PROGRESS IN BIOLOGICAL INQUIRIES, 19 2 7 241 



Sometimes the pectoral fins are attacked first, and may be destroyed 

 almost entirely before the others are affected. This seems to be true 

 most generally of small fingerlings. In still other cases the disease 

 may attack chiefly the caudal fin. 



Usually the first noticeable indication of the disease is a more or 

 less distinct white line along the outer margin of the fin. This 

 white streak moves gradually toward the base of the fin, while at 

 the same time the outer margin of the fin becomes badly frayed. 

 This continues until the entire fin may be destroyed. In late stages 

 of the disease sores filled with a glistening white pus may develop 

 at the base of the fin, and occasionally such lesions occur in the skin 

 some distance from the fin. Due to discharge of the pus into the 

 water, these lesions may appear as small, usually circular depres- 

 sions, which extend for some distance into the underlying muscles. 

 The sides of such lesions are defined so sharply as to look as though 

 a small piece of the tissue had been removed with a sharp instru- 

 ment. The extent to which sores develop at or near the base of the 

 fins depends largely on the size and age of the fish. In very young 

 fingerlings death usually occurs before the tissues at the base of the 

 fins become infected, so that the occurrence of lesions on the body is 

 rare. Larger fish, being more resistant, may live for some time after 

 one or more fins have been destroyed entirely, and therefore there is 

 more opportunity for lesions to develop in the adjoining tissues. 



The bacteria develop not only on the surface of the fins but also 

 penetrate the tissues. Apparently they attack the connective tissues 

 chiefly. In their growth through the tissues the bacteria follow the 

 lymph channels and thus eventually reach the connective and muscu- 

 lar tissues at the base of the fins, where they cause the formation of 

 the sores or ulcers previously referred to. 



The disease can be controlled by dipping the fish in a solution of 

 copper sulphate, but owing to the fact that the bacteria can not be 

 reached so readily by the solution, more treatments-^ are necessary 

 than in the case of the gill disease. Obviously, to be effective the 

 treatment must be applied before the bacteria penetrate the tissues 

 to any depth, as in late stages of the disease they can not be reached 

 by the chemical baths. All fish in which the disease is well advanced 

 should be destroyed, and the rest should be given several treatments 

 with the copper-sulphate solution. 



A visit to the bureau's Drumlin hatchery, near Barneveld, N. Y., 

 disclosed that heavy mortality among fingerling and yearling trout 

 was due to f urunculosis, but that both gill disease and " fin rot " were 

 present and caused a considerable percentage of the mortality. 



During the past year the pathologist was consulted by a number of 

 State and commercial hatcheries regarding mortality from furuncu- 

 losis or other disease. At the request of the American Railway Ex- 

 press Co., preliminary investigations were undertaken to determine 

 the causes of the frequent heavy losses of goldfish during shipment. 

 The express company shipped some fish from Maryland to Washing- 

 ton, D. C, where they were held in cans for several days and then 

 returned to the express company. . The fish were graded into four 

 sizes, and the number allotted to each can was in accordance with 

 usual practice in making commercial shipments. It was found that 

 virtually the entire oxygen content of the water in the cans was ex- 



