Under such conditions, preferred nest-bxiilding sites covild 

 only be determined by ascertaining in limited areas the serial 

 order in Tshich they were occupied. A gravel riffle area, 80 feet 

 long^ iriiich lay between deep pools at tiro bends of the river 

 (stations Ur-IM), a predominantly sandy-bottomed area at Station 

 2C, a gravel bed in a bend of the river at Station IE, and gravBl 

 riffles in a small stream (Station 5B) were observed during the 

 spa.vming season. It was found that, in general, the upstream 

 face of the gravel bars forming the longer riffle areas and that 

 of transverse gravel bars of all descriptions were utilized first 

 for nest construction. Following this, the depressions between, 

 and occasionally the crests of, these bars were used. In such 

 areas, the last sites taken were those within the foot of the 

 pool proper, upstream from the riffle, and those at the head of 

 the pool lying just downstream from the riffle (Figure 3h). "When 

 all such sites had been preempted, nests appeared on flat, gra- 

 veled areas along the outside margins of pools, and oh linear 

 bars, patches, and pockets of gravel in the sandy areas of the 

 river. 



In the lotrer reaches of Zone 1, above Ocqueoc Lake, graveled 

 areas frequently appeared on the outer portion of bends in the 

 rivero These graveled areas were generally composed of a series 

 of crescentic gravel bars, dipping from the shoreline to the 

 deepest water in midstream. Within the limits of such an area, 

 nests were built first on the upstream face of the bars at depths 

 of 12 to 2U inches. Thereafter, similar sites were occupied in 

 shallower water ri^t to the water's edge and to depths of three 

 and one-half feet near the midstream limits of the bars. Areas 

 intermediate between, or upstream or downstream from, the gravel 

 ridges were settled on last (Figure 3$). 



In a small stream, the Little Ocqueoc River, a continuous 

 series of closely spaced gravel riffles was present, although 

 the profile of these bars Wcls quite low. Here the sea lampreys 

 selected nest-building sites initially on the upstream face of 

 the gr'avel bars and laterally in the intermediate areas without 

 much discri.mi nation (Figure 36). 



In Zone 1, sea lamprey nests were b\iilt at depths ranging 

 from 5 inches to 5.? feet. Most spawning occurred, however, in 

 depths between 12 and 2$ inches (depths to center of floor of 

 nest). 



In the generally graveled area between Stations IL and IM, 

 the average depth of 1^6 nests was 22.1 inches (range: 8.^ to 2lt,0 

 inches) (Appendix G, Table 5)j between Stations IK and IL, the 

 average depth of 3k nests was 20.2 inches (range: 11.0 to 32,0 

 inches) (Appendix G, Table 6)j and in the generally deeper waters 

 between Stations IE and IF, the average depth of 7U nests was 

 22,1; inches (range; 7.5 to 38.0 inches). It was in this last 



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