14 REPORT OF THE COMMISSIONER OF FISHERIES. 



FISH DISEASES, WATER POLLUTIONS, ETC. 



A number of investigations have been conducted b^^ the Bureau to 

 determine causes and remedies for epidemics and unfavorable condi- 

 tions affecting both wild and domesticated fishes. This phase of the 

 Bureau's work is regarded with much confidence b}" those in charge of 

 State and private hatcheries, and advice and recommendations have 

 been furnished in answer to numerous requests. 



An important case was a heavy mortalit}' among brook-trout ivy at the 

 State fish hatchery at Roxbury, Vt., where 1,200,000 out of 1,300,000 

 fry had died before the full absorption of the yolk sac. A fluctuating 

 gaseous content of the water was found to be the cause of the trouble, 

 Which can be removed onl}" by artificial correction of the water supply. 

 At Bayfield, Wis., the death of many trout in the ponds of the State 

 hatchery was found to be due to a bacterium which is peculiar to that 

 species of fish and which has caused widespread destruction at a num- 

 ber of hatcheries. Experiments are being conducted to determine a 

 means of destroying this organism, which was first discovered and 

 isolated some four j^ears ago by the pathologist of this Bureau. 



Considerable work has been done during the year to determine 

 the effects upon fishes of certain industrial wastes commonly discharged 

 into streams in the Potomac drainage basin. The principal species 

 experimented with were large-mouth black bass and j-ellow perch, 

 typical fishes of the Potomac system. To support fish life the water 

 must have a slightly alkalin-e reaction and in dealing with acid pollu- 

 tions the results of the experiments are affected by the alkalinity of 

 the water used as a diluent. In the present experiments the latter 

 was in all cases Potomac service water, tested for alkalinity at fre- 

 quent intervals. The degree of aeration also affects the results. City 

 sewage and wastes of various kinds from paper and pulp mills, tan- 

 neries, and gas works were experimented with under various condi- 

 tions of dilution and aeration. The gas-works wastes were generally 

 fatal in extreme dilution, while most of the other materials lost their 

 toxic qualities when mixed with greater or less quantities of Potomac 

 water, especiall}' when thoroughly aerated. The results of this work 

 will have an important bearing upon legislative and other projects for 

 the improvement of streams. The report will be published b}^ the 

 United States Geological Survey as part of a water-supply and irriga- 

 tion paper entitled "The Potomac River Basin." 



The west branch of the Penobscot River, in Maine, was examined 

 for pollution from a pulp mill at Millinocket. Chemical tests revealed 

 no contamination at that time, but the heavy coating of paper-mill 

 refuse on rocks and other objects along shore which had been under 

 water showed that the water has at times been seriously polluted. 



