74 American Fisheries Society 



to destroy fishes? Fishes usually turn about and swim 

 away when they encounter detrimental conditions oc- 

 curring normally in fish waters, — Do they avoid strange 

 poisons when they encounter them? 



The relative toxicity of thirty-four compounds result- 

 ing from the destructive distillation of coal and chosen 

 to represent natural groups, has been determined. The 

 small Illinois sunfish (Lepomis humilis) weighing 4-5 

 grams was used as a standard fish and the concentrations 

 used for comparison were those killing the standard fish 

 in one hour. The following list gives the results for 

 some of the groups of compounds in parts per million. 



Parts per million by weight 

 Compound to kill the standard fish in 



one hour. 

 Amonia 7-8 



Ammonia Salts 150-700 



Aniline 1000-1200 



Quinoline 52-56 



Sulphuretted Compounds 5-125 



Phenols and Cresols 50-90 



Heavy hydrocarbons 2-65 



Carbon monoxide (by Wells) 8 



All but three of the compounds studied were found to 

 be serious poisons. The condensed table above indicates 

 that the removal of any class of compounds would not ren- 

 der the residue harmless. 



In general the younger fishes down to 1.5 grams (sun- 

 fishes) are more sensitive than the larger ones. This is 

 true for the majority of compounds but a few, as carbon 

 bisulfide, are marked exceptions. Sollmann, using stand- 

 ing water, found that eggs of Funduli appeared less sus- 

 ceptible to poisons than either adults or embryos. His 

 methods were faulty, however, and it is probable that his 

 results were in part due to confining the fishes in small 

 quantities of water. Gortner and Banta found that cer- 

 tain phenolic compounds were about as toxic to amphib- 

 ian eggs as they are to the sunfishes used in this work 



