22 U. S. BUREAU OF FISHERIES. 



hours, during which time it is stirred constantly. When cooked 

 the food resembles granulated yellow cornmeal, and when introduced 

 into the ponds and troughs it does not discolor the water. 



TEST OF COPPER SULPHATE FOR ERADICATION OF FUNGUS. 



The great difficulty experienced in preventing the development 

 and growth of fungus on crappie held for distribution during the 

 summer months impelled the district supervisor in charge of the 

 Mississippi River rescue work to test the copper-sulphate treatment 

 in an effort to find a cure for the trouble. Owing to the extreme 

 weakness of very small crappie and sunfish in intensely warm 

 weather, it was found that they would not survive even a weak solu- 

 tion of the chemical, those used in the test perishing in large num- 

 bers when subjected to it. The results demonstrated that it might 

 be successfully applied to fishes of larger growth and to the stronger 

 individuals among the younger fishes, and also that it is valuable for 

 disinfecting and cleaning the troughs in which fish are held. Its use 

 for such purposes will hereafter be resorted to at the holding and 

 distributing stations in the rescue fields. 



In this connection too much stress -can not be laid upon the need 

 for exercising care in the liandling of fish to avoid abrasions, which 

 serve as avenues of access for bacteria. In landing seines in the 

 rescue fields special effort is made to prevent hauling the fish over 

 low muddy places, thus filling the gills with mud. For the infection 

 work, also, only the larger and stronger fishes are selected as hosts,, 

 all small and weak specimens being carefully culled out. 



PARASITIC AFFECTION IN WHITEFISH JARS. 



In connection with the parasitic affection that caused so much 

 trouble in the whitefish jars at the Cape Vincent (N. Y.) station 

 during the past season, it is the opinion of the bureau that the heavy 

 losses sustained were very largely the result of the additional hand- 

 ling required in order to remove the growth from the jars. In in- 

 vestigating the underlying causes of a heavy loss of shad eggs at 

 Windsor, Conn., Doctor Mitchell, of Brown University, found that 

 a very large percentage of the loss was due not to lack of fertilization 

 but to scratches and abrasions on the surface of the eggs. The raw 

 surfaces caused by the abrasions formed a fertile ground for the 

 multiplication of bacteria, and later on a white mold appeared, 

 quickly coating the eggs. It is quite possible that the heavy mor- 

 tality experienced in the incubation of whitefish and cisco eggs may 

 be traced to injuries to the shell, many of them being caused by the 

 constant screening and washing of the eggs. This may also explain 

 the higher percentage of hatch attained by fishery employees of tlie 

 State when using an inverted funnellike bottom on their jar tubes. 

 The effect of this arrangement is to spread out the intake flow of 

 water, thus imparting a slow movement to the eggs. When eggs in 

 circulation are thrown violently against the jar bottoms they are 

 liable to become more or less scratched, especially if the jars contain 

 particles of iron rust, which is often the case. Heavy losses of 

 brook-trout eggs have frequently been noted when they are massed 

 during the expansion period. In the process of separating the eggs 



