years was presumably influenced by reduced 

 production as a result of reduced escapement, 

 but values in figure 7 are based on return per 

 pound of fish released and are independent of 

 escapement. Furthermore, returns for brood 

 years since 1952 have been given increased 

 protection by a closed fishery above Bonne- 

 ville Dam, and no adjustment has been made 

 for the effects of this closure. It is likely that 

 the downward trend is somewhat exaggerated 

 by factors unrelated to production, but none 

 of the factors considered here, separately or 

 collectively, can account for the magnitude of 

 this trend. 



FACTORS COINCIDENT WITH CHANGE IN 

 PRODUCTION RATE 



Any attempt to study causal relationships 

 influencing a severe time trend such as is 

 exhibited in figure 7 usually requires controlled 

 experimentation. In the present investigation 

 little more can be done than to list observed 

 factors which are coincident with the period of 

 this trend. Work by specialists in fields re- 

 lated to any such factors has been examined 

 to determine whether or not observed factors 

 are possible causes of a decline and therefore 

 merit future investigation. No extensive cover- 

 age of the literature has been made. 



Incidence of Infection with Acid-Fast Bacteria 

 (Tuberculosis) 



Infection with acid-fast bacteria, commonly 

 called tuberculosis, was first observed in 1952 

 by Wood and Ordal (1958) in adult chinook 

 salmon at the Bonneville Hatchery. The infec- 

 tion since then has been noted at other Columbia 

 River hatcheries in varying degrees of in- 

 tensity. Ross, Earp, and Wood (1959) found the 

 disease at Spring Creek Hatchery in 1957. Of 

 a total of 300 random liver samples collected 

 from normal-appearing fish, 2.3 percent 

 (7) were found to be infected with acid-fast 

 bacilli. Ten liver specimens were collected 

 from abnormal-looking salmon, and nine were 

 found to be diseased. During the 1957 com- 

 mercial season in the Columbia River, a total 

 of six marked fish (anal-right ventral) from 

 the 1953 Spring Creek Hatchery brood were 

 examined. Five of these showed no indication 



of acid-fast bacilli in liver smears, and one 

 showed only a slight infection (Wood, 1959). 

 Random samples were again collected at Spring 

 Creek Hatchery in 1958 and 1959." The in- 

 fection increased to 35 percent in 1958. In 

 1959 it was possible to obtain a random sample 

 of unmarked fish and a separate sample of the 

 marked fish. The unmarked fish showed a 23.5 

 percent infection (11 of 46), whereas 52 per- 

 cent (77 of 148) of the marked fish were in- 

 fected in varying degrees. 



The increased rate of infection for marked 

 over unmarked fish at several hatcheries gave 

 early indication that the disease was probably 

 of hatchery origin since wild fish may con- 

 tribute to the unmarked returns. Studies have 

 shown that the longer the fish are reared and 

 fed in the hatchery, the higher the percent 

 infection (Wood and Ordal, 1958). The causa- 

 tive agent has been shown to be in infected 

 salmon carcasses and viscera used in the diets 

 of young fish in the hatchery. 



This disease is known to affect normal sexual 

 maturation and growth. Wood (1959) demon- 

 strated a significant reduction in the average 

 length of heavily infected fish over lightly or 

 noninfected fish. Significant differences in 

 length were shown for spring chinook of known 

 age and steelhead at the Willamette Hatchery, 

 and a silver salmon at Klaskanine Hatchery. 



Coagulated Yolk Disease 



Outbreaks of coagulated yolk disease (white- 

 spot) have been reported by Johnson." In the 

 4 brood years covered in his report, 1953-56, 

 mortality at Spring Creek Hatchery varied 

 from about 1 percent in 1954 and 1956 to 15 

 percent in 1953. Mortality in 1955 was 5 per- 

 cent. In 1959 a mortality of 3 to 5 percent was 

 attributed to coagulated yolk. The mortalities 

 in the 1957 and 1958 brood years were about 

 1 percent.^ It is of interest to note that the 



" A. J. Ross. U.S. Fish and Wildlife Service, un- 

 published data. 



" Harlan E. Johnson. Coagulated yolk disease in fall 

 chinook salmon at Lower Columbia River Hatcheries, 

 Typed report to Regional Director, U.S. Fish and Wild- 

 life Service, Portland, Oregon. September 4, 1957, 6 p. 



^ Data for the 1957, 1958, and 1959 brood years were 

 obtained from Harlan Johnson. (Personal communi- 

 cation.) 



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