DAUBLE ET AL.: SPATIAL DISTRIBUTION OF JUVENILE SALMONIDS 



Franklin County 



4 Sample Barge Location 



500 Feet 

 — I 

 150 Meters 



Benton County 



Figure 2. — Bathymetry of the Columbia River near the study site, and 

 relative position of barge sampling stations. Contour intervals are river level 

 elevations in feet. The stippled portion shows the midchannel region. 



result of this flow pattern. Velocities across 

 the river depended on location, station depth, 

 and river stage (Table 1). Maximum velocities 

 occurred near the river surface. Velocities at 

 midchannel ranged from 0.6 to 2.6 m/s and 

 velocities near the shoreline ranged from 0.1 to 

 0.5 m/s. 



Water temperatures ranged from 18.0°C in 

 August 1983 to 5.2°C in April 1984. Tempera- 

 tures were uniform across the river until late 

 May; however, from late May through Septem- 

 ber, daytime water temperatures differed by 2° 

 to 3°C between nearshore and midstream areas 

 because of solar radiation. Visibility (Secchi disc 

 depth) ranged from 142 to 440 cm. Visibihty was 

 at a minimum during the late spring freshet and 

 at a maximum in September. 



METHODS 



Several types of gear were used to provide 

 estimates of fish distribution. Offshore fyke nets 

 mounted on stationary barges were the principal 



Table 1 . — Mean river depth and current veloc- 

 ities at the fyi<e net sample positions during 

 spring 1984 studies. 



'Benton County stioreline 

 ^Grant County shoreline. 



777 



