FISHERY BULLETIN: VOL. 78, NO, 2 



Table 2. — Mean mortality of juvenile chinook salmon and steel - 

 head during transport from Little Goose Dam to release loca- 

 tions downstream from Bonneville Dam, 1971-73. 



Table 3. — Mean delayed mortality of samples of juvenile 

 chinook salmon and steelhead taken from marked groups 

 transported from Little Goose to below Bonneville Dam. Fish 

 were held from 48 to 72 h after transport. 



transported smolts released and correspondingly 

 reduced adult returns from transported groups. 

 Control groups may have been less affected be- 

 cause of the shorter transport time (1 h vs. 6 h). 

 However, the assessment of benefits or losses ob- 

 tained from transport of salmonid smolts must 

 include this mortality. Release totals were there- 

 fore not adjusted for either transport or delayed 

 mortality. It was noted that over 90% of the dead 

 fish in the delayed mortality group had obvious 

 signs of descaling or injury. 



Measurements of descaling (fish with >10% of 

 the body area descaled) of chinook salmon smolts 

 that were recorded during the marking process 

 varied from to as high as 50% of the individuals 

 observed. The average annual descaling rate was 

 16.6% in 1972 and 19.6% in 1973. Incomplete 

 records of descaling measurements made it impos- 

 sible to determine the average rate of 1971. De- 

 scaling of steelhead was substantially less than 

 descaling of chinook salmon; the overall average 

 for 1972 and 1973 was <1%. It was determined 

 from other studies being conducted that most of 

 the descaling was caused by experimental diver- 

 sion screens being tested in the turbine intakes 

 (Ebel et aU°). 



There was a relation between descaling rate and 

 delayed mortality. Steelhead were less descaled 

 than chinook salmon and had much less delayed 



'"Ebel, W. J., R. F. Krcma, and H. L. Raymond. 

 1973. Evaluation of fish protective facilities at Little Goose 

 Dam and review of other studies relating to protection of other 

 salmonids in the Columbia and Snake River, 1973. 62 p. 

 Northwest and Alaska Fisheries Center, Natl. Mar Fish. Serv, 

 NOAA, 2725 Montlake Boulevard East, Seattle, WA 98112. 

 (Contract DACW68-71-0093, Progress Rep. to U.S. Army Corps 

 of Engineers, Portland, Oreg.) 



mortality than chinook salmon. It appears that if 

 the injury that occurred during diversion and 

 handling could be eliminated, survival of trans- 

 ported chinook salmon could be substantially im- 

 proved. 



Returns of Adult Experimental Fish 

 to Little Goose Dam 



A comparison of ratios of transport and control 

 percentage returns of adults to Little Goose Dam 

 from releases of chinook salmon and steelhead for 

 the 3 yr of this study (Figure 2) indicated that 

 survival of both species was substantially in- 

 creased in 1973 by transporting the fish to the 

 Dalton Point and Bonneville Dam release sites; 



The percentage increase in survival varied from 

 year to year and, I believe, was dependent primar- 



16 



14 



r CHINOOK SALMON 



1971 1972 



'' □ Control 

 / 5)5 Transport 







n 



n a 



1973 



n 





o 



Q. 



N= 52 266 



Ratio=1.6:1 



16 r steelhead 



1971 



14 



V 



6 - 



n 







N= 199 811 



Ratio=1,7;1 



25 89 



Ratio=l.l;l 



1972 



nJ. 



20 502 



Ratio=15.4:l 



1973 



^ 



n 



I 



132 664 



Ratio=3.25;l 



61 1225 

 Ratio=13.4:1 



Figure 2. — Comparison of ratios of adult percentage return to 

 Little Goose Dam from control and transported juvenile chinook 

 salmon and steelhead. (Returns from Dalton Point and Bonne- 

 ville Dam releases combined.) Percentage return of controls was 

 set at unity for each year and species; the increase (transport 

 percentage return -^ control percentage return) is shown by 

 darkened bar. 



496 



