PASSAGE OF SALMONOIDS THROUGH A DARKENED FISHWAY -' 



1/ 



by 



Clifford W. Long 



U. S. Fish ahd Wildlife Service 



Seattle, Washington 



ABSTRACT 



An experiment to produce specific information on rate of ascent of salmonolds through a 

 darkened fishway was conducted in a short, pool -and -overfall fishway without submerged orifices. 

 The fish (98 percent steelhead - Salmo qairdneri) negotiated the 6-pool fishway significantly 

 faster in near-total darkness than in light conditions approximating a bright, cloudy day. 



JNTRODUCTION 



In the construction of fishways, occa- 

 sionally it is necessary to provide covering 

 to protect against slides and debris. Also, 

 it is not uncommon to find fishway channels 

 covered for roadway crossings, decking, and 

 other purposes. Such situations may result 

 in dimly lighted fishway channels, some of 

 which have been provided with artificial 

 lighting to simulate natural light prevail- 

 ing in outside fishways. 



Whether or not artificial lighting is 

 necessary or even desirable, has not been 

 fully demonstrated. Although experiments at 

 Bonneville Dam (U. S. Army, Corps of Engi- 

 neers, 1948) indicated that under suitable 

 hydraulic conditions salmonoids will pass 

 through a darkened fishway, specific infor- 

 mation on rate of ascent was not obtained. 



To provide answers to these questions, 

 an experiment designed to measure the effect 

 of total or near-total dcirkness on the pas- 

 sage of adult migrating salmonoids through 

 a pool- and-overf all fishway Wcis conducted. 

 Steelhead ( Salmo gairdneri ) comprised 98 

 percent of those fish tested. 



\/ Research financed by the U. S. Army 



Corps of Engineers cis a part of a broad 

 program of fisheries-engineering re- 

 search for the purpose of providing de- 

 sign criteria for more economical and 

 more efficient fish passage facilities 

 at Corps projects on the Columbia River. 



FISHWAY 



The experiment was conducted in the 

 Fisheries-Engineering Research Facility 

 which adjoins the Washington shore fishway 

 at Bonneville Dam on the Columbia River. 

 A by-pass diverts a part of the Washington 

 shore fishway flow through the facility and 

 back into the fishway again. Each day a 

 portion of adult salmonoids moving up the 

 Washington fishway were diverted into the 

 facility, and after passing through the 

 experimental area, they continued their 

 movement in the by-pass until they again 

 entered the main fishway. Figure 1 shows 

 schematically the elements of the facility 

 (described by Collins — ) essential to the 

 description of this experiment: neunely, 

 the collection pool in which the test fish 

 accumulated, the fishway introduction pool 

 into which the fish were released, the test 

 area (fishway), and the flow introduction 

 pool into which the fish passed after 

 ascending the fishway. 



The test area was a pool- and-overf all- 

 type fishway without submerged orifices. 

 The fishway was 4 feet wide by 96 feet long, 

 and consisted of six 16-foot pools with a 

 1-foot rise between pools. Because of the 

 sloped floor, water depth in each pool varied 

 from 6.8 feet in the lower end to 5.8 feet 



2/ Gerald B. Collins. Research in fish 



passage problems. U. S. Fish and Wild- 

 life Service. Manuscript in prepara- 

 tion. 



