888 BULLETIN OK THE BUREAU OF FISHERIES. 



between 50° and 60° F. Copper sulphate even in weak dilution inhibits its 

 action. It was therefore thought that by impregnating the water continuously 

 with this salt, at a dilution harmless to the trout, during the few weeks while 

 the disease usually prevailed, the loss caused by it could be prevented. 

 On account of a break in a conduit and the loss of a large number of the experi- 

 mental fish from certain ponds, the results of this trial were inconclusive. 

 The total losses in the ponds affected, as compared with those in control 

 ponds, so far as they are of any significance indicate a considerable inhibi- 

 tion of the disease among the brown trout, but the demonstration is not suffi- 

 cient to set up a claim of practical prevention of the disease in question. The 

 value of this application is for the future to determine. But the particular 

 experiment cited is held to demonstrate the feasibility of long-continued treat- 

 ment of large volumes of flowing water containing trout with dilutions of copper 

 sulphate of sufficient strength to have an inhibitive effect upon bacterial para- 

 sites of fishes and to be at the same time harmless to trout. The expense more- 

 over is well within the means of fish cultural operations. In the case cited it 

 was less than $1 per day. The volume of water treated was unusually large, 

 being more than i ,000 gallons per minute. 



AT WHITE SULPHUR SPRINGS, W. VA. 



At the United States fisheries station at White Sulphur Springs, W. Va., 

 copper sulphate was applied to the water supply of ponds containing trout for 

 the specific purpose of eliminating troublesome algae. A floating siphon appa- 

 ratus was used, similar to that already described, but on a much smaller scale. 

 By 24-hour trials of a few fry in fish cans with copper-sulphate solutions of dif- 

 ferent strength, the approximate strength which the species would endure for this 

 period and in the given water was ascertained to be about i part of sulphate 

 to 3,000,000 of water. The flow of water was estimated at 1,000 gallons per 

 minute. The siphon flow was adjusted so that the above strength was applied 

 to the whole flow. Within 24 hours a marked effect upon the algae was 

 visible, and a few trout in the raceway which conveyed the water to the ponds 

 were killed. None of the trout (both fingerling and adult brook and rainbow) in 

 the ponds were killed, but the sulphate was not without its effect upon them. 

 It was noticed that the fry either did not feed with their accustomed readiness 

 or refused food altogether. Like cattle and other domestic animals, they were 

 "off their feed." On this account the strength of the solution was readjusted 

 so that a i to 4,000,000 flow was maintained in the ponds. In the case of this 

 dilution there was still a noticeable effect upon the trout, as evidenced by 

 their refusal to take food. With young fish — fry and fingerlings — this effect 

 was seen after about 8 hours' application of the treatment. With adult 



