In March 19^0 tne Washington Shore counting station was moved to 

 the upper end of the fish ladder, at forebay level. The upper six stop- 

 log weirs were replaced with weirs having submerged openings 8 inches 

 below the water surface as the only route of passage for water and fish. 

 This arrangement of weirs was considered superior as a means of regulating 

 the ladder at fluctuating forebay levels, but unfortunately proved to dis- 

 courage the passage of some species of fish, including shado In 19^0^ 

 only 57i| shad were counted through this fishway, as compared with 7j2li2 

 in the Bradford ladder « 



Hourly Counts at Bonneville Fishways 



Hourly counts of shad were studied in detail in order to under- 

 stand better the periods of maximum movements of shad in the ladder during 

 each 2l|.-hour period. From these data the optimum periods for shad migration 

 through the fish ladders were obtained. Thus,, the best time of day or night 

 in which to operate the ladders most effectively was determined. 



It is the normal practice at Bonneville Dam to count during two 

 8-hour shifts a day. The normal counting day begins at h a,m, and ends at 

 8 p,m. The counters on duty start counting on the hour and continue for 50 

 minutes. At the end of that time a gate is lowered in the opening through 

 which the fish swim while being counted^ The counter rests for 10 minutes 

 and promptly at the start of the next hour opens the gate and begins count- 

 ing again. The fish counted are credited to the hour the count begins. On 

 some occasions fish were counted at nighty but this is not the usual prac- 

 tice. When fish are not being counted the gates remain closed, so that all 

 fish ascending the ladders are enumerated. 



Since counts of shad were erratic and irregular at the beginning 

 and end of each run, the half-month period during which the run of each 

 year was largest for each ladder was taken to show the distribution of 

 counts throughout the day., The total number counted during this half« 

 month period of each year for each ladder is shown in table 3« 



It was observed that counts at the Bradford ladder were usually 

 low for the early hours^ reached a peak in the afternoon, and then dropped 

 off during the last 2 or 3 hours of counting. To illustrate this graphically, 

 the number of shad counted each counting hour for the largest half -month was 

 totaled (total for 6 a„m,j for 9 a.m., and so on) to eliminate minor daily 

 variations o These total hourly counts were calculated as a percentage of 

 the total of the half-month period so that each year's records were comparable 

 regardless of the sise of rim. These data for Bradford ladder are super- 

 imposed in figure 3 for all 13 years. It can be seen that in general the 

 number of shad passing through the ladder was low in the morning _, gradually 

 rose to a peak in the afternoon, and fell off during the last 2 or 3 hours 

 in the evening. The one exception was in 1939 (shown as a broken line) when 



15 



