FOREST, FISH AND GAME COMMISSIONER. 1 57 



Those far advanced in the disease will die, others will recover and the yet 

 uninfected fish will be able to avoid taking up infection. These results are 

 brought about both by diluting the infection and by an increase of resisting 

 powers due to the natural conditions. A shallow stream of rather rapid 

 flow is of course more favorable than a sluggish one. 



Xo one measure or single specific can be recommended as sufficient to 

 insure with certainty against this and similar diseases, nor to prevent with 

 certainty their recurrence. Avoidance of overcrowding is necessary, is a 

 condition precedent to freedom from such diseases. The positive measures 

 which are practicable and which decrease the chances of infection relate to 

 disinfection in connection with impervious pond construction. Disinfection 

 of ponds consists in killing the organisms of disease which, especially during 

 and after the course of the disease, are located within the ponds. If they 

 are of wood, earth or gravel or any permeable material, the difficulty of 

 disinfection is increased and it is not easy to make sure of its thoroughness. 

 If of cement, or masonry with a cement finish, both sides and bottom, the 

 organisms have only a free exposed surface upon which to locate and here 

 they may be readily reached and killed by various chemical agents. Such 

 ponds doubtless protect to some extent from the original access of infection, 

 from the first attack which will come sooner or later to most trout ponds, 

 but their chief value will probably lie in preventing a given attack from 

 continuing by secondary infection during the succeeding seasons. A pond 

 which is water tight should be capable of holding fish again, even after its 

 fish have all died of infectious disease, with as little chance of a repetition 

 of the loss as existed before any disease occurred in it. This requires, of 

 course, a rather careful and thorough application of a powerful germicide 

 and subsequent thorough flushing to completely remove the substance 

 used. A number of such substances are efficient disinfectants, but since a 

 considerable quantity must be used, cheapness is an important consideration. 

 Slaked lime or quick lime are not sufficiently effective and should not be 

 used. Chloride of lime is to be recommended. In its application or that of 

 any disinfectant, it is essential that the flow of waver be stopped or reduced 

 to a very small volume. The chloride of lime may then be scattered over 

 the bottom and enough water admitted to allow the bottom and sides to 

 be scrubbed and washed down thoroughly with the solution resulting. In a 



