The Cold 3princr Harbor Epidemic 

 Among" Troat 



By M. C. MARSH, U. S. Bureau of Fisheries. 



IN the spring of 1904 a heavy mortality set in among the older brook 

 trout at the Cold Spring Harbor, N. Y., Station of the New York 



Forest. Fish and Game Commission, and continued until all the year- 

 ling and most of the adult stock had died, a total of some 12,000 fish. 

 The death rate increased rapidly and on the average 40 to 100 dead fish 

 were taken from the ponds each day, while at the height of the mortality, 

 the daily loss reached 500. An effort to check the loss by transferring the 

 trout to live cars in the salt water of the harbor only served to increase 

 the death rate among the trout so moved. 



The disease from which the trout were evidently dying was character- 

 ized, in most of the dying fish, by prominent external lesions, the chief of 

 which was a shallow ulcer of circular or elliptical outline, and variously 

 seated. This ulcer frequentlv involved the skin alone, sometimes eroded 

 the muscular layers, seldom penetrated deeply and was not observed to 

 perforate the abdominal wall. The cheeks and opercles sometimes showed 

 bloody extravasations and ulcerative areas not sharply defined, while the 

 fins and especially the caudal, were often fraved from the same ulcerative 

 process. The region about the eye became the seat of inflammation, 

 and occasionally the bone itself of the opercle had been slightly eaten 

 away. 



The typical ulcer of the disease, while sometimes almost perfectly cir- 

 cular and as sharply defined as if cut by a metal punch, was more often ellip- 

 tical. When young and small it was often surrounded by a black border of 

 pigment cells and large ulcers also sometimes were more narrowly dark 

 edged. Old ulcers were more apt to show a pale border. The presumption 



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