Fig. 19. Drainage of a standard 2 hectar Nursery Pond, 

 A firm completely drainable bottom with grain stubble. Carp and 

 Tench brood are driven forward in the fish ditch, by a stidc, to the 

 sluice (front right), and thence into a trap box outside of the pond 

 to be fished out. 



The most important task for any hatchery is to look after the health of the brood. 

 Aside from prophylactic measures against contagion from parasites and other disease 

 germs — ^which may enter brood ponds from inflowing water or may be spread through the 

 invasion of larger fish — the strengthening of resistance of the brood plays the most 

 important role. 



This is possible by providing proper natural food and in such quantities that the 

 brood can fully satisfy their appetites up to and until the very last day of their so- 

 journ in these ponds. The idea being to foster a rapid growth during the first few 

 weeks, since the most dangerous period of the brood for eventual afflictions (Dactylog- 

 yrus, Costia, Chilodon, Ichtiophthirius) is the time when the young fish are only 5 to 

 6 centimeters long. 



It is from this viewpoint that the Qibisch method — i.e. transfer from spawning 

 ponds into nursery ponds — is the best guaranty against the dangers, besetting the brood. 

 In the nursery ponds they can fully satisfy their appetites (provided rational stocking 

 of the ponds is adhered to) during the first few weeks. 



Nursery ponds are really the best prophylaxis against brood diseases, but they re- 

 quire constant care and supervision by an experienced fish breeder in order to bring 

 results. The following rules are to be especially observed: 



(1) Nursery ponds are to be filled up only after the brood has emerged from the 



eggs, i.e. five days after the filling up of the spawning ponds. Walter (1926) 

 had best results from this procedure. This waiting time allows for the develop- 

 ment of sufficient quantities of Infusoriae and even of Bosminae . Chydorus . 

 Eudorina . etc., (the main food of the brood up to 7 or 8 mm. length) and at the 

 same time prevents an accumulation of predatory insect larvae. Tadpoles will 

 later on appear, nevertheless and will greatly interfere with a fishing- out of 

 the brood. How to deal with these pests will be found later on in this book. 



84 



