136 U-S. BUREAU OF FISHERIES 



investigators there is still much to be learned regarding even the best- 

 known disease which will be of great assistance in developing more 

 effective methods of control. Requests for the diagnosis of diseased 

 fish are constantly increasing and considerable time is spent in the 

 routine examination of specimens sent to the Washington office for 

 this purpose. The constantly increasing demand for large trout for 

 stocldng purposes has resulted in a more complete reahzation of 

 the importance of disease in fish-cultural practice. The control of 

 disease is now recognized as one of the most important problems 

 confronting the fish culturist, since the output of his hatchery depends 

 to a very large degree on his success in keeping the fish free from 

 infection. 



In view of the importance of this problem a program has been 

 worked out whereby members of the aquicultural staff make occa- 

 sional visits to hatcheries located within a reasonable distance, for 

 the purpose of detecting the presence of disease and also to furnish 

 advice and assistance in every way possible. Unfortunately, owing 

 to decreased appropriations it was necessary to practically discontinue 

 this service after several months, but enough was accomplished in 

 the brief time it was in operation to demonstrate clearly its value in 

 increasing hatchery production. 



Dr. Frederic F. Fish spent some time at the Fairport (Iowa) station 

 investigating the bass tapeworm with which the brood fish have 

 become heavily infested. It is evident that this parasite constitutes 

 a problem of major importance in bass culture since, when abundant, 

 it seriously interferes with reproduction and may cause practical 

 sterilization of the brood fish. It is believed, however, that by exer- 

 cising proper precautions it will be possible to prevent the young 

 bass from being infected and in this way a brood stock can be built 

 up which will be free from the parasite. It is very evident that 

 under present conditions it is impractical to rely on wild fish for 

 brood stock and that the future success of bass culture depends on 

 hatchery-reared brood fish free from parasites and disease. 



Experiments are being conducted with the object of developing a 

 method of treating trout in pools for external parasites. At present 

 when fish in pools contract gill disease or become infected with pro- 

 tozoan parasites it is necessary to remove them for treatment. It is 

 believed that by the use of very dilute solutions it will be possible to 

 cure the fish while still in the pools and thus avoid the injurious 

 effects of handhng which usually result in considerable mortality. 

 If a successful method of treating the fish can be worked out it will 

 remove the most serious objection to the use of pools or raceways 

 for rearing small fingerlings. 



COOPERATIVE STUDIES OF THE NUTRITIONAL REQUIREMENTS OF TROUT 



During the past summer an agreement was executed between the 

 United States Bureau of Fisheries, the New York State Conservation 

 Department, and the New York College of Agriculture at Cornell 

 University for the purpose of conducting on a cooperative basis 

 experimental studies in fish culture relating especially to fundamental 

 problems of nutrition and pln^siology of fishes. Complementing, and 

 to a certain degree paralleling, studies of fish-feeding conducted at 

 the Bureau's experimental fish-culture stations, the new undertaking 



