FURTHER EXPERIMENTS IN FISHWAY CAPACITY, 1957-' 



1/ 



by 



Carl H. Elling 



U. S. Fish and Wildlife Service 



Seattle, Washington 



ABSTRACT 



This is the second progress report on studies to determine the maximum number of fish 

 that a fishway may pass per unit time (capacity). The test fishway was a pool -and-overf all type, 

 4 feet wide, with a slope of 1 on 16 and a mean depth of 6. 3 feet. Maximum observed entry and 

 exit of salmonids are discussed as they relate to the determination of capacity. A sustained pas- 

 sage of 50 fish a minute was observed in a test in which the average weight per fish was 9 pounds. 



Behavior and performance of the fish were also examined. Results cited suggest that 

 certain experimental techniques may have influenced behavior of fish in the fishway . 



Experiments in 1956 to measure the 

 capacity of a pool-and-overf all- type fish- 

 way were continued during 1957. A report 

 of the initial work has been published 

 (Elling and Raymond, 1959). The recent 

 experiments sought further information on 

 fishway capacity, which is defined as the 

 "maximum number of fish (size and species 

 considered) that a fishway of given size 

 and hydraulic conditions may pass per unit 

 time." 



Basically, these experiments have 

 attempted to cinswer the question "How large 

 should a fishway be to accommodate a known 

 or anticipated number of migrating fish?" 

 Because of limited information regarding 

 space requirements for migrating salmonids 

 and the desire to provide a margin of safety 

 for the fish, fishways in some instances may 

 have been constructed of larger dimensions 

 than needed to accommodate the runs effec- 

 tively. Appreciable savings in construction 



\J Research financed by the U.S. Army Corps of Engineers 

 as a part of a broad program of fisheries-engineering 

 research for the purpose of providing design criteria for 

 more economical and more efficient fish-passage facili- 

 ties at Corps projects on the Columbia River. 



costs might be realized by reducing fishway 

 size, provided, of course, that these re- 

 ductions would not impair fish passage. 

 It is the purpose of these experiments to 

 determine how many fish can be passed per 

 unit time in smaller fishways than now in 

 use at large dams on the Columbia River and 

 what effect, if any, limited space may 

 have on fish behavior. 



After following initial attempts to 

 measure fishway capacity in 1956, it was 

 concluded that several changes in the phys- 

 ical structure of the test fishway would 

 be desirable before undertaking the 1957 

 tests. These revisions included a reduc- 

 tion in fishway width from 6 to 4 feet and 

 a change in weir crest design. Oh the 

 basis of 1956 experiments it was concluded 

 that considerably more fish thcin could be 

 readily accumulated would be required to 

 even approach capacity in a fishway 6 feet 

 wide. As there was no assurance of in- 

 creasing the supply of fish, the logical 

 recourse was to reduce fishway size. The 

 shape of the weir crest was altered to 

 eliminate unstable flow patterns which held 

 developed with use of a flat weir crest, 

 8 inches in width. 



