length Composition 



The sea lamprey of Cayuga Lake has often been 

 termed the dwarf form of the species. A miscon- 

 ception of its relatively small size was one of the 

 principal factors that prompted many authors to 

 consider it a separate subspecies. 



During the 3-year period 1950-52 the mean 

 total length of 3,363 sea lampreys captured in 

 Cayuga Inlet was 15.4 inches; extreme lengths 

 were 8.4 and 21.4 inches. Only unspent, up- 

 stream migrants are considered in this discussion. 

 A summary of length measurements, recorded in 

 table 1, is listed according to sex and year of cap- 

 ture. To facilitate a comparison of mean values 

 and their associated variation, these data are dia- 

 gramed in figure 1 . These diagrams are a modifi- 

 cation of the type originally employed by Hubbs 

 and Perlmutter (1942). The significance of dif- 

 ferences between samples can be judged by com- 



Table 1. — Summary of length measurements of sea lampreys 

 captured in Cayuga Inlet 



