TREATMENT OF FUNGUS ON FISHES IN CAPTIVITY. 



By L. B. SPENCER, 

 Department oj Zoology and Nature Study, New York A quarium, New York City. 



A large specimen of brook trout (Salvelinus fontinalis) , which was caught 

 with a hook in Sunapee Lake, New Hampshire, was received at the New York 

 Aquarium in the spring of i8g6. The trout had a wound on the head. A few 

 days after being placed in an exhibition tank fungus appeared on the wound. 

 The writer treated the disease by applying salt water from the bay, which is 

 pumped into the aquarium. A hose was used, the end being kept near the 

 head of the trout, so that the stream of salt water reached the wound. This 

 operation was repeated until the fungus disappeared. The wound healed and 

 the fungus did not again appear. 



The use of salt water has been continued in the treatment of the fishes. If 

 the water in the bay is not of sufficient sal tn ess to cure fungus, I use enough 

 rock salt to increase the specific gravity to near 1.028, which is about the specific 

 gravity of ocean water. Most of our fresh-water fishes will endure this treat- 

 ment for a time, but it is necessary to keep watch on some species, or they may 

 die if the salt water is used too long. 



The usual method employed is to draw the fresh water out of the tank to 

 about 10 or 12 inches in depth, or perhaps less if the fishes are not frightened, 

 stopping the inflow of fresh water at the time. The tank is then filled with salt 

 water. By this method the fishes rareh', if ever, appear to suff'er any incon- 

 veniencQ, as the change from fresh to salt water is gradual. When necessary 

 to use rock salt, this is put into the tank before running in the salt water, as the 

 current aids in dissolving it. The water need not be kept in circulation in the 

 large exhibition tanks during the treatment unless one has plenty of salt water 

 to waste; the stream may be cut off for a time, but it is necessary to keep watch 

 on the fishes; as soon as any uneasiness is shown the fresh water should be 

 turned on. It is often necessary to repeat this treatment each day in order 

 to effect a cure. 



In the year 1907 and the winter and early spring of 1908 the Croton water 

 was in such condition that fungus was more prevalent, gave more trouble, was 



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