for materials removBd from the center of the nest area and as 

 a provision for anchorages to ■which the female may attach her- 

 self during the spaiiming act. A single large piece of gravel, 

 a sma3.1 imbedded stone or stick, or even a hardpan claj'- bottom 

 has been observed to suffice for the latter requirement. 



Nest-building on sites less favorable tiian the foregoing 

 variously alters the form of the structure. Occasional nests 

 ■were built by clearing an area betiveen tivo or more large stones 

 which formed ■vra.lls on each side of the nest. The erratic ■water 

 •turb-'olence on such sites caused the nest to suffer from some 

 scouring vihen the sparmers vrere no longer present to maintain 

 it. An examination of these nests proved that an ejccessive 

 mortality of eggs and developing larvae resulted. 



■Where nests iTere built from a thin layer of gravel and sand 

 over hardpan clay, the upstream margin of the nest -was soon 

 sTrept away by the current as were the contents of the floor, 

 leaving only a modified crescentic ring of gravel for the nest 

 (Figure 37c). With no anchorage upstream or down, this structure 

 vfas slowly demolished by the current and again I found from a 

 dissection of such nests before hatching had occurred that a 

 heavy mortality of eggs or larvae resulted. 



In ■the preceding instance, and in those sandy areas where 

 small, scattered patches of gravel provided nesting sites, the 

 apparent minimal conditions acceptable for sea lamprey nest 

 construction are represented. In the latter case, where pockets 

 of gravel lay ahead of, or against, small hummocks of sand or 

 sand bars, the gravel was placed by the lainpreys against the 

 ■cLpstream face of such rises (Figure 37d). The amount of gravel 

 utilised varied, of course, "I'vith the available supply. One such 

 nest consisted of a double layer of 3/h- to 1-inch gravel, 

 appro:clmately one square foot in area, v;tiich had been built 

 against a small, sand hummock. All available gravel in the area 

 had been utilized (Figure 37e)o A pair had previously been ob- 

 served spa^wning in this poor nest. Examination of the nest after 

 the completion of this act disclosed very fev/ fertilized eggs. 

 The potentially hig^ mortality of eggs on such sites as these 

 has also been noted elseivhere. Nest construction and spawning 

 were never observed on sites providing a lesser volume of hard, 

 bottom- type elements than in that situation noted just previously. 



A miscellany of nests were located oddly under snags, v/ater- 

 logged timber, and partly submerged briish. Immediately below 

 Ocqueoc Lake (Station IB), riffle areas were created by ejcten- 

 si-v8 beds of clam shells. These, ■with some gravel were the basic 

 material utilized by lampreys for nest construction. The relative 

 success of spavming on such sites was not detennined. 



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