20 



t 15 



o 1 



" Brail type " releose 



0© 



H 



" Free" releose 



H 



J 



500 1000 1500 



Total entering fishway 



2 000 



tests have demonstrated that surprisingly 

 large numbers of fish may pass through a 

 fishway of comparatively modest size. To 

 cite an example for comparison, the record 

 hourly count in a l-on-16-slope fishway at 

 Bonneville Dam is 4,296 salmonids (Bradford 

 Island Ladder, September 10,' 1946).!/ The 

 upper section of this ladder is 42 feet wide 

 and is joined by two lower branches, each 

 40 feet wide. In our recent tests, a fish- 

 way only 4 feet wide passed 50 salmonids 

 per minute (3,000 per hour), or roughly two- 

 thirds of the record hourly count in the 

 large Bradford Island ladder. 



SUMMARY AND CONCLUSIONS 



Figure 8. --Proportion of fallbacks as related to total fish 

 entering fishway in five 60-minute fishway 

 capacity trials, 1957. 



DISCUSSION 



It is perhaps well to emphasize some 

 of the factors to be considered in evaluat- 

 ing the results of these tests. Much of our 

 effort to demonstrate capacity in a fishway 

 was handicapped by an inability to secure 

 ample numbers of fish for test purposes. In 

 practice, there are perhaps only three or 

 four periods during the annual migrations 

 at Bonneville Dam during which fish are suf- 

 ficiently abundant to justify tests of this 

 design. Even then it has been necessary to 

 collect fish for a period of time to provide 

 ample numbers for testing. This technique 

 may have had some influence on the behavior 

 of fish cifter their release into the fishway. 

 Further, we are aware that performance in 

 fishways may vary with season and species. 

 This has complicated the process of compar- 

 ing tests conducted at different times of 

 the season, and therefore has necessarily 

 restricted the number of observations that 

 may be compared with confidence. 



The effect of fishway width upon the 

 passage of fish will require additional 

 study. In the 1957 experiment, a fishway 4 

 feet wide was used while a preliminary ex- 

 periment in 1956 utilized a fishway 6 feet 

 wide. Fluctuation in passage time due to 

 reduction in width cannot be adequately 

 assessed because of differences in hydrau- 

 lics and species composition of the respec- 

 tive experiments. 



Despite these limitations, the recent 



The 1957 experiments to measure fish- 

 way capacity (maximum number of fish pcissed 

 per unit time) were conducted in a 6-pool, 

 l-on-16-slope fishway only 4 feet wide. 

 Each pool was 16 feet long (weir center to 

 weir center) and averaged 6.3 feet deep. 

 There was a 1-foot rise between pools, and 

 heaid on the weirs was 0.8 foot. No orifices 

 were present in the fishway. Weir crests 

 were a Dalles-type design, and flows were 

 uniformly plunging throughout the fishway. 

 The total calculated flow was 11.8 c.f.s. 



All test facilities were housed in 

 the Fisheries-Engineering Research Labora- 

 tory, which is the principal component of 

 a specially constructed bypass on the Wash- 

 ington shore fishway at Bonneville Dam. 

 Fish were allowed to enter the laboratory 

 and collect in a large pool at the base of 

 the fishway structure. Collection periods 

 were limited to approximately 48 hours, 

 after which the fish were permitted to en- 

 ter the fishway. Lighting, approximating 

 outdoor conditions on a bright cloudy day, 

 was supplied by a batter of 1,000-watt 

 mercury-vapor lamps. 



The following observations were made 

 during the course of five 60-minute trials 

 in May and June : 



1 . The mcLxiraura observed entry for 

 Chinook salmon averaging 14 pounds was 61 

 fish per minute. In the same trial the 

 high average entry for a continuous 20- 

 minute period was 42 fish per minute. 



7/ Daily operation reports, U, S. Army Corps of Engineeis, 

 Bonneville Dam. 



12 



