Only one blueback with a double -fin 

 mark was examined from the commercial catch 

 in 1957. The marked fish was one of a group of 

 51,833 blueback of the 1953 brood that were 

 reared at the Metolius River Hatchery of the 

 Oregon Fish Commission, marked by excision 

 of the adipose and left ventral fins, and liber- 

 ated into Suttle Lake in September 1954. This 

 one marked fish examined was tuberculous. 



this fish was of the 1953 brood and was one of 

 31,000 liberated by the Oregon Game Commis- 

 sion into the Deschutes River. It was not found 

 to be tuberculous. 



The number of steelhead examined are 

 listed in table 8 according to the relative num- 

 ber of acid-fast bacilli observed in the prepared 

 smears. 



In table 8 the number of blueback exam - 

 ined are listed according to the relative abun- 

 dance of acid-fast bacilli observed in the 

 prepared smears . It may be seen that the degree 

 of infection is relatively light compared with the 

 other species. 



Steelhead 



The steelhead trout enter the Columbia 

 in nearly every month of the year and spawn in 

 practically all of the tributaries . The sampling 

 of the species did not commence until June so 

 only the so-called summer steelhead were ex- 

 amined. In general, summer steelhead pass 

 through the lower river from June to October and 

 are destined for tributaries of the upper Colum - 

 bia . Winter steelhead, on which the major 

 emphasis of artificial propagation is placed, pass 

 through the lower river from November through 

 May and spawn in tributaries of the lower river. 

 Samples were taken in each full week of the open 

 seasons in which significant landings were made. 

 Landings from all zones were sampled during 

 the survey. 



The data on tuberculosis in steelhead 

 trout caught by the gill -net fishery in 1957 are 

 shown in table 7. As with the other species, 

 these data are weighted by the number of fish 

 caught to give the estimated number of tubercu- 

 lous fish caught by week and by season. Com- 

 pared with chinook and silver salmon, the 

 estimated percentage of steelhead taken by the 

 fishery that were tuberculous is much lower, 

 although it is somewhat higher than that for 

 blueback. 



Only one double -fin marked steelhead 

 caught by the fishery was examined in 1957. 

 This was a fish marked by excision of the adi- 

 pose and right pectoral fin . It is probable that 



HATCHERY EGG -COLLECTING 

 STATIONS 



Adult fish returning to the various hatch- 

 ery egg-collecting stations of the Oregon Fish 

 Commission were sampled for tuberculosis in 

 1957. The locations of these hatcheries are 

 shown in fig. 1. With few exceptions, the adults 

 returning to the hatcheries include both wild and 

 hatchery -reared fish. In most cases the pro- 

 portion of each is unknown for any particular 

 species at any particular hatchery. 



A sample of 40 livers or more was ob- 

 tained from fish of each species returning to the 

 individual hatcheries; however, in some cases, 

 a lesser number was taken due to the small num- 

 ber of adults appearing at the egg-collection 

 stations or for other reasons. The samples, 

 usually obtained by the hatchery personnel, were 

 taken from the middle portion of the respective 

 runs. Data included with each liver sample in- 

 cluded the fork -length, sex, and species of the 

 fish. Livers of marked fish were taken separately 

 from the sample. 



Five groups of fish were sampled more 

 comprehensively. These were silver salmon re- 

 turning to Klaskanine Hatchery; fall chinook 

 returning to Bonneville Hatchery; and spring 

 chinook, blueback, and steelhead returning to 

 the Willamette (Oakridge) Hatchery. At these 

 hatcheries, livers were taken in a random manner 

 throughout the period of time that the fish were 

 present at the egg-collecting stations . Two of 

 these groups, blueback and steelhead, were of 

 special interest in that they represented the first 

 return of adults of these species to the Middle 

 Fork of the Willamette River . The runs resulted 

 from hatchery liberations of 1953 brood fish from 

 the Willamette Hatchery. 



28 



