TREATMENT OF FISH-CULTURAL WATERS FOR REMOVAL OF ALG^. 887 



The first effect to be seen upon the algse when the concentration reaches the 

 toxic point is a shght fading of the natural color. When killed the algae filaments 

 become gray and shrivel markedly, occupying much less space than while alive. 

 The effectiveness of treatment is increased in warmer water. 



While trout are considered the most susceptible of the species used in fish 

 culture, there are probably some exceptions, at least under some conditions, as not 

 all species have been tested. Several white suckers at White Sulphur Springs 

 in one instance succumbed to a treatment which did not injure trout in the same 

 waters. Care must be always exercised in the matter of susceptibility. 



Great care should be exercised in the manipulation of the copper sulphate 

 salt, the copper sulphate solution, and in the calculations. The substance is not 

 a very deadly poison, yet it may have unpleasant effects upon the human system. 

 Ordinary handling of the salt or the solution will result in no trouble. The 

 siphon should not be started by mouth suction directly on the siphon arm, 

 however. A moderately strong solution taken into the mouth results in a very 

 disagreeable irritation of the mucous membrane and sometimes nausea. Attach 

 a small rubber tube to the siphon nozzle and fill the whole siphon tube by suction; 

 then pinch rubber tube to prevent back flow and detach it; the fiow will start. 



ILLUSTRATIVE AND SUGGESTED APPLICATIONS OF THE TREATMENT. 



AT BAYFIELD, WIS. 



The first experiment in the treating of water by this method on a consid- 

 erable scale was made at the Bayfield station of the board of fish commissioners 

 of the State of Wisconsin. A flow of 1,127 gallons of water per minute was 

 treated continuously for 47 days with copper sulphate so that a dilution was 

 maintained varying from i : 1,250,000 to i . 1,700,000. The dilution was varied 

 at will from time to time for various reasons. Upward of 15,000 brook, brown, 

 and rainbow trout from 2 to 3 years of age were held in this water, and during 

 the treatment no injury was done to any of them. The immediate result of the 

 treatment was the cessation of trouble with algse in the ponds affected by the 

 flow, a trouble consisting chiefly in the necessity of frequent cleaning of the 

 screens at the outlets of the ponds. The treatment ceased on July i. There- 

 after during the summer the algae sprang up again, and much attention was 

 necessary to the screens to keep them free of the clogging strands of the fila- 

 mentous species common in these waters. 



This effect upon the algse was not the purpose sought in this experiment at 

 the Wisconsin station, but was incidental thereto. For several weeks of each 

 summer the brook and other trout at this station are attacked by bacterial 

 infection, the specific cause of which has been described under the name Bacte- 

 rium truitce. The ravages of this parasite are worst while the temperature ranges 



