EBEL: TRANSPORTATION OF CHINOOK SALMON AND STEELHEAD SMOLTS 



Dam for 1971, 1972, and 1973 were 0.8, 0.4, and 

 0.2%, respectively. These estimates did not in- 

 clude fish that were transported. A substantial 

 increase in survival of transported steelhead is 

 indicated by both analysis of test/control ratios 

 and comparisons of percentage returns of adults 

 from transported groups with percentage returns 

 of adults to Dworshak Hatchery and Little Goose 

 Dam. 



Percentage returns from production releases of 

 juvenile chinook salmon to Rapid River Hatchery 

 (Parrish^^) in 1971, 1972, and 1973 were 0.59, 

 0.12, and 0.15%, respectively. The corresponding 

 percentage returns from juvenile chinook salmon 

 transported from Little Goose Dam were 0.77, 

 0.11, and 0.52%, respectively. Estimated adult re- 

 turns (Raymond 1979, see footnote 2) of the mix- 

 ture of wild and hatchery populations of juvenile 

 chinook salmon passing Little Goose Dam in 1971, 

 1972, and 1973 were 1.3, 0.6, and 0.4%, respec- 

 tively. While some benefit can be shown when 

 percentage return data from transported groups 

 are compared with only the Rapid River Hatchery 

 returns for 1971 and 1973, only those transported 

 in 1973 showed a benefit when returns were com- 

 pared with estimated percentage returns of adults 

 from mixed wild and hatchery smolts passing Lit- 

 tle Goose Dam. 



When the combined returns of spring and sum- 

 mer chinook salmon were divided into seasonal 

 races (Table 7) and compared for the 3 yr of this 

 study, the benefits or losses from transportation 

 were defined by time. Transport/ control ratios in- 

 dicated that spring chinook salmon received great- 

 er benefit from transportation in 1971 and 1973 

 than summer chinook salmon. Summer chinook 

 salmon appeared to receive more benefit than 

 spring chinook salmon in 1972, but returns from 

 all chinook salmon releases were low in 1972. 



Several factors could be responsible for the dif- 

 ferential in transport/control ratios between 

 spring and summer chinook salmon among the 



years. Probably the most important factor was the 

 timing of seaward migration of the two races of 

 salmon. The race migrating downstream during 

 the most favorable river conditions would receive 

 the least benefit from transport in any particular 

 year. 



Timing of Adult Returns of Chinook Salmon 



Analysis of data on timing of adult returns in 

 comparison with timing of the juvenile seaward 

 migration (Table 8) indicated that the timing of 

 adult returns of chinook salmon to Little Goose 

 Dam was independent of timing of juvenile sea- 

 ward migration (G = 0.518, 0.516, and 0.293: df = 

 1,P<0.05 for 1971, 1972, and 1973, respectively). 

 This is in contrast to what Ebel et al. ( 1973) found 

 in adult chinook salmon returning from groups 

 marked at Ice Harbor Dam in 1968. In this study 

 most of the chinook salmon marked early in the 

 spring migration returned early as spring chinook 

 salmon, and most of those marked late returned 

 later as summer chinook salmon. Perhaps inter- 

 cepting the fish 130 km farther upstream elimi- 

 nated the relation indicated from the earlier 

 study. It is also possible that races of chinook salm- 

 on that exhibited this behavior in 1968 were 

 absent or very low in numbers during 1971-73. 



Table 8. — G-statistic test of relationship between timing of 

 adult returns of chinook salmon to timing of juvenile seaward 

 migration at Little Goose Dam, 1971-73. 



'^Evan Parrish, Hatchery Manager, Idaho Fish and Game 

 Dep., Rapid River Hatchery, Riggins, Idaho, pers commim. 

 1973-76. 



'Early = marked as juveniles from beginning of migration to 5 May. Late 

 = marked as juveniles after 5 May. 



^Prior to 15 June. 



Mfter 14 June. 



"P >0.05. df = 1 ; NS (nonsignificance) indicates timing of adult returns is 

 independent of timing of seaward migration. 



Table 7. — A comparison of adult returns to Little Goose Dam of transported and nontransported (control) spring and summer 

 chinook salmon smolts, 1971-73. Percentage values indicate adult returns from transported group. 



499 



