REPORT OF THE COMMISSIONER OF FISHERIES. 21 



STUDY OF FISH DISEASES. 



Investigations of a tumorous disease in cultivated fishes which ex- 

 tensively affects Salmonidse, especially trout raised under domestica- 

 tion, have been conducted almost continuously throughout the year. 

 A point has been reached which indicates that the source of the infec- 

 tion or other cause of the disease has been localized, and this means 

 the first step in the formulation of measures required for its eradica- 

 tion in the hatcheries. It is still too early to express a definite opin- 

 ion, but if the present indications should be supported by future re- 

 search, it appears probable that the work will result in a very con- 

 siderable saving to the Bureau by making possible a reduction in the 

 mortality among artificially hatched Salmonid». In respect to the 

 possible relationship of the disease to analogous affections of human 

 beings nothing conclusive can be stated. 



The work has been carried on partly in the experimental aquarium 

 established at the Gratwick Laboratory in Buffalo, and partly in the 

 Craig Brook (Me.) station of the Bureau. The lack of a properly 

 equipped laboratory and experiment station has been seriously felt 

 and is further alluded to in the accompanying recommendations. 



During the year the Bureau has made investigation of several 

 fish epidemics and numerous experiments on the effects of various 

 industrial wastes and pollutions on fish life. This subject is im- 

 portant from the viewpoint of many industries other than the 

 fisheries. 



PACIFIC COAST SALMONID^. 



Investigations concerning the life history and physiology of the 

 Pacific coast salmons were continued during the year, the most inter- 

 esting inquiries being those conducted with reference to the growth 

 and migration of certain species. A large amount of material and 

 data that were gathered is being utilized in the study of the devel- 

 opment and age as recorded in scale structure, and the results thus 

 far obtained demonstrate conclusively that it is possible to determine 

 very accurately the age of our west-coast salmon. 



Certain tagging experiments with the steelhead also yielded very 

 interesting results. A large number of these fish were tagged in a 

 small stream flowing into Monterey Bay and many of them returned 

 the next year to the same place in the stream from which they were 

 originally captured. 



Among other important results of this work is the discovery of a 

 run of chinook salmon in San Lorenzo River, Santa Cruz County, 

 Cal. No run of Chinook salmon had ever before been reported from 

 this stream, and it is evident this run is the result of plants of chinook 

 salmon fry made there in 1906 and 1907. These results coincide 



