Stream Pollution" 33 



Toxicity of Gas House Wastes 



Marsh (1907) showed that tar is extremely poisonous to perch 

 and bass. Illuminating gas is also very toxic. How small the amount 

 actually is has been determined experimentally by Shelford (1917: 

 391) who states that " it may safely be said that ten to twenty parts 

 per million of this waste [from a city gas plant] killed a 4-5 gram 

 Lepomis humilis [the small sunfish] in an hour." Wells (1918, 

 p. 568) , in summarizing his experiments on the two gases, says that 

 both CO and C0 2 are poisonous to fishes, though the former is very 

 much more deadly. So far as C0 2 is concerned, fishes are verv 

 sensitive to small changes in the amount of it in the water and seek 

 to avoid harmful concentrations by turning away from them. Fishes 

 do not, however, appear to detect CO in the water and enter con- 

 centrations of it that kill them in a few minutes. These concentra- 

 tions are such as would follow the introduction of gas house wastes 

 into water bodies. At the close of an extended series of experi- 

 ments in the reactions of fishes to wastes, Shelford (1917:392) 

 writes that " much of the danger to fishes from pollution of streams, 

 especially when the pollution is local, is determined by the reactions 

 of the fishes to the polluting substances. Fishes turn away from 

 dangerous substances which are normally found in -their usual 

 environment, but with strange or unusual substances, such as are 

 thrown into streams by gas-works and other industrial plants, they 

 frequently enter and follow up to points where the concentrations 

 are fatal, or fail to recognize the dangerous substance at all and 

 often stay in it until they are intoxicated and finally die there." 

 In support of this conclusion he shows the results of experiments 

 in a series of charts and graphs. Fishes are positive* in their 

 reaction to gashouse wastes in all concentrations which Shelford 

 used in his experiments. The complexity of the quest" ons involved 

 is also shown by the statements of Wells, who determined that fishes 

 vary much in power of resistance to different substances with the 

 season. From the middle of June to the end of July resistance is 

 least, and such fishes as the cyprinids die almost as soon as they are 

 taken from the water. The resistance rises slowly from this time 

 to September and then more rapidly until at the maximum in March 

 and April all fish are very resistant. As the breeding season comes 



*An animal is said io react positively to a stimulus when it moves towards 

 the source of the stimulus and negatively when it moves away from the 

 source. The positive stimulus attracts the animal whereas the negative 

 stimulus repels it 

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