*78 American Fisheries Society. 



High mortality is a relative term. To many a practical fish 

 culturist the loss of 25 per cent of the fingerlings has come to 

 be regarded as the normal loss to be expected. On the face of 

 it that loss seems abnormally high. Fingerlings have been 

 dropping away season after season without apparent external 

 signs of disease or without knowledge of the reason why. It 

 seems more than likely that the annual loss in the hatcheries, 

 that is, "the normal loss to be expected," disregarding the loss 

 from epidemics, is referable in a high degree to individual cases 

 of octomitiasis. 



DISTRIBUTION. 



Octomitiasis appears to be a disease of domestication. Al- 

 though the organism which produces it has only recently become 

 known it is not necessarily a new disease. Infection by Octomitus 

 has been found in all of our trout-rearing hatcheries in the State 

 and in three private hatcheries which have come under inspection. 

 It is probably endemic in most of them in this country. Under 

 conditions of artificial feeding and crowding in the hatchery the 

 disease appears to be aggravated, although there is wide varia- 

 tion in the different hatcheries as to the extent of the trouble. 

 The survey of the field for the presence of Octomitus in wild 

 trout has been begun, but with insufficient observation thus far 

 to warrant a generalization regarding its distribution in the 

 wild state. 



TRANSMISSION'. 



The transmission of the organism to fish in the hatchery 

 may be considered from several standpoints. In its adult, active, 

 motile form Octomitus does not persist long outside the in- 

 testinal tract, but forms cysts by rounding up and developing 

 about it a resistant wall which survives desiccation for con- 

 siderable periods. The ordinary motile form, if taken into the 

 intestine of the fish, would hardly survive the digestive juices of 

 the stomach, while the cyst with its resistant wall could reach 

 the seat of infection in the fore-intestine. If such is the case, 

 bits of excrement from infected fish easily explain its transfer 

 from fish to fish. 



If it is found that wild fish are carriers of the organism, the 

 original "seeding down" of a hatchery can be explained from 

 this source. Persistence of the disease in the hatcheries is 



