of an obviously disoriented fish is shown in 

 figure 7. A track of one fish that resumed 

 migration upstream soon after release is shown 

 in figure 8. 



The initial aimless wandering of most of the 

 sonic-tagged fish may also have been character- 

 istic of untagged fish released in the reservoir ; 

 if so, they eventually recovered because a high 

 percentage of fish arrived on the spawning 

 grounds from releases in the reservoir. In 

 1962, for example, nearly 25 percent of the un- 

 tagged fish released in the reservoir were re- 

 covered in the spawning areas. In view of 

 the size of the Snake River (flow more than 

 365 c.m.s.)and the extent of spawning grounds 

 (over 25 river km.), we can be certain the per- 

 centage of fish that reached the spawning 

 grounds was far greater than the percentage 

 recovered. 



SNAKE RIVER 



More than half of the 44 fish with sonic tags 

 that were released in the Snake River covered 

 the 1.0 km. stretch to the weir in less than an 

 hour. Other fish moved more slowly. A few 

 fish remained in the release area up to 24 hours, 

 and one stayed 4 days before moving upstream. 

 Only one fish moved downstream; this salmon 

 drifted 2.4 km. below the release site, lingered 

 about 2 hours, and then resumed its migration 



BROWNLEE 

 DAM 

 1045 

 Oct. 25 

 RELEASED 



Figure S. — Chronolugifal record (diagrammatic) of a 77- 

 hour track of well-oriented adult chinodk salmon moving 

 SI km. upstream in Brownlee Reservoir. Fish carried a 

 sonic tag. 



upstream. Distributions that show the delay- 

 ing effect of the weir are given in figure 9. 



ELAPSED TIME - 



FOLLOWING 



RELEASE 



RELEASE POINT^ 



2 HOURS 

 (4RM.) 



5 HOURS 

 ( 6 PMI 



I9H0URS 

 ( a A.M.) 



Figure 7. — Disoriented movement of an adult <'hinook 

 salmon tagged with a sonic tag and released in Brownlee 

 Re.servoir. This fish, tracked for 106 liour-s, moved almost 

 continuously day and night and traveled about 81 km. 

 Travel was confined to area within 3.2 km. of the release 

 point. 



FiGLRE '.). — Diagram of the changing distribution of a group 

 of nine chinook salmon tagged with sonic tags and released 

 in the Snake River above Brownlee Reservoir. Two fish 

 presumalily passed through the weir between 4 and G p.m. 

 Xo fish were found farther than 2.4 km. downstream from 

 the weir. 



CHINOOK S.\LMOX P.\SS.\GE THROUCill BROWNLEE RESERVOIR 



43 



