The SFSR historically contained Idaho's largest salmon run, which is composed en- 

 tirely of summer chinook salmon. This race has been reduced from more than 5,000 

 returning adults in the mid-1950 's to about 700 returning adults in 1977. Almost all 

 of the SFSR chinook salmon spawn in the river and a few spawn in the tributaries. Some 

 juvenile chinook salmon hatched in the SFSR probably migrate into the tributaries to 

 rear. Fish populations in the study tributaries are dominated by rainbow trout, Salmo 

 gairdnevi Richardson, followed by chinook salmon, Dolly Varden, Salvelinus mdlma 

 (Walbaum) , brook trout, Salvelinus fontinalis (Mitchell), sculpin. Coitus spp. , cut- 

 throat trout, Salmo alarki Richardson, mountain whitefish, Prosopiton williamson-i 

 (Girard) , dace, Rhiniahthys spp., and sucker, Catostomus spp. 



The 23 tributaries, accounting for about 80 stream miles (130 stream km) were 

 described for fish population structure by using an average of one 50-foot (15.2 m) 

 study plot for every 465 yd (425 m) of stream. All streams were sampled randomly from 

 mouth to headwaters until the stream became dry. Each study plot was selected with a 

 table of random numbers, marked on aerial photographs (1-15,000), and then located on 

 the ground. The plots were located 100 feet (30.5 m) upstream from the photographic 

 location to avoid any bias resulting from the method of locating study plots. 



Stream Environment 



The aquatic survey used methods outlined by Herrington and Dunham (1967) , with 

 modifications (Platts 1974) to increase the validity in variable estimates and to quan- 

 tify additional physical conditions. The methods satisfactorily quantified most of the 

 variables, because water depths rarely exceeded 48 inches (122 cm) and water velocities 

 were never excessive for wading. The clear water with low flows (July-November) offered 

 excellent conditions for observational measurement. 



A transect (channel cross section) was used to identify the stream reach where the 

 aquatic structural analysis and fish population data would be taken. (A transect is an 

 imaginary line running perpendicular to the centerline of the stream.) Each station 

 included a cluster of five transects at 50-foot (15.2-m) intervals. The following 

 measurements and conditions were recorded: 



1. Stream, pool, and riffle widths. 



2. Stream depths at equal intervals across the stream. 



3. Ratings, locations, and features of pools. 



4. Streambed material. 



5. Cover, conditions, and types of streambanks. 



6. Channel elevations and gradients. 



7. Landtype association and landtypes. 



8. Stream order. 



9. Fish species and numbers. 



A given transect crossing the stream channel was divided into 1-foot (0.3-m) inter- 

 vals, and the dominant streambed material was classified as follows: 



Particle Diameter 



Classification 



12 inches or over (304.8 mm or over) 

 3 to 11.99 inches (76.1 to 304.7 mm) 

 0.185 to 2.99 inches (4.7 to 76.0 mm) 

 0.184 inch and less (less than 4.7 mm) 



Boulder 



Rubble 



Gravel 



Fine sediment 



2 



