FISHERY BULLETIN; VOL. 87, NO. 4, 1989 



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Sample Interval (hours) 



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Figure 10. — Diel catch patterns of juvenile salmonids collected by barge 

 fyke nets during spring 1984. 



the juvenile salmonids estimated to pass the 

 study site in 1984. Wild populations of 0-age fall 

 Chinook salmon were more vulnerable to active 

 and passive netting techniques because they 

 were smaller relative to juvenile salmonids pro- 

 duced or released upriver. Because the smaller 

 0-age fall chinook salmon that emerge from 

 redds at Vernita Bar use the Hanford Reach 

 primarily for temporary feeding and rearing 

 (Becker 1973), their distribution may differ from 

 the distribution of smolts migrating from up- 

 stream sites. 

 The cross-sectional distribution of chinook 



salmon fry (36 to 70 mm FL) in our collections 

 was similar to that observed by Mains and Smith 

 (1964) for 0-age fall chinook salmon in the Co- 

 lumbia River at river km 550. Although Mains 

 and Smith also reported data from "yearling" 

 outmigTants in June and July, the length (85 to 

 90 mm FL) of these fish appro .\imated that of 

 later-migrating stocks of 0-age fish from up- 

 river. The spatial distribution described by 

 Mains and Smith for yearlings (based on volume 

 sampled) was nearly identical to the distribu- 

 tions that we obtained for naturally produced 

 stocks of 0-age fall chinook salmon. In both 



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