Mth regard to Trater temperature the same applies to rainbow trout as to brown 

 trout. I have experimented with thousands of trout fry and which I raised to fingeiv 

 llngs in carp ponds. The surface temperature of these ponds t;ou1q reach at times 30 

 degrees centigrade, still the losses (without artificial feeding) were only from 32 to 

 52 percent. 



In a large hatchery I found rainbow trout placed (for prophylactic reasons against 

 gyrodactilus) in small, shallow ponds without any through flow and under intensive feed- 

 ing conditions. The temperature would rise at times to 2L degrees centigrade (and even 

 more) and about 150 broodlings were counted per square meter. No ill effects irtiatsoever 

 were observable. 



It may well be said that rainbow trout are less "stenotypiciJ." than brown trout. 

 Their adaptation latitude and power is even greater, but as to oocygen requirements rain- 

 bcw trout are on a par with brown trout. 



Notwithstanding these findings, I am — together with Buschkiel— of the opinion that 

 the water temperature for rainbow trout should be kept at from 5 to 15 degrees centigrade, 

 that is, under conditions of intensive culture and for the same reasons as in the case of 

 brown trout. This applies especially for the intensive breeding of adult fish. 



If the most rapid growth is desired, the upper point of this temperature range 

 should be maintained since the temperature reacts strongly upon the growth of trout. 

 Carefully conducted experiments by Cornelius have shown that the rate of highest food 

 absorption occurs at temperatures of 19 degrees centigrade. 



Best food assimilation and lowest food quotient have been noted (in the case of rain- 

 bow trout) at a water temperature of 9 degrees centigrade. 



Feeding with fish, at a temperature of lo degrees centigrade showed a food quotient 

 of 2,9, and of 6 at a temperature of 17 degrees. 



The ratio between anabolism and metabolism is therefore best at a temperature of 9 

 degrees while a temperature of 10 degrees assures best food assimilation. Of course, 

 feeding under lower temperatures requires greatly prolonged work since the fish grow 

 slower under temperatures of 9 degrees than under temperatures of from 15 to 20 degrees. 



The great preferences for rainbow trout (over all other varieties) under intensive 

 culture conditions and -ttiich have made rainbow trout THE fish In trout fisheries are 

 based uponi 



(1) Its adaptation capacity to environmental changes (with especial regard 

 to intensive feeding) and domestication in general. 



(2) Its resistance against certain diseases, furunculosis, for instance, 



(3) The possibility of speedier hatching at higher temperatures in the 

 spring, hatching after typical winter spawners and shorter terms of 

 incubation. 



As disadvantages we list its susceptibility to Gyrodactilus, straying from natural 

 habitats and the alleged lower quality of its meat . 



In my opinion, the latter is not at all proven as compared with brown trout and 

 char. Quite often this is merely prejudice, since fish under artificial feeding con- 

 ditions (rainbow trout are mostly fed thus) do not taste as good as natural feeders. 

 This inferior taste disappears gradually, though quite slowly by keeping the fish in 

 clean water. 



I have made an experiment along these lines: I served trout to unprejudiced persons 

 (some of the fish were naturally fed, others had been artificially fed with a mixture of 

 fish meal, meat meal, spleen and shrimp). When served right after drainage of the ponds. 



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