124 American Fisheries Society 



toxic in sea water. Copper sulphate was fatal within ten 

 hours at a concentration of four parts ; cadmium nitrate 

 within thirty-six hours at six parts, while nickle and co- 

 balt chloride were fatal within five days when as much 

 as sixteen parts were used, and manganese chloride in 

 six days at twelve parts per million. 



It is needless to say that in these experiments dupli- 

 cates have been run which closely agree, and that control 

 experiments have also been made to eliminate doubt as 

 to the effect of confinement in the jars in which the ex- 

 priments were performed. The controls showed that the 

 fish would live almost indefinitely under the conditions 

 to which they were subjected, provided that none of the 

 toxic salts were added. 



We see that many substances are toxic to salt-water 

 fish and many others to fresh- water fish. These contami- 

 nations may find their way into small streams and fish 

 ponds, also fish may be subjected to them during trans- 

 portation if the containers have these metals in their com- 

 position, for many kinds of waters have a great solvent 

 action upon them. Further work is being carried on 

 along these lines in which the effect of lime, coal-tar prod- 

 ucts, and factory wastes is being studied, and it is hoped 

 that sufficient work will be completed in the near future 

 to show the necessity of protecting our fish from these 

 pollutions, to which many are now subjected. 



