Aincrican Fisheries Society. 35 



there, and the amount of vegetation in the lake is small, it may 

 do the work perfectly well. But if the conditions are as they are 

 in Lake Mendota, and it is a great deal worse in some other lakes 

 as reported by the Massachusetts Water Commissioners, you can 

 readily see you could not run a hatcheiy with that water. If the 

 bottom water is pure in late August and September, it would be 

 all right at any time of the year, but it would have to be a 

 matter of investigation with each individual lake. 



Chairman Wliitaker: There are some things that have oc- 

 curred to me in this connection, and I do not know but your last 

 remarks explain it. Do you know whether this condition of 

 affairs happens occasionally in a lake, or does it obtain in all 

 your lakes in a measure? 



Professor Birge: These temperature conditions belong to 

 all lakes of any depdi. 



Chairman Whitaker: I speak with reference to the foulness 

 of the water. 



Professor Birge: It depends upon the amount of the float- 

 ing plants and animals. There are various conditions in lakes 

 in that regard. In Green Lake, in Wisconsin, which, you may 

 know, is a lake of about the same size as Lake Mendota, though 

 of different shape, but al)out 200 feet deep, at a time when the 

 plankton vegetation is most abundant, there is not a fourth as 

 much as there is in winter in Lake Mendota. It is not a question 

 of bad water at all, but of the natural capacity of the lake to 

 grow vegetation. L^pon what that depends, I don't know, but 

 tliere is more difiference in lakes in capacity to grow vegetation 

 of different sorts, than there is between fields to grow grass, and 

 in lakes abounding with this vegetation the water will be foul. 



Dr. Parker: Did you learn anything about the presence of 

 female fish among those dead fish .■' 



Professor Birge: I made no observation on that, as far as I 

 recollect. 



Dr. Parker: How was it in regard to the bullheads, Mr. 

 Titcomb? 



Mr. Titcomb: The whole lake was cleared out of the dead 

 fish and we could not investigate it, as we did not learn of it in 

 time. I do not think there was anything abnormal in the 

 weather; I am sure they had spawned, as this was along in July 



