100 



CHINOOK SALMON 

 COHO SALMON 

 RAINBOW- STEELHEAD 



TROUT 



0.2 



0.5 

 VELOCITY (M.P.S.) 



0.8 



Figure 15. — Fish-collecting efficiency (mean percent) of 

 the electrode array and array trap during the control 

 conditions (power off) for each water velocity and 

 fish species. 



the array trap or (2) the fish-holding efficiency 

 of the array trap increased with increased water 

 velocity. In general, tlie rank of the species in rela- 

 tion to fisli-collecting efficiency of the electrode 

 array and array trap was the same as during the 

 power-on test; chinook salmon ranked first, coho 

 salmon second, and rainbow-steelhead trout third. 



Table 4. — Fish-collecting efficiency {in ^ percent) of the 

 electrode array and array trap during the control condi- 

 tions {power off) for each water velocity, test period, and 

 fish species 



ELECTRODE ARRAY ENERGIZED WITHOUT 

 ARRAY TRAP 



Fish-guiding efficiency of the electrode array 

 (power on), without the array trap, is presented 

 in table 5 as percentage differences between the 

 fish-guiding and collecting efficiency of the elec- 

 trode array and array trap with the power on and 

 the efficiency with the power off. Table 5, however, 

 is only an indication of the actual fish-guiding 

 efficiency of the electrical guiding system. As pre- 

 viously mentioned, fish swimming more than 0.9 

 to 1.2 m. from the electrodes were not visibly 

 affected by the electrical field created by the elec- 

 trode array. As the entrance to the array trap was 

 G.4 m. wide, it was possible for fish migrating near 

 the middle of the experimental canal (i.e., near the 

 middle of the trap entrance) to enter the array 

 trap without having been diverted by the electrical 

 energy. These fish, therefore, were not actually 

 available to be guided by the electrical system. 

 Assuming that the same percentage of fish entered 

 the array trap naturally (i.e., without being- 

 guided) during the power-on conditions as during 

 the control periods, we established the following 

 relations to determme the actual fish-guiding effi- 

 ciency of the electrical system alone : 



Let ATp= Total number of fish captured in the 

 array trap on any given power-on day. 



ISTp=Total number of fish captured in the 

 inclined-screen trap on the same 

 power-on day. 



ATo=Total number of fish captured in the 

 array trap on the preceding power-off 

 day. 



ISTo=Total number of fish captured in the 

 inclined-screen trap on the same 

 power-off day. 

 Pe= Percentage of fish guided by the elec- 

 trical system that were actually avail- 

 able to be guided; i.e., fish that would 

 not have entered the array trap 

 naturally. 



Then P. 



ATp 

 "ATp-flSTp 



(AT„) 



-[ 



(ATo+ISTo) 



(ATp-MSTp) 



-[ 



(ATo) 



(ATo-flSTo) 



(ATp-flSTp) 



-^xioo 



FISH-GUIDING EFFICIENCY OF AN ELECTRICAL GUIDING SYSTEM 



321 



