Dams in 1976 and 1977 (Gray and Haynes 1979). 

 Second, the 63*^ passage of internally radio- 

 tagged salmon in 113 h observed by Liscom and 

 Monan (see footnote 8) at Lower Granite Dam was 

 similar to the 699c passage of radio-tagged salmon 

 in 106 h that we observed in spring 1977 for fish 

 that crossed Little Goose Dam or were initially 

 released above it (Haynes 1978). 



Our studies provide the first information on 

 salmon movements near Little Goose Dam. Al- 

 though they affected salmon movements, spilling 

 and turbine operations are regular events at all 

 dams and would not appear to be solely responsi- 

 ble for excessive delays occurring at Little Goose 

 Dam. Fish passage delays may have resulted from 

 tagged salmon being forced to retravel a portion of 

 their migratory route after release. However, tag- 

 ging and transport stresses, per se, are common to 

 all tagging studies. Our salmon (1976-77) moved 

 to Little Goose Dam in an average of 38 h, a figure 

 consistent with similar studies at Bonneville Dam 

 (Monan and Liscom see footnotes 2-5). Thus, our 

 tagging and handling methods would not appear 

 to be responsible for extensive delays of salmon 

 movements upstream. 



Dropback and milling of radio-tagged salmon in 

 the Snake River at Little Goose Dam may be re- 

 lated to salmon trapping operations. Two factors 

 that may contribute to trapping effects are the 

 mechanical aspects of the trap itself and the 

 possible olfactory sensing of trapped salmon by 

 other salmon moving up the fish ladder. Trap en- 

 trances are narrow and steep, the trap emits sharp 

 noises when operating, and hydraulic fluid may 

 reach the fish ladder. It is well known that a 

 human hand in the water of a fish ladder can 

 interrupt salmon movement. Many authors 

 (Hasler et al. 1978) have demonstrated great ol- 

 factory sensitivity among salmon. The presence of 

 trapped salmon upstream and other disturbances 

 may inhibit salmon passage through fish ladders. 



Extensive passage delays, due to dropback and 

 milling and greater swimming depths in the spill 

 below the dam indicate a unique effect of Little 

 Goose Dam on the upstream migration of chinook 

 salmon. We observed delays at Little Goose Dam 

 averaging 148 ±64 h (Table 1). Delays reported at 

 other dams were significantly less (P<0.05) and 

 averaged only 66 ±31 h. Cause for great concern is 

 the 83 ±50 h average delay salmon encounter at 

 each dam while migrating through the Columbia 

 and Snake Rivers. Many salmon must pass eight 

 dams (Figure 1) to reach home spawning areas. 



and the additive effects of a 4 wk, multidam pas- 

 sage delay may significantly influence spawning 

 success, especially in fall run chinook salmon 

 which have shown the greatest decline in num- 

 bers. From 1962 to 1969, before Little Goose Dam 

 was operational, annual passage of fall chinook 

 salmon at Ice Harbor Dam averaged nearly 18,000 

 fish (U.S. Army Corps of Engineers*^). However, 

 in 1976 and 1977 fall chinook salmon passage at 

 Ice Harbor Dam was only 1,474 and 1,956 fish 

 (U.S. Army Corps of Engineersi^-i'*). Little Goose 

 Dam is 95 km upriver from Ice Harbor Dam (Fig- 

 ure 1). Since the position of fishways, navigation 

 locks, and spillways is different at each dam, ef- 

 fects of each dam must be studied independently. 

 Only then can methods be devised to increase pas- 

 sage success throughout the river system. 



Acknowledgments 



We thank C. D. Becker and the reviewers of the 

 Fishery Bulletin who criticized the manuscript 

 and made substantial contributions to its con- 

 tent; D. W. Crass, S. W. Cubberly, D. D. Dauble, 

 R. W. Hanf, Jr., J. C. Montgomery, and R. P. Ol- 

 son, who assisted data collection in the field; and 

 G. E. Monan, Northwest and Alaska Fisheries 

 Center, NOAA, Seattle, Wash., and E. Slatick, 

 Little Goose Dam, Starbuck, Wash., who kindly 

 provided information on National Marine 

 Fisheries Service telemetry studies and opera- 

 tional features of Little Goose Dam. The study was 

 supported by the U.S. Department of Energy 

 under Contract EY-76-C-06-1830 with Pacific 

 Northwest Laboratory, operated by Battelle 

 Memorial Institute. 



Literature Cited 



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189 



