Items one to three alone are considered adequate evidence of 

 establishnent of the species in these lalces. Data collected else- 

 ivhere seem to indicate that transforming and neTrly-transfonned 

 sea lampreys generally do not become established in smaller and/or 

 less suitable lakes in a -watershed, but pass directly dovmstrearn 

 to the Great Lalces. 



Other inland lakes, connected more or less directly -with the 

 Great Lalces, are undoubtedly acting as additional reservoirs for 

 adult populations. We have received several reports of adults 

 being taJcen during the ivinter months in Lalce Charlevoix (Charlevoix 

 Cotinty) on speared v.^itefish, perch, and ciscoes. Dr. A. H. Stockard 

 of the Zoolos^ Department, University of Michigan, reported on 

 November 6, 19U7j that fisherraen in Lake Charlevoix were spearing 

 sea lampreys that had attached themselves to the bottoms of their 

 power boats. Fishermen trolling in the same lalce report sea lampreys 

 attaching themselves to the stern of the moving boat. 



We have also received several reports indicating the presence 

 of sexually immature adults in Pentvrater Lake, Oceana County. 

 Like Lalce Charlevoix, this lalce is connected directly vd-th Lake 

 Michigan by a short channel. The most reli-able ox these reports 

 concerned an 13.5-inch sea lamprey attached to a 5-pound rainbow 

 trout that was talcen on November 1, 19U7. Reports of sexually 

 immature adults in Big Platte Lake, Benzie County, and White Lake, 

 Iviuskegon County are likewise considered reliable. 



Lake Fenton, Genesee County; Little Traverse Lake, Leelanau 

 County; Lake Genesarath, Beaver Island; Round Lake, Kalkaska 

 County; Pipestone Lake, Berrien County; and Big Paw Paw Lalce, 

 Berrien County; allegedly contained sea lampreys in 19U7 or 19U8 

 but I consider these reports doubtful. 



Effect of obstructions and barriers to migration 



For the purposes of this discussion, a barrier to migration is 

 differentiated from an obstruction to migration in that the former 

 cannot be surmounted by migrating sea lampreys whereas the latter 

 can be passed with varying degrees of difficulty, which may have 

 some selective action among the migrants. The sea lamprey can and 

 does negotiate many kinds of falls and low or irregularly constructed 

 dams of moderate height. A good example of this is in the Ocqueoc 

 River, Presque Isle County, where nearly one-half of the spavming 

 migrants work their way over two natural falls, h»S and 6 feet high, 

 and an old cement mill dam (Figures U and $) . In another instance, 

 migrants are known to pass over (or through?) an irregularly con- 

 structed logging dam of some heif^t situated in Silver Creek, Iosco 

 County. 



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