128 American Fisheries Society. 



studying one great source of food for fish in small lakes and therefore 

 under conditions that are so limited in space as to permit such a study, we 

 have done this in the hope of establishing principles and securing knowledge 

 which will help all fisheries in the end. 



Mr. Titcomb: Conceding that most of the little fishes keep away from 

 the deeper water, it would appear that the main usefulness of these plankton 

 organisms is at the bottom? 



Dr. Birge : If there is no appreciable number of small fish that are 

 utilizing this material, then its main usefulness must be at the bottom. But 

 I am not prepared to say that this is the case until the subject has been 

 studied much more accurately than has hitherto been done. Our studies 

 have been chiefly on the deeper water, but most of the fishes that this 

 Society is directly concerned with are shore fishes, or shallow water species. 

 Other forms of food may be more important to some of them than this 

 plankton. Of course, the whitefish and lake trout, all the whitefish group, 

 are open water fish. Has anyone ever tried to breed the young of the 

 gizzard shad, Dorosoma ccpedianum, as a food minnow? This fish, as you 

 know, feeds on plankton algae, and if it will multiply freely in lakes it 

 might become a valuable foodfish, especially as it lives on material which 

 very few fish can utilize. It seems to be more abundant in streams but is 

 not absent from lakes. 



Dr. Emmei-ine Moore, Albany, N. Y. : In the early part of his re- 

 marks Dr. Birge referred to the source of the fishy odor as being mainly 

 due to the crustaceans — Daphnias, Cyclops, and so on. Do you find that 

 such flagellates as Synura and the Peridinese, when they develop in very 

 great numbers, are quite as much a source of that trouble? 



Dr. Birge : We have never found Synura in large numbers. It has 

 been the same with Peridinese — we find a few, but not enough to make 

 any considerable part of the weight of the food. I should not doubt that 

 these Crustacea may get this fishy material out of oils in the vegetable food. 

 I think that it is certain that they concentrate it; I will not say they 

 manufacture it, though they may do this also. I was talking about the 

 way the fish flavor got into the fish, and I think it does get in very largely 

 through these Crustacea, at least for fish that eat Crustacea freely. I think 

 they are feeding on these very fishy oils, and that that has something to 

 do with their flavor. 



Mr. W. E. Barber, LaCrosse, Wis. : In your research, Dr. Birge, have 

 you determined why the perch in Lake Mendota run so small — why there 

 are no large perch? 



Dr. Birge : No, I have not determined that, but if you want a guess I 

 will give you one. In 18S3 or 1884 there was an enormous mortality of the 

 perch in Lake Mendota. They died by the million and their bodies were 

 washed up along the shores ; for years there was a windrow of bones all 

 around the lake. Now, I can give you no statistics, but those perch that 

 died were decidedly bigger than the perch that are now there. My theory 

 has been this : the epidemic did not hit the little perch, and the death of 

 the larger fish, which prey on the little ones gave these little fellows a fine 



