24 American Fishe?ies Society 



streams where the introduction of lime would be more 

 far-reaching in its effect than copper sulphate. 



To avoid the necessity of having each boatman return 

 to the source of supply one boat should be detailed to 

 carry a supply of sacks filled and ready to replace the 

 empty ones at any place on the lake where needed. This 

 is important. 



Some of the copper sulphate will not dissolve readily 

 and the supply boat will find a few pounds remaining in 

 each sack when he makes the exchange. This can be 

 gathered from the various nearly empty sacks into one 

 and this may be dragged over the surface until dissolved. 

 To deposit a bag of the material at any one place will 

 have very little effect. It must be dissolved at the sur- 

 face of the water in ponds of ordinary depths. There 

 is too little knowledge of the subject to attempt to advise 

 how to exterminate fish in very deep lakes. 



DISCUSSION. 



Prof. Dyche, of Kansas: There are unquestionably tremendous op- 

 portunities for improving the productiveness of waters by getting rid 

 of surplus fishes and introducing finer species. However, you cannot 

 attempt to destroy a species of fish in a pond for the introduction 

 of others unless you destroy all of them. If more than a single indi- 

 vidual of the former species is left it will be only a question of time 

 till conditions are back where they were before. Unless the destruction 

 is complete the introduction of finer species must fail. 



Mr. Graham, of Massachusetts: In New England and New York 

 there are numerous ponds that formerly contained trout and salmon, 

 which today contain only bass, perch, pickerel and such species. There 

 is a great demand for the planting of trout and salmon in these ponds, 

 but is almost impossible to establish them in the presence of the other 

 fish. This work of Mr. Titcomb's is very important in showing how 

 we may be rid of the pernicious fishes. At the suggestion of Mr. 

 Titcomb I tried out this method on a pond belonging to a friend. The 

 pond was full of pickerel. We first drained it down till there Was 

 only the stream running through, and then put in the copper sulphate 

 at the spring which feeds the pond. We kept this up for a week, and 

 at the end of that time it was impossible to find any living thing in 

 that stream except the bullheads — they seemed to thrive on it. 



In a little pond in my back yard, about 12 by 30 by 2Yz feet deep, 

 in which I have a number of kinds of fish, I desired to get rid of the 

 algae. I used about a half pound of copper sulphate in a sprinkling 

 can of water and distributed it about over the surface. It was very 

 effective on the algae, which died and sank to the bottom, but there 

 was a secondary effect produced by the decomposition of the algae in 

 which there was a large amount of carbon dioxide liberated. The im- 

 mediate effect of this was that the fishes came to the surface gasping 



