Titcomb. — Destruction of Obnoxious Fishes 25 



for air. The suckers came first, then the black bass, and later both 

 died. The perch and sunfish withstood it perfectly, but a number of 

 minnows were lost. The bullheads all came to the surface, but none 

 of them died. 



Mr. Titcomb: We must learn in all cases what proportions to use. 

 In one town we have ten trout ponds which, I believe, could be rid 

 of the yellow perch and pike-perch successfully, at a cost of perhaps 

 $400 to $500, and so restore them as trout ponds, together with the 

 streams tributary to them. 



Mr. Bower, of Michigan: We have in Michigan thousands of lakes 

 containing undesirable fishes and we would be very glad to find some 

 method of destroying all the desirable as well as the undesirable fishes 

 in order to start in with a clean sweep, using only the best and most 

 desirable species. I wish to inquire whether there is any method of 

 reaching fishes in deep lakes, say down to 100 feet? Also I wish to 

 inquire whether it is feasible to destroy the carp, which bury them- 

 selves in the mud? Perhaps the bullheads escape by burying themselves 

 in the mud, and so escape the toxic effects of the copper sulphate. 



Mr. Titcomb: In Dr. Kalbfuss's experiments he found that the carp 

 was one of the first to succumb. I think it is even more sensitive than 

 the trout and one can get rid of the trout without destroying the other 

 fishes by making the solution only one part in six millions. That is 

 getting it down to very small proportions and it is not easy to figure 

 the cubic contents of a lake. As to deeper waters, I think it is pos- 

 sible in any depth of water; but I have not tried it at a depth greater 

 than 25 feet. 



A Member: How does this affect the fish? If they are stunned or 

 killed outright are they rendered unfit for food? 



Mr. Titcomb: They die slowly and come to the surface. They do 

 not keep well after they are killed by this method, and I do not think 

 any one would care to eat them. 



Mr. Marsh, of New York: I believe Mr. Bower could use copper 

 sulphate in lakes of any depth. It is merely necessary to sink the 

 bag to the depth you wish to reach and let the crystals dissolve there 

 where they will come into contact with the fishes you wish to kill. 



Mr. Cobb, of Minnesota: We had an experience with copper sul- 

 phate, but it is not as valuable as it might be, for we do not know 

 just what took place. In a small lake used for bathing purposes all 

 the fish were reported dying. I went out to it and found that all the 

 animal and vegetable life of the pond was dead or dying and discov- 

 ered a substance on the shore that proved to be copper sulphate. The 

 work was evidently done in the evening by persons having access to 

 boats. One thing which interested me was that horses were drinking 

 from the lake the next morning and campers were getting their drink- 

 ing water there, and it had apparently no effect on any of them. 



Mr. Titcomb: That brings out very clearly the fact that the copper 



sulphate precipitates very rapidly. You can poison a lake very effec- 

 tively and feel perfectly sure that you have not destroyed the fishes 

 in a stream below. 



A Member: How soon afterwards can a lake be restocked? If it 

 can be done soon it would be possible to clean out some of the desir- 

 able fish and hold them for restocking the pond after the others have 

 been exterminated. 



Mr. Titcomb: That is quite feasible. After three or four days the 

 fish could be put back safely. 



A Member: If the fish were good to eat after being killed in this 

 way it might be a very dangerous thing in the hands of certain people 

 who make a practice of getting fish in any way they can. If they 



