fall were 200 percent heavier than ilngerlings of the same hatch raised in trout ponds, 

 of a v/ater temperature of never more than 18 degrees, but for most of the tiine only 13 

 to Ut degrees centigrade. The losses in the carp ponds were 48 percent as against 

 losses of 80 to 90 percent in the trout ponds. 



Under intensive feeding conditions, water ten?)eratures of less than 20 degrees 

 centigrade are naturally recommended, since this makes for better hygienic conditions. 

 But aside from this, the optijual food assimilation, under similar temperatures, is 

 seemingly the same for brwm trout as for rainbow trout. Temperatures over 10 degrees 

 centigrade will provoke faster growth but not better food assimilation, i.e. do not lead 

 to economy in food. 



In trout ponds where the brown trout lives together with minnows. Wilier 's Thumb 

 (Cottus gobio ) and with groundlings, it is extraordinarily hypogynoua. Even when feeding, 

 it clings closely to the bottom, which distinguishes the brown trout immediately from the 

 rainbow trout. 



The brown trout is a winter spawner, spawns in currents and in pairs. From October 

 to Januaiy, but mostly in November and December, the brown trout goes up the brook. The 

 females, followed by a like number of males (Scheuring 1929/30) spawn their eggs in spots 

 of clear water of from 20 to 30 centimeters and in scooped hollows from 5 to 15 eentiaeters 

 deep. The pea-sized eggs are deposited into these holes. 



The flesh of brown trout and of all other trout varieties can be of salmon color j 

 their eggs can be full red if the food contains the red coloring matter (carotene), present 



in ganunarus and shrimp and in some mollusks. 



While brown trout, and similarly rainbow trout, possess relatively little capacity 

 for adaptation and domestication, they can nevertheless be raised profitably by means of 

 intensive culture. Numerous hatcheries have demonstrated that brown trout may be rsdaed 

 exclusively or in greater part through intensive artificial feeding. The excellent 

 showing made by some hatcheries in this respect are centainly the result of planned 

 culture. 



In one respect, the brown trout surpasses the rainbow trout, to wit: in its relatively 

 greater resistance to Gyrodactylus . On the other hand, brown trout is more apt to contract 

 furunculosis than rainbow trout. With regard to growth, brown trout, from my own observ- 

 ations and those of various trout fisheries, is not lacking behind the rainbow trout, under 

 like conditions, of course. 



3. The Rainbow Trout. 



The rainbow trout is a native of the California mountain regions. The fish was first 

 brought to Germany in 1880 through the German Fishbreeders Association, and through von 

 dem Borne. For the introduction of fresh blood these iu^jortations were repeated from time 

 to time, and 13 such importations were made between 1907 and 1926. 



Ehrenbaum has pointed out that the imported stock differed greatly in varieties. 

 Aside from the fixed-form dweller in mountain brooks ( Salmo Shasta, Jordan), different 

 crossbreeds and especially steelhead ( Salmo irideus . Gibbons ) came to Germany. 



The steelhead is supposed to have come by its name on account of the great resistance 

 of its head. This fish comes originally from the lower stream regions of these American 

 rivers which shed their waters into the Pacific Ocean, 



From here, the steelhead was distributed in the rivers of eastern North America. 

 Although the steelhead still spawns in cooler waters, it is nevertheless really a fish 

 of the mouths of great rivers, i.e. used to warmer waters. 



It is reasonable to assume that rainbow trout as well as steelhead retain these 

 characteristics in Germany. The introduction of the steelhead, at least, has fostered 

 the belief that rainbow trout is fundamentally not suited for planting in trout brooks. 



95 



