Of academic interest is the fact that we are dealing with a virus 

 that affects an aquatic vertebrate. Only a few such viruses are known 

 or described at the present time. The virus diseases of fish are possibly 

 the best documented of the virus diseases of aquatic vertebrates, but even 

 so, there are comparatively few published reports of such diseases. Since 

 virus diseases of fish have been reviewed recently (Watson, 19!?u), no 

 references will be made to these reports since they seem to have no direct 

 bearing on the present problem. 



The objectives of this investigation were to describe the epizootiology 

 and etiology, to determine the efficacy of chemotherapy and the effect of 

 physical factors on the infectious agent. Despite the fact that there were 

 and still are many points left undetermined and the evidence gathered was 

 not always conclusive, sufficient information of interest was obtained to 

 warrant the presentation of this interim report. A comprehensive study of 

 this virus disease is currently in progress. 



This report deals only with the epizootics which occurred at the five 

 salmon hatcheries in the State of Washington, which are situated in widely 

 separated parts of the state (see fig. l): 



Cook ) 



Entiat ) 



Leavenworth ) U. S. Fish and Wildlife Service Hatchery 



Winthrop ) 



Issaquah Washington State Department of Fisheries Hatchery. 



Each year, the normal procedure has been to trap and spawn fish in 

 local streams in late September and early October, to hatch the eggs in 

 hatchery troughs, and to rear the fry and fingerlings in troughs until 

 the following April or sometimes as late as July. At that time, the majority 

 of the fingerlings have been moved to outside rearing ponds, remaining there 

 until the fall, when they have been planted in a lake having an outlet to 

 the ocean. At the Winthrop and Cook hatcheries, however, the majority of 

 the sockeye salmon were held through their second winter in rearing ponds 

 or raceways before they were released into tributaries of the Columbia River. 



The eggs were spawned from adults in September and hatched in December 

 or January, but the fry did not begin to feed for an additional 30 days . 

 The fingerlings were normally fed a diet consisting of beef, hog, and fish 

 products. 



As it was often necessary to supplement an established salmon run or 

 even to establish a new run, eggs were often transferred from one hatchery 

 to another in a different area, reared there, and subsequently released 

 into lakes and streams in that area. 



