A REPORT OF PROGRESS ON THE STUDY 

 OF TROUT DISEASES. 



By Emmeline Moore, 

 N. Y. State Conservation Commission. 



This progress report carries forward the studies that were 

 begun last year and reported upon before the American Fish- 

 eries Society in a paper entitled "Giardiasis of Trout." It 

 happens that the organism producing the disease is not 

 Giardia, but Octomitus, a near relative whose full name, Oct- 

 omitus salmonis, has been duly entered in the annals of the 

 society. Its name has been changed to satisfy taxonomic re- 

 quirements. Its habits, however, remain as verminous as 

 before. 



Following the reading of my paper last year on the presence 

 of Octomitus in the New York State hatcheries, it transpired 

 that Dr. Davis, Pathologist of the U. S. Bureau of Fisheries, 

 was studying the organism, also, in the Virginia and Tennessee 

 hatcheries. Information has come recently of its presence at 

 hatcheries in three other states — Iowa, New Jersey and Mas- 

 sachusetts. Such spottiness may be interpreted to mean a 

 much more general distribution in the hatcheries of the eastern 

 states, where its recognition awaits only greater discrimina- 

 tory power in determining the reasons for mortality, now 

 often generously charged off as "normal loss." 



Before proceeding with my later findings, let me recall 

 briefly for the sake of orientation the more important features 

 of last year's report. 



It was found that Octomitus is a minute, protozoan para- 

 site in the intestine of trout, that it is common under hatchery 

 conditions, and that it is the cause of serious epidemics ac- 

 companied by high mortality. It was found, also, that all 

 species of trout are susceptible to the disease, the susceptibility 

 of brook trout over other species being pronounced. 



The most significant and important information proceeding 

 from the studies last year, and this refers both to Dr. Davis' 

 work and my own, bears on the explanation of the mechanism 

 of the disease. It is now known with a fair degree of cer- 

 tainty what m.akes the fish die, and knowing this neither time 

 nor money need be wasted in doctoring symptoms. 



In advancing to the report of progress I must beg your 

 indulgence in presenting unfinished work. It may not be en- 

 couraging to point out that perhaps a not less difficult or- 



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