848 



BUI.I.ETIN OF THE BUREAU OF FISHERIES. 



which had much more room — each a 5-foot trough. The following table is a 

 full exhibit of the lots in the experiment and the principal facts in their history : 



Experiments with Spratt's Foods in 1907. 



Lot no. 



1939K 



1939L 

 1939M 



1939N 



1939O 

 1939P 



1939K1 

 I939N^ 



I939Z> 



1939Z3 



How treated — Feeding 3 times daily in all cases. 



Liver to June 30; fibrine to October 19 



Liver to July 20; fibrine to October 19 



Liver to June 30; then fibrine and liver on alter- 

 nate days to October 19 



Liver to June 30; then aquarium cereal to Octo- 

 ber 19 



Liver to July 20: aquarium cereal to October 19.- 



Liver to June 30; aquarium cereal and liver on 

 alternate days to October 19 



Rescued from 1939K August i6, and from that 

 date fed on liver exclusively; kept in a 5-foot 

 trough 



Rescued from 1939N August 16, and from that 

 date fed on liver exclusively; kept in a 5-foot 

 trough 



Liver to end of July; then liver, hearts, and lights 

 to October 9 



Liver to end of July; then liver, hearts, and lights 

 to October 10 , 



Original 

 number 

 of fish. 



Taken out 

 alive in 

 August. 



Close of experiment. 



Oct. 

 Oct. 



Oct. 



Oct. 

 Oct. 



Oct. 19 



Oct. 19 



Oct. 19 



Oct. 9 



Oct. 10 



Fish 

 left. 



466 



4 

 37 



48 



826 

 768 



Average 

 weight. 



Grains. 

 24. t 

 21. 7 



87.3 



29 3 

 23- 6 



158. S 



154 9 

 72. 6 

 82.6 



Before the end of the first month there developed an abnormal mortality 

 in the lot of trout fed on Spratt's fibrine, the dead picked out on the last seven 

 mornings of the month being as follows: 4, 2, 8, 11, 14, 21, and 34; total, 94; 

 as contrasted with the following deaths in the two large control lots," namely: 

 2, o, I, I, 2, and i; total, 7; the rate of mortality being thus, for those seven 

 days, forty-eight times as heavy with the fish eating fibrine as with those 

 eating liver. The heavy mortality in this lot continued till August 16, by which 

 time 480 of the 500 had been picked out dead, the losses in two control lots to 

 that date being only 29 in the aggregate, out of an original 2,000. 



The lot receiving liver till July 20 and fibrine for the rest of the season did 

 not develop any excessive mortality until September, but during that month 

 434 out of the 500 died. 



The lot fed on aquarium cereal suffered less, but they too had lost nearly 

 four-fifths of their numbers before the end of August, in the lot taking up this 

 food June 30, and in September an equally heavy loss befell the lot that began 

 this food July 20. 



On the 1 6th of August, as a sort of experimental rescue or secondary control, 

 there were taken out of the first fibrine lot of fish (1939K) 15 of the survivors, 

 and from the first aquarium cereal lot (1939N) 100 of the survivors. These two 

 rescue lots were henceforth fed on liver. The object was to see whether they 

 could, by a return to normal food, be rescued from the mortality that was fast 



. "These two control lots embraced in all four times as many fish as the fibrine-fed lot with which 

 they are compared. The rate of mortality in these control lots was 3^^ per thousand, while in the 

 fibrine-fed lot it was 168 per thousand. 



