446 U. S. BUREAU OF FISHERIES 



columnaris. This organism, known to cause serious losses among 

 l)ass, craj)pie, sunfish, etc., when they are handled in warm weather, 

 has not previously been reported among aquarium fish. It aifects 

 tropical fish chiefly during shi])nient. Evidently as the result of 

 injuries caused by bum])ing against the sides of the can, the lower 

 jaw becomes infected, tlie infection advancing along the floor of the 

 mouth until it reaches the gills. This bacterial growth forms a white 

 felt-like mat from which the disease derives its name. The disease 

 can be easily controlled in early stages by treatment with a dilute 

 solution of copper sulphate or other disinfectant. 



It is now evident that an attempt to eradicate furunculosis at the 

 Leetown (W. Va.) experimental hatchery has been entirely successful. 

 During the summer of 1934 several lots of browm and brook trout 

 yearlings developed the disease. Immediately all fish in the infected 

 lots were destroyed and the pools disinfected witli chlorine gas. In- 

 asmuch as no signs of furunculosis have appeared at this station since 

 that time it is evident that the disease was completely eradicated. 

 This case is of special interest since it demonstrates tliat, if taken in 

 time before it has become established, furunculosis can be stamped 

 out at a hatchery without a significant loss of fish. 



The investigation into the causes of "blue-sac" were continued at 

 the Leetown station by E. W. Surber. It was suggested that thei 

 trouble might be due to the high free carbon dioxide content of the 

 hatchery water supply (about 44 parts per million). Accordingly a 

 series of experiments was conducted to investigate the relation be- 

 tw'een the acid-base equilibrium and the health of trout. It was 

 found tliat : 



1. Raising the free carbon dioxide content of the v/ater to 60.7 — 

 62.1 parts per million resulted in a decreased hatch, and an increase 

 in the number of deformed fish. 



2. Brook trout eggs in soft water can develop normally in rela- 

 tively high concentrations of free carbon dioxide (39 p. p. m. at 

 Ogletown, Pa., 42.03 p. ]). m. at Lewistown, Md.). 



3. Blue-sac was not nearly so evident in water neutralized with 

 sodium hydroxide, but since the general effect of this chemical Avas 

 otherwise so deleterious tliere appears to be no advantage in its use. 



4. The addition of sufficient caustic soda to neutralize most of the 

 free carbon dioxide in the water is injurious to brook trout eggs, 

 reducing the hatclied fry to about 28 percent or less of the original 

 number. 



5. Brook trout eggs are more sensitive to the chemical changes 

 brought about by the addition of caustic soda than are rainbow eggs, 

 which in earlier experiments were either unaffected or benefitecl by 

 its addition. 



The functions of the Disease Service were greatly expanded during 

 the year, and a large number of specimens submitted by Federal, 

 State, and commercial hatchery men were examined and diagnosed at 

 both the Washington and Seattle laboratories. Altliough in most 

 cases the service is limited to the examination and diagnosis of pre- 

 served material, it has been of great assistance in enabling fish cul- 

 turists to adopt proper control measures before epidemics were so far 

 advanced as to render such measures ineffectiv^e. 



