DEGENERATION OF AMERICAN TROUTS IN AUSTRIA. 987 



Latest example from the current year: Spring pond of 90 square meters, good 

 depth, and slow current of the water at a temperature of 10° C. ; there were in the 

 middle of February 400 beautiful rainbows from a lot of the previous year, of 

 which 950 had been taken out in apprehension of lack of water in winter and 

 sent to other places in November. The suspicious looking bluish tinge was 

 already awakening our anxiety; there was danger in delay, but the best remedy 

 was natural food. A broad flat pool with spring water flowing through it, all 

 covered with vegetation and alg£e, had become free of ice. Here were caught by 

 means of a fine dip net a mass of various small animal life, small and large larvae 

 of mosquitoes, crawfish, woodlice, small fishes, and even bullheads. The small 

 animal forms came slowly to the surface from the thick forest of vegetation and 

 dirt and were caught up. The entire mixture was then taken to the shallow 

 water near the bank of the pond, where the trout themselves took the food out 

 of this mixture. The pool supplied ample food year after year, thus saving the 

 fishes more than once, though diminishing in abundance each year toward the 

 month of May. Seven of these rainbows died, but all the remaining seemed 

 well and acquired within three months their normal aspect, which they kept. 

 To be sure, they were given no more food substitutes. The last 75 fishes were 

 sent away in July; they weighed each 13 kilograms and stood very well the 

 transportation of 6>^ hours, as did also those which were sent away earher. 



As long as the materials for the diet of the small fry and young fishes con- 

 tained crustaceans and fresh fish, the breeding and rearing went on exceedingly 

 well, but in winter, with the forced use of substitutes, or in proportion to the 

 lack of fresh fishes, the trouble began. 



3. Insufficient flow of water through the ponds. The two large ponds have 

 an old accumulation of ooze at the bottom some 20 to 100 centimeters deep; 

 can be emptied only down to five-sixths of their contents at best, as the entire 

 system of springs of the establishment flows through these. This, which it is im- 

 possible to correct, is surely an evil, but it had no apparent bad effect upon 

 the larger salmonoids and the breeding fishes so long as the flow was abundant. 

 When the supply grew less, in 1897-98, there appeared again the exophthalmia 

 and the "staggers" now and then. With the decrease of springs these phe- 

 nomena grew more frequent, several of the native trout (fario) became miser- 

 ably thin, and several rainbow trout yielded spawn that could not be used. In 

 1904 the establishment went through two or three months without the flow of 

 the springs, and in summer the surface water of the principal ponds at a certain 

 distance from the inflow of the water had a temperature of 18° and near the 

 exit a temperature of 21.2° C. At that time the water was calm, for what cur- 

 rent could be expected from a couple of second liters in an area of 1 3^ hectares ? 

 The water near the bottom was cooler by some 2° to 4°, and the trout lay there 



