to let the ■'..■ater laM into the pond throu-h a cla^ pipe. In trout ponds, if the fall is very 

 sioall, a horizontall.v placed screen on four rods is bailt in undtr the outflow of the clay 

 pipe, thus preventing trout fr-m jumping into the pipe. At tlie saae t.Lnie the water is finely 

 divided and enriche.. v,lt!-i oxygen. Spavming ponds must be protected, il* necessary, against 

 penetration of fishes and fish foes, by means of gravel filters (li^. C) v;hich are built in 

 ■vn.de portions of the v.ater inlet. Overflov/s for leading off water from one pond to another 

 should be provided vilth horizontal sieves. They must be placed so that trout rising froi.; tlie 

 under pond car. not injure their dorsal fins vxher. they enter the overflov; aiid "et under the 

 sieves. I.'aturally, glazed clay pipes may be built into the daia at the vater level. They are 

 closed at one end by attached sieves. 



rig. 8. A siriiple filter erected in the v/atcr inlet for the 

 detention of fish.-s and fish brood and for superficial water cleansing. 



iP?TR(j|i*- 





-*l»i:- 



FiC. 9' Overflov/ for connecting groups of trout ponds in series. 

 The separation of the ponds takes place by horizontally or obliquely 

 placed sieves of perforated or slitted netal sheets or by rod grids 

 placed in the direction of the vrater flow. liach pond '"las its ov.n sluice. 



65 



