During the first year, the perch-pike feeds exclusively upon plankton; its rearing 

 in caobinaticr with carp and tench is therefore clear profit. The perch-pike prefers 

 by nature turbid waters, rich in plankton and of a hard bottom. It thrives well in only 

 feebly eutrophic ponds. 



The Trout 



Trout as a side line is significant only in smaller carp ponds, and the rainbow trout, 

 of all species is best stilted. But, even rainbow trout requires not too muddy ponds, due 

 to its great demand for oxygen, in order to avoid considerable losses by fishing them out. 

 The fishing-rout.must be done with a "fishing box" or a seine. 



The trout breeder can raise his spawners to advantage in caip ponds. Rearing ponds 

 for carp are occasionally also used for the rearing of trout fingerlings. Good results 

 will only be. had, when the carp are already big enough so that the trout will not catch 

 up with them, since they would simply eat them up. 



Rairtoow trout are of no use for "policing" carp ponds. 



Other fish, like Tlhiting (dace) and eel are of no consequence as side lines, although 

 they are raised occasionally in nondrainable ponds, which are difficult to fish out. The 

 eel, at present, do certainly not belong in drainable ponds. 



Chapter V 



TROUT CULTURE 



A. Characteristics of the different varieties of trout 

 and environmental requirements for their culture , 



1. General 



Just as caiT^ fisheries raise tench and other fish as side lines, so do trout 

 fisheries. They also raise other fish but especially various trout "species" or rather 

 varieties. These different varieties are of different economical value and also differ 

 in habits and requirements for existence. 



Since trout br*eeders have to adjust the management of their fisheries to the habits 

 of the specific variety, we will discuss here the characteristics and habits of the 

 three foremost varieties, cutlvated at the present times. 



It is of course not always possible to adjust the conditions of pond fisheries 

 con5)letely to the most preferred natural conditions, but at times, fish will even grow 

 better under "unnatural" conditions. Still, the environmental ccnditions must be such 

 as to facilitate proper adjustment to the changed conditions and artificial feeding on the 

 the part of the fish. This question must be briefly investigated for each trout species 

 as given in the following text. Other fishes occasicMially raised with trout, such as 

 graylings, maranes, pike, salmon, etc., cannot be especially discussed here. 



2. Brown Trout, or Brook Trout 



The brown trout (Salmo trutta forma fario L. ) is at present the only important 

 native trout variety of all Middle Europe. To trout breeders, it is the trout, for short. 

 It was the first Middle European trout species to be artificially grown. 



Like all other salmonlds, the brown trout has a second dorsal fin, a "fat fin". 

 Orange-red spots, surrounded by blueish and white rings distinguish the brown trout from 

 the sea trout ( Salmo trutta L.), and from the lake trout ( Salmo trutta forma la custris L.) 

 (see Fig. 22). Coloring and bodily form are changeable, though, especially through 

 feeding. Even the red spots may be lacking but the silver glow of sea and lake trouts 

 is always absent. 



93 



