the fish. No additional fish were permitted 

 to enter the collection pool after tests 

 were under way. 



Fish were released from the collection 

 pool by raising a 5-foot gate in the grill 

 forming the upstream face of the collection 

 pool. The gate sill was approximately 2 

 feet below the water surface, allowing for 

 a water area 5 feet by 2 feet through which 

 the fish could pass to enter the introduc- 

 tory pool immediately downstream of the test 

 f ishway. This area exceeded the total entry 

 area into the fishway (4 feet by 1 foot) by 

 approximately 6 square feet, assuring ample 

 access to the fishway entrance. 



Two methods were employed to release 

 fish from the collection pool: a "brail 

 type" release and a "free" release. In the 

 brail release the collection-pool brail was 

 raised to within 4 feet of the surface just 

 before the release gate was opened. Once 

 the gate was opened and fish began to ascend 

 the fishway, the brail was tilted forward 

 gradually to encourage continued movement 

 out of the collection pool. This method 

 provided for a virtually complete utiliza- 

 tion of all fish in the collection pool 

 since the fish had no recourse but to move 

 into the fishway introductory pool and 

 thence into the fishway. However, the brail 

 method of clearing the collection pool 

 raised questions relative to the creation 

 of an unnatural stimulus during the release 

 period and its possible effect on the sub- 

 sequent behavior of the fish once they had 

 entered the fishway. Would fish which had 

 been somewhat artificially removed from the 

 collection pool perform in a normal manner? 

 Were we creating an artificial entry maxi- 

 mum as a result of the brail technique? To 

 obtain answers to these queries am alterna- 

 tive method, the free release, was employed. 

 This technique simply called for the entry 

 gate to be opened and for the fish to pass 

 from the collection pool and enter the 

 fishway on their own volition. At no time 

 was the brail used during the experimental 

 period. Two releases were conducted in this 

 manner . 



Another procedural change adopted in 

 some 1957 tests was to close the entry gate 

 when the observed maximum entry rate had 

 appreciably declined. In 1956 the gate had 

 remained open for the full 60-rainute test 

 period. The new procedure called for gate 

 closure generally within 30 minutes after 



the initial release (start of test). This 

 technique permitted more realistic deter- 

 mination of meain passage time through the 

 fishway since nearly all fish entering the 

 fishway introductory pool in the first 30 

 minutes could be expected to enter and pass 

 through the fishway by the end of the 60- 

 rainute test period. 



Recording Procedure 



Observers, stationed at each of the 

 seven weirs in the fishway, recorded up- 

 stream and downstream movement over the 

 weirs. These observations were transmitted 

 by push-button switch to an operations 

 recorder, the signals appearing instantcine- 

 ously as individual blips on a revolving 

 time tape. An additional observer was sta- 

 tioned at the final weir (60) to maintain 

 a tally by species. All tests were arbi- 

 trarily concluded 60 minutes after the entry 

 gate had been opened. 



Estimation of Passage Time 



Estimations of the average passage 

 time required to ascend the 6-pool fishway 

 were based on the observed entry and exit 

 per unit time in each trial. They Eire 

 considered estimates rather than absolute 

 determinations because any error in the 

 observed counts would naturally affect the 

 passage-time calculations. Two methods 

 were used to estimate passage time. One, 

 called "median elapsed time," based on me- 

 dian entry and median exit times was simply 

 the difference in the time at which half of 

 the fish had entered the fishway and the 

 time at which half of the total entered has 

 passed through the fishway. The "mean pas- 

 sage time" was derived in the usual manner 

 by taking the difference between the mean 

 entry and mean exit times for all fish 

 passed during the 60-minute test period. 

 Since the total number that negotiated the 

 fishway was rarely 100 percent, the estimate 

 of mean exit time was adjusted to account 

 for all fish remaining in the fishway at 

 the conclusion of the 1 -hour test. This was 

 done by arbitrarily assigning the 61st min- 

 ute as the time at which all remaining fish 

 completed their ascent of the fishway. The 

 resulting estimates of mean passage time are 

 biased (underestimated) by this procedure, 

 the extent of the bias depending on (1) the 

 percentage of fish remaining after 60 min- 

 utes and (2) the actual times that fish 

 would have remained before leaving. 



