Figure 3. — Boat following chinook salmon with sonic tag 

 in Brownlee Reservoir. Electronic tracking equipment 

 pro\aded precise data on day and night movements of 

 tagged fish. 



information on movements of individual fish in 

 the reservoir by tracking them in a boat 

 equipped with receiving equipment and plotting 

 their positions on a chart at about 5-minute 

 intervals (fig. 3). In the Snake River, the date 

 and time of passage of fish with sonic tags past 

 specific points was automatically recorded on 

 time-event charts connected to fixed monitors - 

 placed along the shoreline (fig. 4) . Information 

 on movement of individuals and groups of 

 tagged fish between monitoring stations was 

 obtained with portable hydrophones on a skiff 

 propelled by an outboard motor. 



RECOVERY 



Marked and unmarked chinook salmon were 

 recovered from the spawning area in periodic 

 surveys from October to mid-January. The 

 surveys were made monthly for the 1960 

 spawning run by the Idaho Fish and Game De- 

 partment and weekly for the 1961 and 1962 

 runs, when the Bureau of Commercial Fisheries 

 assisted the Department. 



During the surveys, observers drifted dovsm- 

 stream in a small boat or waded through shallow 

 areas to search the entire known spawning 

 area for carcasses. The dead salmon were ex- 



2 Johnson. James H. 1963. Development and use of sonic tracking as an 

 aid to Pacific salmon conservation studies, 13 pp. [Processed.] 



Figure 4. — Locations along Snake River between Brownlee 

 Reservoir and the mouth of Pa.yette River where fixed 

 monitors recorded the passage of upstream-migrating 

 chinook salmon carrying sonic tags. 



amined for tags, fin clips, and spawning stages 

 and then marked with spaghetti-type tags to 

 identify them on future surveys. SCUBA div- 

 ing was added in 1962 for investigation of deep 

 pools where the spent fish might accumulate 

 and remain unobserved. The greater recovery 

 effort in 1962 — plus experience gained in 

 searching for fish in 1960-61 — may have led to 

 higher rates of recovery of untagged fish in 

 1962 (24.9 percent) than in 1960 (5.1 percent) 

 or 1961 (14.3 percent). Water level and clarity 

 appeared to be about the same for the 3 years. 



PROPORTIONS OF FISH 

 REACHING SPAWNING GROWNDS 



In evaluating recoveries from both release 

 sites, we considered the possible effect of differ- 

 ences in hauling time and post-release environ- 

 ment on the eventual passage of chinook salmon 

 to the spawning grounds. Differences in haul- 



CHINOOK SALMON PASSAGE THROUGH BROWNLEE RESERVOIR 



39 



