22 American Fisheries Society 



lakes must we look more and more for our supply of na- 

 tive food and game fishes. 



The copper sulphate precipitates so rapidly that there 

 is little danger of contaminating streams flowing out of 

 lakes while the poison is being administered. 



As a result of the experiment at Silver Lake, the Lake 

 Tarleton Club in New Hampshire has undertaken the 

 extermination of pickerel in a forty acre trout pond with 

 a view of restoring it to its primeval conditions. 



Laboratory tests indicate that twelve pounds of copper 

 sulphate evenly distributed to one million gallons of wa- 

 ter will cause the death of such common fishes as pike- 

 perch, yellow perch, and pickerel (Esox reticulatus) . 

 These are the species most commonly found in the trout 

 ponds of New England, but many such waters are ruined 

 for trout by the presence of black bass. 



If the water contains an abnormal amount of lime a 

 larger proportion of copper sulphate must be used. As 

 it is impossible to know all of the subaqueous conditions, 

 variations of depth, spring holes in the bottom of the 

 ponds, etc., twenty to thirty pounds of copper sulphate 

 per million gallons is a safer solution to use, as the suc- 

 cess of the work depends upon the extermination of every 

 pair of fish of the species it is desired to kill. With pres- 

 ent knowledge it is impossible to tell what solution is 

 necessary to exterminate black bass, but it must be much 

 stronger than the one above referred to. No laboratory 

 tests have been made with the pike, pickerel (Esox lu- 

 cius), but from the results at Silver Lake where thirty 

 pounds of copper sulphate were used to 100 million gal- 

 lons, it is evident that this species is in the class with the 

 black bass. There is no definite information as to the 

 resistant qualities of the rock bass which also infests 

 many waters in the northern states which were once 

 trout waters and which, but for the presence of some of 

 these fishes, would still be trout waters. 



To persons undertaking to destroy fish in a pond or 

 lake the following suggestions are offered : 



First ascertain the volume of water. This, of course, 



