30 Tivciify-sixtli Annual Meeting 



very great mortality among the perch. There must have, on 

 a moderate estimate, from five to eight milHon of perch died in 

 the lake during the summer. You remember it very well, Gen. 

 Bryant? They washed up there on the shore. The street 

 superintendent buried from the city ])ank of Lake Mendota over 

 200 tons of these dead perch that washed up there, and that in- 

 cludes, perhaps, only three miles of the front of the lake, which 

 must be some twenty miles in circumference, and they were 

 washed up like that all around the edge of the lake. 



You will find a report of tliis by Professor Forbes, who 

 came up there to investigate the cause of the fish dying. He was 

 sent there by the Fish Commissioner, and came there in the 

 latter part of the mortality, and he found nothing 3s to the cause. 

 I studied it all through the season, but was unal^le to discover 

 any cause. 



Professor Forbes' report is found in the eighth volume of the 

 Bulletins of the U. S. Fish Conmiission. 1887. 



Chairman Whitaker: Were there any physical appearances 

 in the fish to indicate anything in the way of parasites? 



Professor Birge: You could see nothing; no, there was noth- 

 ing in the way of parasites. You would find fish swimming 

 around the surface. On a calm morning you could look out over 

 the lake and you could see the lake spotted with these fish as far 

 as the eye could reach; many of them dead, some of them feeble 

 and wriggling around the surface. If you picked up one of those 

 fish the blood from that slight pressure would simply strain out 

 over your hands, and on opening one, the intestines seemed to be 

 drained of blood, it was all choked in their gills. If you examined 

 them, you would find practically that all the blood of the body 

 was in the gills and kidney. Now, I saw nothing to account 

 for this. I studied the blood vessels and cut sections as well as 

 I knew how, and I was still unable to find anything. Professor 

 Forbes also worked at it and was unable to discover anything. 



Within the last two or three years, since finding this accumu- 

 lation of decomposing matter in the bottom water, it has occurred 

 as a possi])ility, but I would not give it as anything more than a 

 possibility, that there may be poisonous compounds in the water 

 which might be the cause of such epidemics. The stomachs of 

 the fish were nearly empty, though sometimes they had insect 

 larva in their stomachs, the regular food on which they lived, 

 and there was nothing to apparently cause this epidemic. 



