area that sea lampreys -were observed on six nests built on a 

 gravel bed on the bottom of a deep bend of the river. The 

 depth to these nests was S'$ feet. In the Little Ocqueoc River 

 (station 5b) the average depth of 31 nests was 9.0 inches 

 (range: 6,0 to 1^.0 inches) (Appendix G, Table ?). For three 

 nests not included in this sample, depths of 5«0_, 5.5> and 6.0 

 inches were recorded (Figure 36). It is curious to note that 

 in the last cases, one inch or less of water was passing over 

 the rims of these nests. Spaivning had occurred at a similar 

 water level. 



Completed nests varied in size from 10.0 to 39.5 inches in 

 diameter. The average was about 19 inches and varied from one 

 sample area to another as follows: Stations IL-lii, 22.1 inches j 

 Stations IK-IL, 21.0 inches; Stations IG-UI, 19.3 inches; Stations 

 lE-lF, 18.1 inches. These stations are listed progressively 

 downstream and the decreasing average diameters are correlated 

 with diminishing amounts of suitable nest-biiilding materials 

 (Appendix G, Tables ^, 6). The average diameter of nests in the 

 shallow Little Ocqueoc River was 17.7 inches (Appendix G, Table 7). 

 These measurements yrere taken from rim to rim except for asymmetri- 

 cal ones for which a mean of greatest and least diameter was taken. 



Two generalized patterns of nest construction occurred indiere 

 adequate amounts of gravel were present. The most common of these 

 two was that built on the upstream faces of bars or ridges. These 

 nests were characterized by high downstream rims, very low or 

 non-existent upstream rims, and tended frequently to be asym- 

 metrical in outline shape and in structure (Figure 37b). This type 

 was foiind most often in midstream locations where the current 

 was moderate to swift and where the bottom had an irregular pro- 

 file. In such nests, the downstream rims were frequently elabor- 

 ated to a considerable height — occasionally as much as 10 inches 

 above the floor of the nest (Appendix G, Tables 5-7). 



The second general type of nest was characterized by a rim of 

 uniform height, a circular outline fonn, and a generally syranet- 

 rical appearance (Figure 37a). These nests were found at the 

 quieter margins of the stream, along the edge of, and at the head 

 and foot of pools, and in areas intermediate between bars and 

 riffles. Such areas had relatively slower current velocities 

 and the bottom had a flat or low profile. 



In all types of nests and under all circumstances, I have 

 seen sea lampreys moving stones to the upstream rims of their 

 nests although their success in maintaining this part of the 

 nest structure varied with the nest site and the velocity of the 

 current, as evidenced above. I see no basic functions of this 

 portion of the nest structure other than an additional repository 



- 106 - 



