waste entering Maumee River contained 30 parts per million, or about 



one half of the amount necessary to kill the sunfish in one hour. 



Dilution by river water would lower the concentration rapidly. 



However, it is unsafe to conclude that the waste could not kill 



fishes, for Shelford (page U03) found that several species reacted 



positively to concentrations which would kill them in two or three 



hours. It seems unlikely that large numbers would be killed in 



Maumee River, although many might be affected adversely. Van Oosten (1929) 



reported that, in Saginaw Bay, the growth rate and quality of flesh of 



fishes were affected by dichlorobenzol released in Saginaw River, hO miles 



above the mouth. 



While there are almost infinite possibilities of fishes being 

 harmed by trade wastes in Maumee and Raisin Rivers, it is by no means 

 certain that they have been harmed to any great extent. The facts that 

 Professor Reighard reported numerous fish in lower River Raisin, and 

 that fishermen set their nets just outside the mouth of Maumee River, 

 shows that poisons are not regularly present in lethal concentrations. 



Another point of considerable importance in this connection is 

 that there was a -direct relationship between the abundance of plankton, 

 both plant and animal, and the intensity of pollution as indicated by 

 the chemical determinations. It is reasonable to suppose that concen- 

 trations of chemicals which would be harmful to fishes would also be harmful 

 to plankton organisms. For that reason it is difficult to believe that 

 the very large numbers of algae and Crustacea found in Maumee Bay in 1930, 

 could have existed in the presence of trade wastes of sufficient concen- 

 tration to be of great harm to fitches. 



It must be evident from the foregoing discussion that the 

 available data prove nothing with regard Lo the effect of chemical pol- 

 lution on the fishery. However, the presence of water low in oxygen and 

 high in free carbon dioxide, even in restricted areas, hardly can be 

 regarded as a desirable condition. The presence of poisonous trade 

 wastes is even less desirable. In the opinion of the writer chemical 

 pollution probably has been harmful to the fishery, but it seems equally 

 probable that it has not been the primary factor in depletion. The 

 possible advantage to the fishery resulting from the addition of large 

 quantities of soluble nutritive materials iri.ll be considered in a later 

 section. 



Bacterial pollution 



In 1929, this investigation included a study of bacterial pol- 

 lution in Western Lake Erie and its tributaries by Dr. .;illiam C. Beaver. 



30i4 



