FISHERY BULLETIN: VOL. 70, NO. 2 



PARTICLE 

 DIAMETER 

 IN CM 



ing density and low gradient contained 80% 

 particles under 1.3 cm in diameter (Figure 8C). 



WATER DEPTH AND VELOCITY 



Water depth and velocity were measured in 

 1960 in each of the eight study sections (Table 

 5). Three to five transects about equidistant 

 from each other were laid out across the stream 

 in each section. Velocity and depth were mea- 

 sured at about 0.3-m intervals along these tran- 

 sects with a Gurley impeller-type current meter' 

 mounted on a graduated rod and set at 12 cm 

 above the streambed, described as "fish depth" 

 for Pacific salmon." Volume of flow was com- 

 puted from the velocity and depth data collected. 

 The values presented are assumed to reflect con- 

 ditions normally encountered by fish selecting 

 spawning sites in the study sections, although 

 pronounced changes in water depth and velocity 

 may occur briefly during the spawning season 

 as a result of heavy rains. Sections with high 

 and low densities of spawners often had similar 

 water depths and velocities (Table 5: Depths — 

 Hidden Creek, section 9 versus 24; One Shot 

 Creek, section 4 versus 8. Velocities — Hidden 

 Creek sections 9 and 33 versus Up-a-tree Creek 

 section 15 and One Shot Creek section 8). 



Figure 8. — Particle composition by percent weight of 

 bottom materials in study sections having (A) high 

 spawning density and intermediate gradient, (B) low 

 spawning density and high gradient, and (C) low spawn- 

 ing density and low gradient. 



^ Reference to trade names in this publication does not 

 imply endorsement of commercial products by the Na- 

 tional Marine Fisheries Service. 



" J. S. Chambers, R. T. Pressey, J. R. Donaldson, and 

 W. R. McKinley. Washington State Department of Fish- 

 eries, Annual Report, 1954, submitted to U.S. Army 

 Corps of Engineers, 145 p. 



Table 5. — Average depth, velocity, and volume of flow in sections of high and low 

 spawning densities of Hidden, Up-a-tree, and One Shot Creeks, Brooks Lake, Alaska, 1960. 



454 



