McNARY DAM EXPERIMENT 



One set of 10 tests was completed at McNarj- 

 Dam (April 24 to May 26, 1961) to determine the 

 vertical distribution of juvenile salmonids. Each 

 te,st covered a single 8-hour fishing period, begin- 

 ning at 7 p.m. and ending at 5 a.m. Tests were 

 run only in intake C of unit 12, which is near the 

 center of the River channel. At the beginning of 

 each test, tlie turbine discharge was set at 354 

 c.m.s., producing a water velocity of about 1 m.p.s. 

 in the zone strained by the nets, as measured with- 

 out the nets in place (footnote 4). Te,sts were run 

 in pairs (2 consecutive days) with 6 nights be- 

 tween each pair. The gatewell was uncovered for 

 the duration of the experiment. 



The 0-group salmonids were scarce; only I- 

 group chinook and sockeye salmon and I-group 

 steelhead trout were taken in sufficient numbers 

 for analysis. Some ammocoetes were caught, but 

 tlie data are not included here. 



RELIABILITY OF CATCH DATA 



Three major factors could have affected the re- 

 liability of the catch data: (1) different fishing 

 efficiency of the fyke nets between day- and night- 

 fishing periods, (2) capture of fish as the nets 

 were drawn up through the water in the gatewells, 

 and (3) avoidance of the top net at The Dalles 

 Dam by fish that entered the gatewell before 

 reaching the net. 



Efficiency of the fyke nets could have varied if 

 fish were able to see the nets better during the 

 day than during the night. Recent experiments 

 in the Snake River below Brownlee Dam indicated 

 this possibility. Sims (unpublished)" found that 

 "scoop traps" were three times more efficient in 

 capturing marked fish at night than during the 

 day. Because vertical distribution of the fish was 

 constant, he sugge.sted that lessened visibility may 

 have been responsible for the higher trap efficien- 

 cies at night. Illumination within the turbine in- 

 takes was not measured during tests reported here, 

 but Secchi disc readings ranged from 0.43 to 0.85 

 m. at The Dalles Dam. In addition, the fyke nets 

 were located witliin the turbine intake (about 15 

 m. downstream from the mouth) under more than 

 20 m. of water (vertical distance through the 



" Sims. Carl W. Escapement of juvenile salmonld.s from Brown- 

 lee Reservoir. Fish-Passage Research Propram, Bureau of Commer- 

 cial Fisheries. .Seattle, Wash. Manuscript in preparation. 



water in the gatewell). The turbidity and the lo- 

 cation of the nets indicated that illumination wa,s 

 jjrobably not much higher during the day than 

 during tlie night. It seems unlikely that fish were 

 able to see the nets well during either day or night. 



Recognizing that fish might be caught as the 

 nets were drawn up through static water in the 

 gatewells, I examined the physical condition of the 

 fish to determine where, they were caught. Prior 

 experience had proven that fish would be dead 

 and extensively descaled when caught by nets in 

 water velocities equal to those in the turbine in- 

 takes. I reasoned that because water in the gate- 

 well was not flowing, fish from nets raised slowly 

 through the gatewell would be alive and suffer no 

 more harm than would bo caused by a dip net. 

 Few live fish were taken during the experiment; 

 when present, they were excluded from the catch 

 data. 



The catches made in the top net at The Dalles 

 Dam may not have been indicative of the actual 

 number of fish in that area because some may have 

 escaped by swimming into the gatewell through 

 the unscreened opening upstream from the net. 

 Modifications of the intake frame precluded avoid- 

 ance of the top net at McNary Dam. 



Available information concerning the three 

 points discussed in this section leads me to believe 

 that the catch data depict reliably the general be- 

 havior of fish in turbine intakes. Experimental 

 equipment and procedures that can circumvent 

 these potential sources of error are nevertheless 

 desirable for future experiments. 



DIEL MOVEMENT 



Data on diel movement of migrating juvenile 

 salmonids in turbine mtakes (intake B of units 1, 

 5, 10, and 11) at The Dalles Dam are presented in 

 table 1. Occurrence by age groups and species is 

 presented graphically in figure 6. 



The following conclusions seem to be warranted : 



1. Day and night passage for all age groups and 

 species did not differ significantly among intak&s 

 sampled (at both ends and the middle of the row 

 of operating turbines) . 



2. Although all age groups and species were 

 more abundant at night than during the day, only 

 the I-group salmonids were significantly more 

 plentiful. 



3. Of the I-group chinook salmon and I-group 

 steelhead trout, 94 and 85 percent, respectively, 



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U.S. FISH AND WILDLIFE SERVICE 



