In 19ii8 the shad run through the fishways was about twice as 

 large as that of 1938, and the night counts were made each hour. This 

 gives a "better idea of the movement of shad at ni[,ht as compared with 

 that during the daytime. Figure 10 shows the total counts for each hour 

 of the day at each ladder for the period July l-l5. The day counts (h a.m. 

 to 7 p.m.) follow the same pattern as indicated in figures 8 and 9 except 

 that during this particular period (the first half of July rather than the 

 last half) the peak counts were later in the afternoon than previously shown. 



The largest night counts were made during the hours iromediately 

 follovdng the day counts, but except for the counts at 8 p.m. they were very 

 s.iall in comparison with the day counts. It would appear from figure 10, 

 and from figures 8 and 9) that it would be more advantageous so far as shad 

 are concerned to shift the day counts 1 hour later — that is, start at 5 a.m. 

 and count until 9 p.m. 



Fish Locks 



The fish locks have not been used to any extent at Bonneville Dam, 

 and few shad were assisted by these devices except in I9UI. During that 

 year an extension of the powerhouse for the addition of four more turbines 

 interfered with the powerhouse branch of the Bradford ladder, and the power- 

 house fish locks were used that season to give full opportunity for passage 

 of fish. 



The fish locks are similar in principal to navigation locks. 

 Each lock consists of a vertical hydraulic chamber 20 feet by 30 feet in 

 floor plan which extends from the lowest tailwater level to the highest 

 headwater level. Near the bottom of the chamber is a gate-controlled 

 opening to the water below the dam. A similar opening near the upper end 

 of the chamber opens to the water above the dam. A conduit system entering 

 the bottom of the chamber provides for filling and draining. 



In operation, the entrance gate first is opened, and a moderate 

 quantity of water admitted throuji.h the bottom of the chamber flows out 

 through the entrance gate to attract fish into the chamber. The entrance 

 gate is then closed and the chamber is filled with water admitted through 

 the bottom. To assure that the fish will rise to the surface and leave 

 the chamber at the higher level, a movable grilled floor that remains at 

 the bottom of the lock chamber while the fish are entering is slowly raised 

 as the chamber fills '.irith water. This grilled floor, which slopes dovrnward 

 toward the exit side of the chamber, finally is raised to the water surface, 

 thereby gently urging the fish toward the exit. After this the exit gate 

 is closed, the lock chamber drained, the entrance gate opened, and the 

 ■•.'hole process repeated. The fish locks are constructed in pairs so that 

 one chamber can be open for the entry of fish while the other is making a 

 lockage. 



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