896 BULLETIN OF THE BUREAU OF FISHERIES. 



Various industrial wastes are of course injurious in sufficient concentrations, 

 but the actual effect of some of these has been exaggerated, perhaps partly 

 because they are sometimes highly colored and of unsavory appearance. Paper- 

 pulp mills which use the sulphite process spend a dark-brown liquor of strongly 

 acid reaction which contains, besides the chemicals used for extraction, the 

 extractive matters themselves, organic compounds of comparatively complex 

 nature. These latter are themselves often toxic to fishes, as well as the extract- 

 ing agent, and the effluent containing both is presumably always quickly 

 destructive to fish life in its undiluted condition. When discharged into streams 

 it quickly undergoes great dilution, and it becomes of interest to know at what 

 point it is rendered harmless. A sample from Covington, W. Va., at a dilution 

 of I to 200 did not injure salmon fry during 2 days. It is evident that tremen- 

 dous amounts would be required to raise the water of a stream of any size to a 

 fatal concentration. It has been suggested that when wastes containing sul- 

 phites kill fishes the loss of dissolved oxygen due to the reducing power of 

 the sulphite contributes to the result by tending to asphyxiation. A sample 

 experimented with by the writer had little or no reducing action on the dis- 

 solved oxygen in the water, and it is likely that it kills by its direct action alone. 



Other industrial pollutions, such as the wastes of paper-pulp mills using 

 the soda process, tannery wastes, and dye wastes from knitting mills, will kill 

 fishes, but the most toxic of them are made harmless to such fishes as black 

 bass and yellow perch by the addition of a few hundred parts of water, usually 

 200 parts. Wastes from the manufacture of illuminating gas, however, require 

 some hundreds of thousands parts of water to dilute them to harmlessness. 

 The water soluble substances in bark and in the wood of some trees are capable 

 of killing fishes, but while such products are undesirable in streams the amounts 

 of bark and wood necessary to affect fish in flowing streams are so large that it 

 is not likely that they do much direct damage to fishes by the substances which 

 dissolve from them. 



Tobacco ashes have been said to kill trout fry in transportation cans. 

 After trials with salmon fry no effect whatever could be detected unless the fry 

 were in the sac stage and lying on the bottom with the free ash, when they 

 would suffocate from clogging of the gills. If the ash was wrapped in a cloth 

 or if the fry were free swimming there was no effect. It is possible that the 

 ash from other samples of tobacco would give a different result. 



Fishes are very susceptible to acid water and succumb to the mineral acids 

 in very weak solutions which scarcely taste sour. Hydrochloric acid kills mum- 

 michogs and sunfish when enough has been added to destroy the alkalinity and 

 make about 8 parts of acid per million. Some 40 hours were required for the 

 sunfish. The mummichog or bull minnow is more susceptible than the sunfish. 



