ery of tagged and untagged fish released in the 

 reservoir. Graban (1964)* observed that tag- 

 ging mortality approached 30 percent. Al- 

 though total recoveries of tagged and untagged 

 fish in the 1960 experiments did not differ ap- 

 preciably — possibly because of the selection of 

 large, healthy fish for tagging — Hauck (see 

 footnote 1) reported, "A decrease in survival 

 (recovery) rates is indicated with increasing 

 water temperatures at release site. . . ." 



Recoveries of fish from the fin-clipped group 

 in 1962 also give evidence of stress from han- 

 dling: the percentage of returns was only 

 about one-third that of returns from untagged 

 salmon (table 2). The percentage of- recoveries 

 was higher from fin-clipped fish than from 

 tagged fish (even though handling procedures 

 were about the same for both lots), but most 

 of the fin-clipped fish were released when water 

 temperatures were declining and, hence, be- 

 coming more favorable for survival. 



SPAWNING SUCCESS 



Annual surveys by Richards '' and Pirtle and 

 Keating (1955) '^ provided percentages of to- 

 tally spent fish on the spawning grounds from 

 inspection of gonads and counts of eggs re- 

 tained before and after the filling of Brownlee 

 Reservoir in 1958 (fig. 5). These observations 

 showed that passage through the reservoir did 

 not affect the ability of fall-run chinook salmon 

 to spawn successfully. The difference between 

 percentages of totally spent fish in the preim- 

 poundment and postimpoundment years was not 

 significant. 



Information on the use of specific areas for 

 spawning by various salmonids was obtained 

 from surveys before and after the impound- 

 ment was formed and from discussions with 

 personnel of the Oregon State Game Commis- 

 sion, who annually surveyed spa^vning fish in 

 the Powder River and its major tributary — 



pi 



* Graban, James R. 1964. Evaluation of fish facilities, Brownlee and 

 Oxbow Dams. Snake River. Idaho Fish and Game Department, fiO pp. 

 [Processed.] 



* Richards. Monte. 1956-62. Snake River fall-chinook spawning 

 ground surveys. Idaho Fish and Game Department. Various pagination. 

 [Processed. ] 



' Pirtle, Ralph B., and James Keating. 1955. Annual report: The size 

 and timing of runs of anadromous species of fish in the Columbia and 

 Snake Rivers and their tributaries above the confluence of the Snake River, 

 1954. Idaho Fish Game Dept., Contract DA 3.5-02fi-eng-20G08. for U.S. 

 Army, Corps Engrs., 30 pp. [Processed.] 



60 191 



Figure 5.— Percentage of totally spent fall-run chinook 

 salmon recovered on spawning ground surveys in the Swan 

 Falls area, Snake River, 1954-62. Numerals in each bar 

 indicate number of fish. Brownlee Reservoir was filled in 

 1958. 



Eagle Creek ; the Idaho Fish and Game Depart- 

 ment carried out similar spawning surveys up- 

 stream from the impoundment in the Snake 

 and Weiser Rivers. Records of State fishery 

 agencies and of the Bureau of Commercial 

 Fisheries on the capture of juveniles migrating 

 from these various spawning areas also verified 

 previous spawning. 



The formation of Brownlee Reservoir appar- 

 ently did not affect the ability of anadromous 

 salmonids to use specific spawning areas. Fall- 

 run chinook salmon passed through the im- 

 poundment after construction of Brownlee 

 Dam and spawned in their accustomed area 

 near Swan Falls. Because no tagged fall-run 

 chinook salmon were observed in other spawn- 

 ing streams in 1960-62, straying evidently was 

 slight or nil. Spring-run chinook salmon and 

 steelhead trout, as evidenced by surveys on 

 spawning grounds and by catches of their 

 progeny in sampling traps, continued to use 

 widely separated spawning areas after the res- 

 ervoir was filled. Some spring-run populations 

 entered the Powder River about 32 km. above 

 Brownlee Reservoir and migrated into Eagle 

 Creek to spawn (fig. 1), whereas others passed 

 through the entire length of the impoundment 

 and continued into spawning grounds in the 

 Weiser River system. 



CHINOOK SALMON PASSAGE THROUGH TROWNLEE RESERVOIR 



41 



