Table 4. — Average size composition of bottom materials in the study streams ' 

 [All rocks larger than 105 mm. diameter have been excluded] 



Spawning area 



Harris River (intertidal) 



Harris River (upstream) 



Indian Creek (intertidal) 



Twelvemile Creek (intertidal). 

 Twelvemile Creek (upstream) _ 



Mean percent of total volume of solids retained by sieves with opening (in mm.) of— » 



26.26 13.33 6.88 



25.1 

 24.0 

 35.2 

 21.2 

 19.7 



14.6 

 16.2 

 15.3 

 15.1 

 13.9 



13.2 

 14.1 

 12.9 

 13.9 

 13.0 



11.0 

 11.8 

 11.3 

 12.5 

 12.9 



1.65 0.833 0.417 0.208 0.104 



7.9 

 8.4 

 7.3 

 8.8 

 9.6 



11.5 

 11.8 

 8.6 

 10.7 

 11.6 



10.5 

 9.2 

 4.9 

 8.4 

 9.5 



2.7 

 2.4 

 1.3 

 2.5 

 3.6 



0.4 

 .4 

 .4 

 .9 



1.2 



Percent of 

 total vol- 

 ume of 

 solids 

 settling 

 from 

 suspension 



3.1 

 1.9 



2.7 

 5.9 

 5.0 



1 For a description of methods of collecting and classifying samples, the reader is referred to McNeil and Ahnell (1964). 

 '■ Data are taken from table 2 of McNeil and Ahnell (1964). 



that the percentage of fine materials obtained from 

 the settling funnel used in the analysis of bottom 

 samples (McNeil and Ahnell, 1964) provides an 

 index of the relative amounts of extraneous 

 organic matter in spawning beds. Percentages 

 of fine materials passing through a 0.104-mm. 

 sieve, observed in the total volume of bottom 

 materials collected from the areas sampled, are 

 listed below in order of increasing values: 



Percent 



1 . Upstream Harris River 1.0 



2. Intertidal Indian Creek 2.7 



3. Intertidal Harris River 3.1 



4. Upstream Twelvemile Creek 5.0 



5. Intertidal Twelvemile Creek 5.9 



The rate of interchange between stream and 

 intragravel water is believed to be related to 

 gradient and roughness of the stream bottom. 

 Steep-gradient areas have a greater potential for 

 changes in curvature of the stream bottom than 

 shallow-gradient areas, and coarse materials give 

 greater roughness to the stream bottom than fine 

 materials. To index relative roughness, the study 

 areas are listed below in order of decreasing 

 amounts of solids retained by the largest sieve 

 used in this study (26.26-mm.). 



Percent 



1. Intertidal Indian Creek 35 



2. Intertidal Harris River 25 



3. Upstream Harris River 24 



4. Intertidal Twelvemile Creek 21 



5. Upstream Twelvemile Creek 20 



In addition to having the largest fraction of 

 coarse gravel, Indian Creek also had the steepest 

 gradient (0.7 percent as opposed to 0.2 to 0.4 

 percent for the other areas). The evidence 

 suggests that the interchange potential of Indian 

 Creek is greater than Harris River or Twelvemile 

 Creek. 



Spawning Density 



According to the evidence just presented, 

 environmental conditions related to oxygen supply 

 and survival of eggs and larvae would appear to be 

 most favorable in intertidal Indian Creek and least 

 favorable in upstream Twelvemile Creek. The 

 remaining three areas did not appear to vary 

 significantly with regard to the environmental 

 factors evaluated. Observed distributions of 

 spawning female pink and chum salmon appeared 

 to be related to the physical characteristics of the 

 spawning beds studied. 



For the years 1958, 1959, and 1960 intertidal 

 Indian Creek had the highest average density of 

 spawners, and upstream Harris River and Twelve- 

 mile Creek had the lowest. In order of decreasing 

 average density, the density of spawning females 

 in the sampling areas were estimated to be: 



1. Intertidal Indian Creek. 



2. Intertidal Harris River. 



3. Intertidal Twelvemile Creek 



4. Upstream Harris River. 



5. Upstream Twelvemile Creek 



mean = 35 females per 

 100 m. 2 (range 13 to 

 46 females per 100 

 m. 2 ) 



mean =29 females per 

 100 m. 2 (range 13 to 

 48 females per 1Q0 

 m. 2 ) 



mean= 17 females per 

 100 m. 2 (range 11 to 

 25 females per 1 00 

 m. 2 ) 



mean = 4 females per 

 100 m. 2 (range 2 to 

 females per 100 

 m. 2 ) 



mean =4 females per 

 100 m. 2 (range 1 to 

 10 females per 100 

 m. 2 ) 



508 



U.S. FISH AND WILDLIFE SERVICF. 



