EBEL: TRANSPORTATION OF CHINOOK SALMON AND STEELHEAD SMOLTS 



Harbor Dam could have resulted in less stress 

 than that at Little Goose Dam. Further examina- 

 tion of the data, however, implies that the condi- 

 tion of the fish (factor 4) may have been the main 

 factor. Estimated adult returns of chinook salmon 

 to Ice Harbor Dam from fish transported in 1969 

 and 1970 (Slatick et al. 1975) were much lower 

 (0.113-0.581^ ) than recorded from experimental 

 groups released in 1968. The authors attributed 

 the lower returns to stress caused by the place- 

 ment of two new dams (Lower Monumental and 

 Little Goose) in the migratory path of the juveniles 

 and from stress caused by the use of a fish pump in 

 the handling operation. The descaling and delayed 

 mortality percentages in the study at Little Goose 

 Dam indicated that stress in the collection, han- 

 dling, and hauling procedures was a factor. 



Steelhead were not affected in the same manner 

 as chinook salmon in either this study or the ear- 

 lier studies at Ice Harbor Dam. In both studies 

 steelhead returned at a substantially higher rate 

 than chinook salmon. Estimated percentage re- 

 turns to Little Goose Dam of steelhead that had 

 been transported as juveniles ranged from 1.4 to 

 2.6%; returns from releases at Ice Harbor Dam in 

 1969 and 1970 ranged from 0.6 to 1.6%. Since 

 steelhead smolts are larger than chinook salmon 

 smolts, they may have been able to withstand the 

 rigors of collection, handling, and marking; the 

 very low delayed mortality percentages, shown in 

 this study for steelhead, support this reasoning. 



Effect of Transportation on Homing 



The transport/control ratios provide informa- 

 tion on the effect of transportation on homing. For 

 example, if no differential mortality occurred be- 

 tween groups, a steadily decreasing ratio of 

 transport/control numbers from the commercial 

 and sport fisheries below Bonneville Dam to the 

 spawning ground would indicate a loss of homing 

 ability or straying. 



During the 3 yr of study , this type of comparison 

 could only be made from 1971 releases of juvenile 

 chinook salmon because the lower river commer- 

 cial fishery was closed after 1973. A comparison of 

 recovery ratios of adult fish from these releases 

 showed that the transport to control ratios were 

 2.86, 1.65, and 3.95:1 in the commercial fishery at 

 Little Goose Dam and the spawning grounds, 



**Retum to the hatcheries included in computation of 

 transport/control ratio. 



respectively. Although there was a variation in 

 the ratios from the lower river to the spawning 

 grounds, these ratios indicated that ability of 

 transported chinook salmon to home to either 

 their parent stream or Rapid River Hatchery was 

 not seriously damaged by transporting the fish 

 around the seven dams and reservoirs between 

 Little Goose and Bonneville Dams. 



The ratios also imply that hatchery stocks were 

 benefited to a greater degree than wild stocks. 

 When returns to the spawning grounds were sepa- 

 rated from returns to Rapid River Hatchery and 

 separate transport/control ratios were computed, 

 the ratio for wild stocks became 1.5:1 and hatchery 

 stocks, 4.6:1. However, more data are needed re- 

 garding this aspect ( only six fish were recovered on 

 the spawning grounds from releases in 1973) be- 

 fore conclusions can be made on the differential 

 effect that transportation might have on hatchery 

 and wild stocks of chinook salmon. A comparison 

 between the ratio in the commercial fishery (2.8:1) 

 and at Little Goose Dam (1.6:1) also indicates that 

 transported chinook salmon may have been af- 

 fected differently from controls — if one assumes 

 that no differential mortality occurred between 

 control and transported fish as they moved upriver 

 and that wild and hatchery stocks were captured 

 at the same rate in the fishery as they were at 

 Little Goose Dam. Returning adults transported 

 as smolts may have been slightly disoriented or 

 remained for a longer period in the lower river, 

 thus permitting the fishery to take a dispropor- 

 tionate number of transported fish. 



Ebel et al. (1973) found no difference in 

 transport/control ratios from the commercial 

 fishery to the spawning grounds when data from 

 releases at Ice Harbor Dam in 1968 were analyzed. 



Disproportionate straying of adults from groups 

 transported as juveniles would also be an indica- 

 tion that homing behavior had been affected by 

 the transportation. No straying of either chinook 

 salmon or steelhead was observed in the earlier 

 study at Ice Harbor Dam. On the basis of re- 

 coveries of marked chinook salmon in the Des- 

 chutes River, some straying of chinook salmon 

 that had been transported as juveniles occurred in 

 this study. This instance of straying and the varia- 

 tions of transport/control ratios from the fishery to 

 Little Goose Dam indicate that the migratory 

 route lost by collecting the juveniles 130 km up- 

 stream at Little Goose Dam may be of some impor- 

 tance in determining homing behavior. A current 



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