ent loss of balance, causing a spiral whirling. Death generally occurs 

 shortly after this stage is reached. The fish affected are those in their 

 first year, from May to September, which for the Hatckettstown 

 hatchery would mean fish from 1^^ to 4 inches in length. Both 

 brook and brown trout were affected, but the brook trout to a greater 

 extent. 



The two possible sources of this organism are the water and the 

 food. In view of the fact that this disease, as far as known, is 

 not present among fish in the native streams, the possibility of the 

 transmission of the organism by water may be eliminated. The 

 examinations of the various foods such as beef liver and sheep plucks 

 show the presence of organisms not unlike those isolated from the 

 diseased fish. The study of these organisms has not been carried 

 on to a sufficient extent to show that they are identical, but it sug- 

 gests a possible relationship. It was thought that the presence of dis- 

 solved gases such as CO^ and O might be looked upon as a very 

 important contributing factor in the loss of fish in the hatchery, but 

 a series of experiments carried on in the laboratory has shown this 

 factor is negligible. No noticeable difference appeared between equal 

 numbers of fish held in two ponds, one showing a maximum of CO' 

 and the other its absence. 



The substitution of natural food such as Asellus and maggots 

 for artificial food, as beef liver, was the next logical step. Since, 

 under natural conditions, the fish subsist entirely on insect food, it 

 appears that there must be a certain something, such as a vitamine, 

 which is present in the natural food and lacking in the artificial. This 

 vital substance apparently has an inhibitory effect upon the offending 

 organism within the body of the fish. Experiments have shown that 

 when the disease appears in the hatchery a change of diet to natural 

 food has checked its further progress. On the return to the previous 

 food, immunity continues for from four to five weeks or more. This 

 has been worked out with both brown and brook trout but more 

 especially with the brook trout. Some aquatic insects seem to possess 

 greater germicidal properties, while another type of insect food pos- 

 sesses greater nutritive value. A combination of two, when more 

 scientifically worked out, may solve the problem of loss of fish by 

 this disease, as was indicated by feeding experiments carried on 

 during the summer of 1920. The whole problem narrows down to 

 one of diet, but without doubt the diet would have to be modified as 

 required by the conditions at the different hatcheries. Each fish cul- 

 turist would therefore have to work out his specific salvation based 

 on his own conditions, but according to general facts. 



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