Table 3. — Distribution of passage times of individual ohinook salaon, sookeye salmon, and steelhead trout through 

 30.5 m. of 0.9-m. -diameter pipe at water velocities of 0.15, 0.3, and 0.6 m.p.s. April-July 1963 



95 percent confidence intervals about the median. 



from 56 to 100 percent for spring chinook and 

 from 81 to 96 percent for summer chinook 

 salmon. 



Median passage times required by sockeye 

 salmon to complete passage through the 0.3- 

 and 0.9-m. pipes were 9.4 and 3.0 minutes, 

 respectively. Although this difference between 

 the median passage times of the two pipes was 

 large, it was not statistically significant 

 (table 4). Percentages of sockeye salmon that 

 completed passage through the 0.3- and 

 0.9-rn. -diameter pipes were 73 and 93 percent, 

 respectively. 



Median passage times of steelhead trout 

 ranged from 3.3 minutes in the 0.9-nn. pipe 

 to 8.6 minutes in the 0.3-m. pipe. The 5.3- 

 minute difference between the median passage 

 times was not statistically significant (table 

 4). Percentages of steelhead trout that corn- 

 pleted passage through the two pipes were 96 

 and 80 percent, respectively. 



Entrance and Exit Conditions 



Two experiments were made to determine 

 the effects of changes in illumination at the 

 pipe entrance and exit, and in spacial transi- 

 tion from pool to pipe, on the entry and passage 

 of fish through a pipe. 



Changes in illumination. --The standard 

 lighting condition (1,000-watt mercury-vapor 

 lamps spaced 1.8 m, apart and 1.8 m, above 

 the water) required the fish to pass through 

 rather abrupt changes in illumination between 

 the nonilluminated pipe and the illuminated 

 introductory and exit pools (fig. 2), To deter- 

 mine if these sharp transitions impeded fish 

 passage, a series of tests was nnade in 1963 in 

 which passage was compared under sharp and 

 gradual changes in illumination--created by 

 placement of plywood covers on the intro- 

 ductory and exit pools. 



These tests were made in the 0.9-nn. pipe 

 at a water velocity of 0.6 m.p.s. on chinook 

 and sockeye salmon and steelhead trout. The 

 fish were not impeded by the sharp transi- 

 tion from the illuminated to the nonillumi- 

 nated pools. Median times required to com- 

 plete passage ranged from 2.6 to 4.1 minutes 

 when the light change was abrupt and from 

 2,8 to 3.7 minutes when the change was grad- 

 ual; all the fish completed passage (table 5). 



Changes in size . --During the 1963 experi- 

 ments and again when testing began in 1964, 

 observations of fish behavior in the introduc- 

 tory pool indicated a possible delay in passage 

 from the pool to the pipe. A connparison of 



