Department of Fisheries Issaquah Hatchery. 

 This vitamin level was fed in order to deplete 

 any large storage of water-soluble vitamins by 

 the fish . At the end of two weeks the fish were 

 randomly divided into 13 groups and placed in 

 standard screen-covered hatchery shallow 

 troughs. Each group was fed a diet deficient in 

 only one of the 11 water-soluble vitamins and 

 the growth was compared with two control lots 

 fed the complete vitamin-test diet. The fish 

 were fed three times daily, six days weekly with 

 no ration offered on Sundays . The food was 

 presented to the fish by grating small cubes of 

 the ration over the water in such a manner that 

 the food presented was eaten in approximately 

 one minute . 



The fish were weighed biweekly accord- 

 ing to a standardized experimental technique 

 (Burrows, Robinson and Palmer, 1951; Halver 

 1957a) and a random sample of five fish was 

 taken for subsequent histopathological analysis. 



Each group was under close examination 

 for the appearance of vitamin deficiency syn- 

 dromes listed for fish (Halver 1957a; McLaren 

 et al . 1947; Wolf 1951). Dead and moribund fish 

 were removed, recorded daily and were exam- 

 ined microscopically for any indication of the 

 presence of fish pathogens. 



When the growth pattern of any of the test 

 diets differed significantly from the control or 

 when more than 20 percent of the population had 

 died, the remaining population of the test group 

 was divided, one -half fed the complete diet and 

 the other half continued on the vitamin -deficient 

 diet until the end of the experiment or the total 

 loss of the population. If that portion of the pop- 

 ulation fed the complete diet recovered from the 

 symptoms, it was then felt that the malady was 

 directly due to the lack of the vitamin in question 

 and that silver salmon required this vitamin. 



The regular hatchery water supply from 

 Issaquah Creek was used. The water to the in- 

 dividual trough was screened through a 64-mesh 

 screened box to eliminate as much as possible 

 the natural food that might come in through the 

 water supply. Finer mesh screen was tried but 

 this had a tendency to plug and overflow subse- 

 quently cutting off the water supply to the 

 experimental fish. 



Throughout the experiment many pathojren- 

 ic diseases were apparent. The two encountered 

 most often were "cold water disease" and "Octo- 

 mitus" . The effect of the pathogen certainly 

 influenced the results, and it was impossible to 

 evaluate growth and mortalities critically. 

 Growth curves of the deficient groups were plotted 

 however, and can be generally compared with the 

 growth and mortality rates of the two control lots 

 fed the complete vitamin-test diet (figs.l ana 2). 



RESULTS AND DISCUSSION 



The two control groups gained weight con- 

 sistently. There was little if any significant 

 difference between the two. This group suffered 

 approximately 50 percent loss over the 16 -week 

 period but all mortalities were heavily infected 

 with Hexamita salmonis and/or myxobacteria. 

 The greatest mortality occurred during the fourth 

 week. A summary of the specific vitamin de- 

 ficiency syndromes observed in the various lots 

 of fish was tabulated in table 2. 



The diet used as the control ration for 

 this study contained approximately 70 percent 

 protein. Subsequent work has indicated that 

 about 50 percent protein might have been a more 

 desirable level for rapid growth with fish living 

 in this temperature range (DeLong, Halver, 

 Mertz 1957). At the time the experiment started, 

 however, this information had not yet been con- 

 clusively demonstrated and it was decided to use 

 the complete vitamin-test diet which did produce 

 near normal growth in chinook salmon for a time 

 period sufficient for the development of water- 

 soluble vitamin deficiency syndromes. For a 

 similar reason, the protein component of the 

 diet was supplemented with methionine and 

 tryptophan even though some evidence had been 

 accumulated that these amino acid supplements 

 to this diet might not be needed for satisfactory 

 growth. High levels of tryptophan would, in 

 addition, probably interfere with the development 

 of severe nicotinic acid deficiencies but since the 

 tryptophan requirements of fish were not known, 

 and this diet had grown chinook salmon, trypto- 

 phan was added. 



The thiamine deficiency group compared 

 favorably with the control groups for the first 

 12 weeks of the experiment. After 12 weeks 



