Moore. — New Species of Parasite in Trout. 75 



hatchery at Bath, N. Y., led the Conservation Commission to 

 inquire into its cause. It had been assumed, because of the ap- 

 parent symptoms of "gill trouble," that the water was low in 

 oxygen. Accordingly, about five years ago, a fountain and flume 

 were introduced into the system of water supply to improve the 

 aeration. There appeared to be temporary relief, yet the losses 

 continued annually to be heavy. The mortality was especially 

 high last season and on the reappearance of the epidemic in 

 April of this year the whole problem at the hatchery was given 

 intensive study. 



Preliminary to the study of the disease a sanitary inspection 

 of the plant and a chemical analysis of the water, including 

 oxygen determinations, were made by experts in these fields in 

 the Commission. Their results, which are appended to this paper, 

 show that the sanitary conditions of the plant are excellent, but 

 a low oxygen content prevails in the water supply, the gaseous 

 oxygen present in water delivered to the hatchery troughs being 

 only 2.10 parts per million, or 18.5 per cent saturation at 9 de- 

 grees Centigrade. 



While it is reasonable to suppose that the annual heavy 

 mortality of fingerlings at the Bath hatchery may be corrrelated 

 with a possible low resistance of the fish due to a deficiency in 

 the oxygen supply, it must be noted that, after the epidemic 

 ceases, the fingerlings, which either escape the infection or ac- 

 quire immunity, thrive remarkably well. Moreover, at other 

 hatcheries, v/here the oxygen relations are notably good, the 

 disease has been observed to approach the nature of an epidemic. 

 That the fatalities were not more serious at the various hatcheries 

 may be attributed to delayed infection or to the presence of other 

 factors and varying practices at the different hatcheries. 



That the disease should be locally diagnosed as "gill trouble" 

 was not unnatural under the circumstances. The swollen ex- 

 posed gills of the sick fish and the apparent efltort in breathing 

 seemed to indicate this as a primary cause of death, particularly 

 since it was known that the oxygen supply approached the criti- 

 cal point for fishes. Persistent and careful study revealed no 

 definite lesions of the gills, excepting that they were somewhat 

 swollen and usually clogged with debris. It was observed, how- 

 ever, that troughs and races carrying approximately the same 

 numbers of fingerlings showed vast diflterences in mortality 



