42 U. S. BUREAU OF FISHERIES 



pointed out that while not as conclusive, the results obtained with 

 the buffalofish, bluegills. and bullheads are. so far as thev go. in 

 complete accord with those obtained in the carp experiments. 



In all the lots fed vitamin-deficient diets the mortality was very 

 high, ranging from 45 to 67 per cent in the various lots, while 

 in the controls, consisting of 44 fish, there was no loss during the 

 course of the experiment. Strangely enough all of the fish made a 

 good growth. This may possibly be explained by the fact that they 

 all obtained some natural food, which, of course, contained vitamins. 



The most characteristic symptoms were produced by the lack of 

 water soluble B. Many of the carp fed on a diet containing no B 

 vitamin developed characteristic convulsions after a time. On being 

 alarmed they would dart rapidly to and fro, dashing their heads 

 against the sides of the trough and leaping from the water. After 

 a short time they would stiffen with convulsive shudders and sink 

 quietly to the bottom. Recovery usually took place within a few 

 minutes, after which the fish appeared perfectly normal for a time. 

 The intensity of the paroxysms increased from day to day until the 

 fish eventually died. At different times several fish that had devel- 

 oped con^ailsions were removed and given food containing 10 per 

 cent of yeast. The effect was almost immediate, the fish appearing 

 perfectly normal on the following day. 



Many of the carp given a diet in which only water soluble C was- 

 absent developed white patches on the gills. Such fish invariably 

 died, although there was no evidence of infection by bacteria or other 

 organisms. Although the mortality was high in the case of carp 

 fed on a diet lacking fat-soluble A only, there were no characteristic 

 symptoms and no evidence of infection of the eyes. This is in accord 

 with the experiments on mammals, it being generally conceded that 

 the xerophthalmia which develops is primarily due to failure of the- 

 tear glands to function, as a result of the absence of vitamin A. 



These experiments demonstrate that vitamins are just as essential 

 to fish as to higher vertebrates, but there is still much to be learned 

 regarding the specific effects of vitamin deficiency. It is planned to 

 carry on similar experiments with fingerling trout at the White 

 Sulphur Springs (W. Va.) station, where the food supply can be 

 more efficiently controlled than at Fairport. 



In connection with the investigations at Fairport a series of experi- 

 ments with fingerling trout was undertaken at the Manchester (Iowa) 

 station. The primary purpose of these experiments, which were- 

 carried on by M. C. James, was to develop a more satisfactory diet 

 for use at trout hatcheries. Since the foods usually given trout are 

 believed to be more or less deficient in vitamins, it was felt that 

 possibly much of the mortality at the hatcheries might be primarily 

 due to this cause. The results to date have fully confirmed this 

 view. It has been found that better growth and lower mortality 

 in rainbow fingerlings can be secured by the addition of vitamins A 

 and B to the diet, whether liver or heart. The best sources of these 

 A'itamins are cod-liver oil and yeast. Attempts at substitution of 

 other sources were unsatisfactory. Various mixtures were used, but 

 up to the present no diet has been found to surpass beef heart and 

 sheep liver to which a sufficient amount of cod-liver oil and yeast has 

 been added. The former diet (heart) is the most valuable, showing 



