Traveling Screens for Collection of Juvenile Salmon 

 (Models I and II) 



By 



DANIEL W. BATES and JOHN G. VANDERWALKER, Fishery Biologists 



Bureau of Commercial Fisheries Biological Laboratory 

 Seattle, Washington 98102 



ABSTRACT 



Two horizontal traveling screens were designed and operatedfor 2 years at the 

 Carson National Fish Hatchery, Carson, Wash. Deflection efficiencies were 100 per- 

 cent in 37 tests of over 11,000 juvenile coho, Oncorhynchus kisutch , and chinook 

 salmon, O. tshawytscha. The screens demonstrated their potential capacity to divert 

 young salmon moving downstream. 



ESTTRODUCTION 



This paper describes the fabrication, op- 

 eration, and efficiency of two horizontally 

 traveling screens (models I and II). The 

 screens are sinnilar to the deflection device 

 described by Brett and Alderdice (1958) in 

 which fish were guided to a collection area 

 with traveling cables. We used an endless 

 screen belt instead of cables. 



TRAVELING SCREEN 



In this section the general design of the 

 screens will be discussed, followed by the 

 major features of the design--the drive unit, 

 the tracking unit, and the screen belt and 

 supports --which will be described in detail. 



Drive Unit 



The drive unit (fig. 2) consisted of a 

 variable -speed d.c. motor and reduction gear, 

 pocket sheaves, and a drive chain. A 1-hp. 

 motor with a 10-170-r.p.m. reduction gear 

 was used in both systems. A pocket sheave 

 with a 56.5-cm, circumference, which ac- 

 commodated a 6.8-nnm. hand chain, was 

 mounted on the drive shaft of the reduction 

 gear. The maximum speed attained by the 

 chain was 1.5 m.p.s. (meters per second). 



The pocket sheave on the drive shaft, like 

 the other sheaves, had two notches cut in the 

 bottom rim to allow the hangers that supported 

 the screen to pass around it. Figure 3 shows 

 the track and chain with hangers (8-mm. 

 eyebolt welded to every 10th and 22d link in 

 the chain) for mounting the screen. 



Design 



The diagrammatic structure of the first 

 experimental traveling screen (model I) is 

 shown in figure 1. The fish are drifting 

 downstream tail first. The screen, which 

 resembles a conveyor belt on edge, was de- 

 signed to return upstream through the water, 

 but the extensive drag led to the development 

 of a second screen in which return travel 

 would be above and out of the water. This 

 second screen (model II), built several months 

 later, closely resembled model I except for 

 the return structure. The following sections 

 apply to both nnodels and describe the drive 

 units, tracking units, and endless screen belt 

 and supports. 



Tracking Unit 



A track guided and supported the chain as 

 it traveled between the sheaves (fig, 4), These 

 tracks were greased liberally to reduce fric- 

 tion. 



Screen Belt and Supports 



The endless screen belt was constructed of 

 spiral-wound carbon steel wire, like that 

 commonly used in fireplace screens. The 

 particular screen we used was 90-cm, wide, 

 with 8-mm, openings and a 72-percent effective 

 open area. 



The screen was supported by flat-bar steel 

 brackets, 3,2 mm. by 25,4 mm,, bolted to its 



