regained their equilibrium and were swimming 

 normally 10 feet below the ground line. There 

 are no indications that anelectrical field of 

 this type has any deleterious effects on the 

 downstream migration of fingerling salmon. 



APPLICATION OF THE ENTIAT TYPE 

 ELECTRICAL WEIR 



The "type B" electrical weir described 

 by Applegate, Smith, and Nielsen (1952), as 

 modified at Entiat, has a direct application to 

 salmon -cultural operations on the Pacific Coast. 

 The experimental installations have been con- 

 fined to comparatively small streams, less 

 than 200 feet in width and 8 feet in maximum 

 depth. It is doubtful if this weir could be ap- 

 plied to much larger streams without extensive 

 preliminary testing and probable alteration in 

 design. Most salmon operations, however, are 

 located on tributary streams which do not ex- 

 ceed these limitations. In general, most weir 

 sites are immediately suited or readily adapt- 

 able to the requirements of the electrical weir. 

 Although constricted flows at the weir site are 

 highly desirable unavoidable shallows do not 

 preclude the use of the electrical weir if pre- 

 cautions are taken to divert the fish from the 

 extremely shallow areas. 



The work of Andrew, Johnson, and Kersey 

 (1956) indicates that 60 -cycle alternating cur- 

 rent is to be preferred over direct current be- 

 cause it is more economical in operation and 

 no more injurious to salmon. The Entiat-type 

 electrical weir using 60-cycle, 110-volt, alter- 

 nating current as the energizing source has 

 further demonstrated the applicability of alter- 

 nating current for the diversion of adult salmon. 

 This type of electrical current is readily avail- 

 able from commercial sources . 



Observation indicates that salmon can 

 become conditioned to an electrical field and 

 that once they are conditioned, the weir will 

 lead them into a desired location. Placement of 

 the electrical field at a 30 -degree angle to the 

 perpendicular of the stream flow has proved 

 satisfactory for concentrating the fish in the en- 

 trance to the fish ladder. The upper end of the 

 fish ladder should be 5 feet below the ground 

 line, as shown in figure 2A so that the fish are 

 collected at the attraction point of the ladder in 



an area unaffected by the electrical field. The 

 leading qualities of the electrical field make it 

 highly desirable for the diversion of salmon. 



In any installation where electricity, at 

 reasonably high voltages, is used there is danger 

 to human beings. The electrical weir installa- 

 tion is no exception. The electrode cable is, of 

 course, electrified and any contact made between 

 the electrode cable and an adequate ground could 

 be dangerous to the person involved. How 

 serious would be the effect should a person fall 

 or be swept into the electrical field has not been 

 ascertained. It is doubtful if the effect would be 

 lethal but it certainly would be unpleasant. With 

 proper precautions, however, working on land 

 around the suspension system presents no prob- 

 lems. It is recommended that the area adjacent 

 to the weir be fenced and warning signs posted 

 to keep the general public away from the elec- 

 trified area . Figure 3 shows the precautions 

 taken at the Entiat weir site . 



The Entiat type weir with its free -swing- 

 ing, widely- spaced electrodes is particularly 

 adapted to streams which carry large amounts 

 of debris during the trapping period. It requires 

 no maintenance during such periods; this is in 

 sharp contrast to the labor involved in the opera- 

 tion of a conventional picket rack under similar 

 conditions. 



SUMMARY 



The "type B" electrical weir described 

 by Applegate, Smith, and Nielsen (1952) has 

 been adapted for the diversion of adult salmon 

 on their upstream migration. The electrical 

 field is created between a set of suspended elec- 

 trodes and a ground line by means of 110-volt, 

 60-cycle, single-phase, alternating current. 

 For the diversion of salmon, the length of the 

 field has been increased and the voltage gradient 

 reduced, as compared with lamprey -control 

 weirs, by using 3 -foot electrode spacings and 

 increasing the distance between the ground and 

 electrode lines to 15 feet. Minor alterations 

 were made also in the type of construction which 

 reduced installation and operating costs . 



The factors which influence the efficient 

 operation of the electrical weir are confined 

 principally to two sources, the water velocity and 



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