FOREST, FISH AXD GAME COMMISSIONER. 1 53 



sources.* In this country a disease of brook trout upon Long Island has 

 been ascribed to a hitherto unknown protozoan. f This was at Northport, 

 and within about nine miles of the present outbreak. In external appear- 

 ance, the marks upon the dying fishes in these two diseases were similar and 

 created a presumption at the outset of their identity. At several other places 

 on Long Island, epidemics have occurred during the past few years which 

 are reported to resemble these, and it is not improbable that in the restricted 

 region of this island the same causes are at work to produce among the 

 many broods of trout which are there held in domestication severe epidemics 

 attended with a high mortality. 



Examination of fresh unstained tissues or blood, of the dying and dead 

 trout, reveals practically no definite knowledge concerning the parasite. 

 Neither are preserved and stained preparations easily interpreted. The bal- 

 ance of evidence points to the presence of Lymphosporidium truttae of 

 Calkins, and the disease is provisionally identified with that caused by this 

 parasite. The reader is referred to Professor Calkins's paper (see reference) 

 for the descriptions and illustrations of the organism itself, while some con- 

 siderations will be here presented on the subject of infections in general 

 among trout, the several causes which combine to produce an epidemic, 

 and the measures which will lessen the chance of the recurrence of this 

 disease in common with others of its type. 



Trout have been for many years raised successfully and without serious 

 losses at the Cold Spring Harbor Station, and, therefore, this outbreak of 

 disease was the result of some unfavorable conditions which had not always 

 obtained, or else of a culmination of such conditions continued back even 

 to the beginning of operations. The water is of apparently excellent quality 

 and has a normal content of dissolved air. There were certain unusual 

 conditions prevailing previous to the outbreak which are of some value in 

 considering its origin. A part of the station grounds including the larger 

 ponds was flooded by the breaking of a mill dam during the spring, many 

 trout were washed out to the harbor and much silt deposited in the ponds. 



* Handbuch der Fischkrankheiten, Bruno Hofer, Muenchen 1904. 



t Report on the recent epidemic among brook trout on Long Island. Gary N. 

 Calkins, Fourth Annual Report, New York Fisheries, Game and Forest Commissioners, 

 i9o8. 



