DOWNSTREAM MOVEMENT OF SAIMONIDS 

 AT BONNEVILLE DAM 



Bonneville Dam is the first structure 

 across the Columbia River that adult salmon 

 and steelhead trout sunnount on their spawn- 

 ing migration, and the last one that down- 

 stream migrants pass on their way to the 

 ocean. The spillways and turbines of the 

 several dams completed, under construction, 

 or planned for the Columbia and its tribu- 

 t€a*ies present a series of hazards to the 

 young fish. Information on the time of day 

 when seaward migrants move downstiream may 

 be useful in the development of methods of 

 guiding them safely peist these structures. 

 If dame kill or injure significant numbers 

 of migrants, adjustments might be made at 

 critical hours to allow safe passage. For 

 example, if the turbines are less hamful 

 to downstream migrants than the spillway at 

 Bonneville, closing spillway gates for 

 short periods to coincide with peak down- 

 stream movement or when releeises from 

 hatcheries are moving past the dam would 

 allow more fish to peiss through the tur- 

 bines and thus minimize losses. This 

 report contains data collected at Bonne- 

 ville which may be useful as a guide for 

 protecting downstream migrants in this way. 



Earlier investigators detenained that 

 salmonids migrate seaward in much greater 

 numbers at night than during the day (Bar- 

 naby, l^kh; Hoar, 1951; Oregon State Game 

 Commission, Fishery Division, 1952). 

 Foerster (1929) noted that downstream- 

 migrant sockeye salmon ( Oncorhynchus nerka ) 

 migrated only at night at the start of the 

 run, all during the day at the peak of the 

 run, and only at dawn at the end of the 

 season. Data collected at Bonneville in the 

 present study indicated that, at least for 

 some species, maximum movement occurs at 

 dawn and dusk, and althou^ most downstream- 

 migrant salmonids move past the dam at 

 night, some migrate during the daytime. 



Members of U. S. Fish and Wildlife 

 Service collected all the data used in 

 this report. H. B. Holmes, K. G. Weber, 

 and C. J. Burner reviewed the maniiscrlpt 

 and made extremely helpful suggestions. 



METHODS 



The f ishways at Bonneville Dean have 

 auxiliary-water systems that transport 

 several hundred c.f .s. of forebay water to 

 the fishways and fishway collecting systems 

 through valve -controlled conduits. This 

 water provides additional flow to attract 

 upstream migrants into the fishways. Before 

 the auxiliary water enters the conduits, it 

 is screened to keep out debris and fish. 



Bypasses carrying 10 to 15 c.f.s. 

 were designed for sach screen pit when the 

 dam was constructed to provide a eafe down- 

 stream route for fish that entered the 

 auxiliary-water systems. Figure 1 shows the 

 location of the auxiliary -water systems and 

 fingerling bypasses. Inclined -plane fln- 

 gerling traps, designed by the Service, 

 were placed in all of the bypasses except 

 the one at the head of the Bradford Island 

 fishway. These traps capture all migrants 

 that pass through the fingerling bypasses 

 and counts of each species in the hourly 

 catches of these traps provide the data on 

 day and night movement past the dam of the 

 seaward -migrant fish. 



An advantage of the inclined -plane 

 trap is that it does not interfere with the 

 flow through the bypass and no migrants 

 elude the trap when it is raised to collect 

 the live fish. Figure 2 is a diagrammatic 

 drawing of an auxllisury-water screen pit 

 showing the positions of the conduits, 

 screens, bypfisses and inclined -plane fin- 

 gerling traps. 



No catch data from Teinner Creek by- 

 pass, which has not been sampled since 

 19^, are included in this report. 



The following species were studied: 

 Chinook ( Oncorhynchus tshawytscha ), blue- 

 back (O. nerka ), and silver (O. kisutch ) 

 salmon, and steelhead trout (Salmo galrd - 

 nerii) . In this report chinook finger- 

 lings are defined as chinook salmon that 

 migrate seaward during their first year of 

 life, wherecus chinook yearlings migrate 

 seaward during the spring of their second 

 year. Adult steelhead trout returning to 



