In I9UI the powerhouse fish lock was operated throughout the 

 time of the shad runo The half-month period of highest counts that year 

 was the same for all three fish-passing facilities. The counts for each 

 fishway during this period of highest counts are shown in figure 11. The 

 trends of counts for the Bradford ladder and the fish locks arfe similar 

 except that the peak counts in the locks occurred 2 or 3 hours earlier than 

 in the Bradford ladder. If the locks and ladder were assisting the same 

 group of fishj as they might well have been^ the difference of -a couple of 

 hours of peak count might be the time it takes the shad to ascend to the 

 counting station on the ladder. Those in the locks are lifted immediately 

 from the lower water level to the higher, elii-ninating the time necessary to 

 svdm to the higher level. On the Washington Shore, the peak counts were 

 earlier than in either of the other two facilitiesj as has already been 

 shown in figure 9, this seems to be a characteristic of the Washington 

 Shore ladder. 



For the whole season, U, 939 shad were assisted over the dam by 

 the fish locks as compared with 5,806 by the Bradford Island ladder and 

 7,862 by the Washington Shore ladder. It can be seen from this and from 

 figure 11 that the powerhouse fish locks apparently were almost as effec- 

 tive as the ladders in assisting shad over the dam^ 



Mortalities in Fish Ladders 



During some years the shad experienced considerable difficulty 

 in ascending the ladders. This occurred, or at least was especially 

 noticed, above the counting stations. A statement to this effect is 

 found in the I9U8 report of fish passage over Bonneville Dam, U. S. Arinj'', 

 Corps of Engineers, I9U8, which reads: 



When the forebay is raised, due to high flood water, 

 to elevation + 82 feet it is necessary to raise the weirs 

 above the weir 70 counting station a total of ten feet, 

 so as to create a gradual rise to the 82 level. When 

 these weirs are raised by addition of stop logs, inimical 

 hydraulic conditions are created for shad migration 

 above the weir 70 counting station. Many shad dislike 

 to, or cannot ascend through this area and consequently 

 become weakened and are then forced at;ainst the picketed 

 fish leads where the water velocity imprisons them until 

 they die. Mortalities as high as 1$% and 2Q% have been 

 sustained in past years^ however, in I9U8 the losses were 

 minor ....... 



In I9U9 the shad run began after the water had lowered somevjhat 

 below the maximum of 82.5 feet, and this species apparently negotiated 

 the fish ladders vjith ease as stated in the 19ii9 report (19h9, U, S. 

 Army, Corps of Engineers) 5 " . . . with less rigorous hydraulic 

 conditions in existence above the weir 69 counting station, the shad 

 were able to ascend with cast to the forebay." 



23 



