DAUBLE ET AL.: SPATIAL DISTRIBUTION OF JUVENILE SALMONIDS 



459) (Fig. 7). Catches were low at barges 1 and 

 4, and no yearling chinook salmon smolts were 

 captured in the shoreline fyke nets. Overall 

 catches were significantly higher (P < 0.01) from 

 the bottom and middepths at barge 3 than for 

 any other station/depth combination. 



The number of spring chinook salmon smolts 

 collected per 100 hours of sampling averaged 

 from 0.3 fish at surface depth (barge 1) to 57.8 

 fish at bottom depth (barge 3) (Table 4). Al- 

 though station differences were not as pro- 

 nounced when CPUE was expressed by volume, 

 the greatest numbers of fish appeared to pass 

 barge 3 in the main river channel. 



Spring chinook salmon smolts ranged from 101 

 to 224 mm FL. Mean size varied little, possibly 

 because most of the fish originated from 

 hatcheries. Scale analysis confirmed that most of 

 the fish (171 of 173) were yearlings. 



Distribution of Sockeye Salmon Smolts 



Juvenile sockeye salmon were the third most 

 abundant salmonid gi-oup collected at the site. 

 These fish originated from wild stocks in upper 

 Columbia River tributaries, primarily the 

 Okanogan and Wenatchee River systems (Allen 

 1977). Peak catches of juvenile sockeye salmon 

 occurred in mid-May 1984. 



A total of 173 sockeye salmon smolts was col- 

 lected at the barge stations, but none were cap- 



Table 4. — Summary of average catch per unit effort for cfiin- 

 ook salmon smolts caugfit by fyke nets in spring 1984. No 

 smolts No smolts were caugtnt in the shoreline fyke nets. 



Station 



Depth 



Number/h x io^ Number m^ x 10^ 



tured by shoreline fyke nets. Most of the sockeye 

 salmon smolts (90%) were caught in midstream 

 areas (barges 2 and 3) from the middepth and 

 bottom sets (Fig. 8). Catch profiles indicated 

 that sockeye salmon smolts migi-ated at gi'eater 

 depths than other salmonids in 1984. Catches 

 from the bottom depth at barge 3 were signifi- 

 cantly gi-eater (P < 0.01) than catches from any 

 other station/depth combination. 



Catch per unit effort for juvenile sockeye 

 salmon averaged from 0.3 to 29.2 fish/100 h of 

 samphng, depending on station and depth (Table 



> 



12 



60 120 180 240 300 360 



Distance from Benton County Bank (m) 



Figure 8. — Cross-sectional distribution of sockeye salmon smolts (n = 173) 

 caught in shoreline and barge fyke nets during spring 1984. Note: horizontal 

 scale is reduced. 



783 



