482 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
THE FISH EPIDEMIC IN LAKE MENDOTA IN 1884. 
Early in July, 1884, public attention was attracted, at Madison, Wisconsin, to the 
extraordinary numbers of fishes dying and floating ashore in Fourth Lake or Lake 
Mendota. By the middle of the month the accumulation of their rotting bodies along 
shore had become a public nuisance, and the street commissioner began to cart them 
away from the city front and bury them. By the 19th not less than 15 tons had been 
thus removed, and by August 4 from 75 to 100 tons. As the city borders only a 
small part of the lake, it was estimated that fully 300 tons had died up to that time. 
On August 7, the Madison Transcript reported that 200 tons had been hauled away 
by the city authorities during the four weeks preceding, and that the fishes were still 
dying. August 15, when the writer arrived at the lake, this remarkable epidemic had 
practically ceased, and during the week following (about six or seven weeks after its 
beginning) it disappeared completely, not to return that season or the following 
summer. 
By far the greater part (perhaps 90 per cent.) of the fishes which perished were the 
common perch {Perea flavescens), much the most abundant species in the lake. Next 
came the lake herring {Coregonus artedi),* locally called the “white fish;” while 
pike-perch, white bass, and sunfish (Lepomis) were much less numerously represented. 
My own first visit to the lake was made in consequence of a request from Professor 
Baird, then U. S. Fish Commissioner, conveyed in the following letter received by me 
at Normal, Illinois, August 13 : 
Wood’s Hold, Massachusetts, August 10, 1884. 
Dear Sir; Would it be convenient for you to visit the districts in Wisconsin where the mortality 
among the fish has developed itself to a very great degree ? If you can, I will be glad to have you 
make a thorough investigation of the circumstances of the case. * » » j consider it a matter of 
very great importance, and one that should occupy the careful attention of specialists. I requested 
specimens to be sent to Mr. Kyder for his examination, but an investigation in the field on the sick and 
dying fish will be of much more importance. 
Yours truly, 
Spencer F. Baird. 
I arrived at Madison August 15 at 2.30 p. m., with seine, dredge, microscope, and a 
suitable apparatus for studying the fresh fluids and tissues of the diseased fishes, and 
for the permanent preservation of material of all kinds likely to throw any light on 
the subject under investigation. Through the kind assistance of Hon. Philo Dunning, 
of Madison, president of the Wisconsin State Fish Commission, a work-room was 
obtained at once in the boat-house of the steamer company, at the principal landing, 
and I spent two hours on the lake the same afternoon in search of dead and dying 
fish. I remained here until August 22, making collections as opportunity offered, 
carefully examining the freshest obtainable specimens for evidence of fungous parasit- 
ism, making numerous autopsies of fishes recently dead, preparing and staining slides 
of the blood and other fluids of those not yet dead when taken, for bacteriological 
study, and preserving the tissues of such fishes for later histological work. I also 
dredged the lake along shore and in deep water, as described in a foregoing part of 
this paper, but lack of time prevented my making as extensive general collections as 
was to be desired. 
* This fisb was introduced from Lake Michigan some years before, according to information given 
me by Mr. Philo Dunning and others. 
