In the vitamin 8^2''^^^^'^^^°^ ^°^> °° ^^' 

 ficiency syndromes were noted, even when this 

 group was divided after 12 weeks on the depleted 

 diet. Those fish receiving the complete test 

 diet exhibited little difference from those fed 

 the diet without vitamin 8^2" 



In the ascorbic acid deficient group, 

 growth comparable with the controls was ob- 

 served throughout the course of the experiment. 

 The mortality rate paralleled closely that of the 

 control groups at least for the first 14 weeks of 

 feeding. The group as a whole seemed healthy 

 and showed less disease incidence than any other 

 group, except the controls, until the last 2 weeks 

 of the experiment. During the last 2 weeks of 

 feeding, most fish examined in all lots showed a 

 hig^ incidence of Hexamita , myxobacteria, or 

 both. 



The entire course of the experimental 

 feeding period was beset with problems of 

 Hexamita infestation, myxobacterial infection 

 and natural-food problems. The water temper- 

 ature gradually increased from a low of 54° F. 

 to a hig^ of 68° F . during the middle of the feed- 

 ing period. Unfortunately, the temperature 

 remained high (in the low 60 's) until the 16 -week 

 feeding period was terminated. In the mornings 

 the temperature was in the middle 50 's, in- 

 creasing from 7° to 10° F. during each day. Be- 

 cause of the severe disease incidence, repeated 

 prophylactic treatments with pyridal mercuric 

 acetate were given for one hour every two weeks 

 starting at the sixth week of feeding. Undoubt- 

 edly, some adverse physiological effects were 

 experienced by the fish which may have tended 

 to obscure the appearance of specific vitamin 

 deficiency syndromes. 



These experiments show again the neces- 

 sity of having a fish disease -free water supply 

 for conducting critical nutrition experiments in 

 order to prevent the disease symptoms from 

 masking the appearance of the deficiency syn- 

 dromes. The desirability of a more stable or 

 controlled water temperature also manifested 

 itself with the extreme variation in even daily 

 temperatures reflecting severely on the feeding 

 habits of the various groups of fish and on the 

 calculation of the correct dietary intake for each 

 lot. Perhaps more descriptive information of 

 subclinical manifestations of the deficiency 



syndromes will be obtained upon completion of 

 the histopathology investigations of the tissues 

 of fish collected during the course of the experi- 

 ment. 



SUMMARY 



A complete vitamin-test diet successfully 

 used to induce specific water-soluble vitamin de- 

 ficiencies in Chinook salmon was fed to silver 

 salmon for a 16 -week feeding period. Deleting 

 the water-soluble vitamins one at a time from 

 this complete diet caused deficiency syndromes 

 to appear. Under the experimental conditions 

 used, some deficiency syndromes for thiamine, 

 pyridoxine, folic acid, biotin, pantothenic acid, 

 inositol, and choline were induced in silver sal- 

 mon. Inconclusive results were obtained with 

 niacin, riboflavin and vitamin 8^2 deficient diets. 

 No deficiency syndromes were observed for the 

 ascorbic acid deficient lot and since p -amino 

 benzoic acid was not included in the vitamin mix- 

 ture, it also was probably not required. 



Appreciation is expressed to G. Duane 

 Gahimer of the U.S. Fish and Wildlife Service 

 and Daniel C. Coyle, Washington State Depart- 

 ment of Fisheries, for their help in the prelimin- 

 ary hatchery operation, diet preparation, care 

 and feeding of fish. W. C. Ashcraft, the 

 Issaquah Hatchery superintendent, was extremetly 

 helpful, and Brian W . Earp, Washington State 

 Department of Fisheries, generously investigated 

 and checked the fish pathology. The facilities 

 and the fish were supplied by the Washington 

 State Department of Fisheries, and the diet in- 

 gredients and laboratory equipment were furnished 

 by the Western Fish Nutrition Laboratory. 



