deficiency, a third row of electrodes was 

 added to create a zone of lov;er voltage 

 gradients on the upstream side of the array 

 to divert the large fish before they were 

 subjected to the high voltage required to 

 divert small fish. When placed in the 

 field, however, the result was a rather 

 formidable mass of electrodes that immedi- 

 ately raised questions of practicability 

 for large-scale installations. 



Observations of fish behavior during 

 field experiments at Jenkins Creek in 

 1954 —^ indicated that a number of fish had 

 been successfully diverted without having 

 entered the field between the rows of elec- 

 trodes. Attention in the laboratory was 

 therefore shifted to a different type of 

 electrical field requiring only a single 

 row of electrodes. In laboratory tests the 

 single-row array proved to be as effective 

 as those with two and three rows. However, 

 the directional relationship of the field 



to the water flow was so different from that 

 in the earlier arrays that the question was 

 raised whether the response was still due 

 to electrotaxis. If the reaction to the 

 field were simply one of avoidsmce of a dis- 

 agreeable stimulus rather than a reflex 

 reaction to the directional properties of 

 the field, it would allow much greater flex- 

 ibility in electrode pattern cind electrical 

 circuitry. If, on the other hsind, electro- 

 taxis were involved, knowledge was required 

 of the most desirable relation of field 

 polarity to the direction of water flow. 



The major objectives of the tests 

 described here were to determine whether 

 reactions of the fish are caused by avoid- 

 ance or by electrotaxis, and if the latter, 

 to determine whether an upstream or down- 

 stream field polarity orientation is more 

 effective. 



MATERIALS AND METHODS 



2/ Hunter, Charles J. Manuscript in 



preparation. "Experimental guiding of 

 salmonids by electricity, Jenkins Creek, 

 1955," 



DISCHARGES 



Figure 1. --Plan of experimental tank. 



The experiments were conducted in the 

 spring of 1955 in the tank (fig. 1) used by 

 Raymond (1956). In the experimental area 

 (14 by 17 feet) the depth of the running 

 water was 12 to 13 inches, A screened 



baffle designed to produce 

 uniform water flow served to 

 keep fish from moving upstrecim 

 out of the experimental area; 

 screens also blocked the lower 

 ends of the trap area. The 

 traps were fitted with swing- 

 down gates which the operator 

 could release simultaneously. 

 Electric pumps of 1,000 gal- 

 lons per minute combined 

 capacity created a water flow 

 of approximately one-half foot 

 per second. 



Although water tempera- 

 tures ranged from 57" to bS'' 

 F, during the 12 days of the 

 experiment, the daily fluctua- 

 tion in temperature was less 

 than 2° F. 



The test fish were year- 

 ling silver salmon ( Oncorhyn - 

 chus kisutch) obtained from 

 the Washington State Depart- 

 ment of Fisheries hatchery at 

 Issaquah, Washington. They 

 ranged from 8.4 cm. to 12.9 



