Data on tuberculosis in the samples of 

 salmon and steelhead returning to the various 

 hatchery egg- collecting stations are shown in 

 table 9. These data are listed by degree and 

 incidence for each hatchery. The hatcheries 

 located on tributaries of the Columbia River are 

 listed separately from those located on coastal 

 streams . 



Data on marked fish returning to the 

 various hatcheries are shown in table 10. Some 

 single-fin marks, as well as double-fin marks, 

 are included where the assignment of origin ap- 

 pears to be valid. 



The data on several groups of marked 

 fish originating from Oregon Fish Commission 

 hatcheries are of interest. It may be noted in 

 tables 5 and 10 that none of the 49 Ad-LV marked 

 silvers caught by the fishery or returning to 

 Sandy Hatchery were tuberculous. In contrast, 

 32 of 41 Ad-RV marked silvers caught by the fish- 

 ery or returning to the hatchery were tuberculous. 

 As young fish of the 1954 brood at Sandy Hatch- 

 ery, both groups, made up of approximately 

 16,000 fish each, were fed the same diet for the 

 initial 2-month feeding period. This initial diet 

 contained untreated salmon viscera, beef liver, 

 and meal. During the next 9 months, one group 

 (Ad-RV) was fed the standard hatchery diet, 

 which contained approximately 60 percent un- 

 treated salmon viscera. The other group (Ad- 

 LV) was fed an experimental diet containing no 

 salmon products. The difference in the incidence 

 of tuberculosis between the two groups upon their 

 return to the fishery and to the hatchery was con- 

 sidered by Wood (1958) to be strong evidence that 

 tuberculosis in hatchery- reared silver salmon is 

 greatly influenced by the fish-cultural practice 

 of feeding untreated salmon products . 



The experiment was repeated using 1955- 

 brood silver salmon at the Sandy Hatchery. The 

 diet during the initial 2 -month feeding period and 

 the standard hatchery diet (fed to fish marked 

 Ad-LMax) again included untreated salmon vis- 

 cera. The experimental diet (fed to fish marked 

 Ad-RMax) did not contain salmon products. As 

 can be seen in tables 5 and 10, 1 Ad-LMax 

 marked silver and 4 Ad-RMax marked silvers 

 returned as jacks (precocious males). One fish 

 in each group was found to be tuberculous. The 

 return of these two groups as adults in 1958 



will furnish additional information on the feeding 

 of untreated salmon products in the diet. 



Another point of interest is that it may 

 be noted in tables 2, 9, and 10 that the incidence 

 of tuberculosis in marked chinook originating 

 from Bonneville Hatchery is much higher than 

 that noted in unmarked chinook returning to Bonne- 

 ville Hatchery. This was noted previously by 

 Wood and Ordal (1958) and was thought to be 

 primarily the result of marked chinook being 

 reared at the hatchery for a longer period of time 

 than the unmarked. Chinook of the 1952, 1953, 

 and 1954 brood years that were marked were held 

 at the hatchery longer than chinook of the same 

 brood years that were released unmarked. In 

 addition, it may be noted in table 10 that marked 

 chinook originating from several other hatcheries 

 entered Tanner, Eagle, and Herman Creeks. 

 Straying of chinook originating in other tributaries 

 into streams in the Bonneville area may account 

 for part of the difference in the observed in- 

 cidence of infection between marked and unmarked 

 chinook . 



Wood and Ordal (1958) previously noted 

 that steelhead heavily infected with tuberculosis 

 were generally smaller than those lightly or non- 

 infected. A similar relationship was noted in 

 other species examined during the 1957 survey. 

 In table 11 are shown comparisons of average 

 fork lengths of lightly (or non- infected) and heavily 

 infected fish. Lightly or non-infected fish were 

 those whose liver smears were rated 1, 2, or 

 negative according to the arbitrary rating system 

 discussed earlier. Heavily infected fish were 

 those whose liver smears were rated 3, 4, or 5. 

 Certain criteria were used in selecting the groups 

 for size comparison in table 1 1 . Only groups 

 that consisted of fish of the same age and for 

 which there were at least 20 fish, by sex, in both 

 the heavily and lightly infected (or non -infected) 

 categories were included. 



On the basis of Student's t^test, the fork 

 lengths of heavily infected fish were significantly 

 different (at the 5 percent level) than those of 

 lightly or non-infected fish, except for three 

 groups. Those not found to be significantly differ- 

 ent were Ad-RP marked falls from Bonneville 

 Hatchery and both male and female blueback from 

 Willamette Hatchery. 



29 



