Hayford. — Plant Life in Trout Ponds 87 



In February of the present year, the President of our Depart- 

 ment gave me permission to engage Mr. Wm. T. Foster, Professor 

 of Biology in Lafayette College, to give scientific assistance in 

 carrying on experiments. Wednesday and Saturday of each 

 week were devoted to this work which extended to July first. 

 Special attention was given to the more important diseases 

 affecting brook, brown and rainbow trout. 



In view of the fact that this disease was confined to certain 

 pools, Professor Foster, by microscopic examination, was soon 

 able to discover the disease organisms in those fish showing 

 pathologic symptoms, for the purpose of discovering some means 

 of preventing the disease or effecting a cure as the disease appeared. 

 These examinations began in February and are still being carried 

 on. Hundreds of brook, brown and rainbow trout were examined 

 to ascertain the cause of the disease conditions which appeared 

 from time to time. 



There were two very important diseases with which we came 

 in contact. One was a blood disease, caused by the microscopic 

 organism known as Bacterium truttce, and the other by a protozan 

 known as Ichthyophthirius multifillis. (A translation of pp. 

 122-128 of Hofer's Fischkrankeiten, Munchen, 1904, was furnished 

 by the U. S. Bureau of Fisheries). The prescribed measures were 

 employed and proved efficacious. 



In the case of the first named disease the fish could be readily 

 picked out and every fish exhibiting typical pathological con- 

 ditions showed the presence of the organisms in large numbers 

 in the heart's blood. The morphological characteristics of these 

 organisms have been fully described by Mr. M. C. Marsh, formerly 

 of the U. S. Bureau of Fisheries, but so far as we have been able 

 to ascertain, no direct preventive or curative measures have been 

 discovered up to this time. We have not carried on our investiga- 

 tions far enough to entirely eliminate the organisms, but we have 

 succeeded in eliminating the disease this year in some of our 

 ponds and in reducing the mortality in others more than 90% 

 by employing the following methods: 



Introduction of Potamogeton crispus, Elodea and water-cress in 

 clusters, to the extent of about ten per cent of the pond area in 

 ponds of spring water at 52 to 62 degrees. In ponds 50 feet long and 

 7 feet wide with a depth of water of 2 to 2 3^ feet, it is necessary 



