SOME FISH-CULTURAL NOTES, WITH SPECIAL 

 REFERENCE TO PATHOLOGICAL PROBLEMS 



By Charles O. Hayfobd 

 Superintendent, State Fish Hatchery, Hackettstown, N. J. 



A fish culturist, operating on a large scale, is confronted with 

 many problems, but he also has many remedies in his own back yard 

 with which to combat these difficulties. In the summer of 1919 the 

 Fish and Game Commission of New Jersey set aside a small sum of 

 money to be used for experimental purposes, as directed by the writer, 

 for overcoming certain difficulties which it was believed could be cor- 

 rected. Investigations have been conducted by Dr. George C. Em- 

 body, assisted by Frederick Tresselt, and Professor W. T. Foster, 

 assisted by Robert W. Hodgson. A brief resume of some of these 

 investigations follows. 



FEEDING AND DISEASES OF TROUT 



Experiments were carried on during the summer of 1920 to de- 

 termine the value of the various artificial and natural foods used for 

 trout at the Hackettstown Hatchery. These experiments clearly 

 demonstrate the value of natural food in the diet of hatchery trout 

 together with the relative importance of the artificial food combina- 

 tions.^ 



The production of the greatest possible number of fish through 

 the elimination of all factors detrimental to the increase of the same, 

 is the object of every fish culturist. To accomplish this, a careful in- 

 vestigation of each of these factors is necessary. The greatest re- 

 duction in the number of fish, under hatchery conditions, is brought 

 about by disease. Each individual hatchery has its own problems, 

 although more or less general conditions prevail throughout. In this 

 hatchery we have been confronted with two important diseases, one 

 protozoan and the other bacterial. The protozoan disease, namely, 

 Ichthyophthirius multifilis, was present during the seasons previous to 

 1920. It affected the rainbow trout. This is not recognized as a 

 serious trouble, in view of the fact that a very specific cure is known, 

 and once the diagnosis is made, the disease can be eliminated. 



The case is somewhat different with the other disease, which is 

 more or less common throughout the country. It is of bacterial 

 origin and is characterized by the development of gray spots on the 

 head in the region of the cerebral hemispheres, followed by an appar- 



^ Transactions, American Fisheries Society, Vol. L, pp. 251-256, 1920. 



97 



