The ponds are to be filled only after the water tenperature lies continually over 

 15 degrees centigrade and does not drop all too much during the nights (in Germany this 

 means usually not before May 15), since eggs as well as brood are highly sensitive 

 against low temperatures and great changes in the temperature. It is reccmmended not 

 to begin with the filling of the pond during the early morning hours, but to wait until 

 the bottom of the pond has had time to warm up somewhat through the action of the sun. 



The spawners are brought into the Dublsch ponds as soon as the ponds are filled up. 

 Up to now, the two sexes have been kept separated in special spawner pcands (the female 

 can be recognized by a cone-like, reddened torus, the ^/agina of the fish, so to spea«, /( 

 and by a greater corpulence). These ponds must be kept well tempered — not too cool and 

 not too warm — so that the eggs may properly mature. There should be more spawners than 

 necessary to provide a reserve in case of failure. 



Great care is to be taken in the transfer of the spawners from their ponds into the 

 Dubisch ponds. At great distances, they are best transferred in water, at shorter dis- 

 tances they can be carried in wet clothes or upon burlap covered stretchers. (The belly 

 of the female, when ready to hatch is very soft, and roxigh handling of the male can 

 interfere with its ejaculation which should occur quite easily). 



Immediately preceding the transfer of the fish into the Dubisch ponds, external 

 parasites, adhering to their skin or scales are completely removed with a pair of dull 

 tweezers. In order to remove microscopically small skin and gill parasites, it is 

 advisable to rinse the spawners in a 2,5 percent salt solution for about fifteen minutes. 

 This does not interfere with the ability to spawn. 



Under a system of rational selection, only one pair of spawners is put Into each 

 pond. It is the generally prevailing custom, though, to put 1 to 3 sets of spawners into 

 a small pond of 100 square meters (one set cc«nprises 2 males and 1 female). I know of a 

 fishery which regularly puts ^0 spawners in their Dubisch pond of 1 Morgen size (about 

 2/3 of an acre). That is simply waste, traceable to the highly unsuitable size of the 

 pond. 



The spawning — also called stripping — usually begins shortly after the storing of tlie 

 pond or on the following day, under animated swimming to and fro of the spawners, Tlw 

 spawners have been "duped", so to speak, into spawning through the transfer from the 

 cooler ponds into the relatively warmer Dubisch ponds, and also through the bringing to- 

 gether of the two sexes, 



According to Hoffer, the ovary of a female of from 2 to 2.5 kilograms weight carries 

 from ^100,000 tc 500,000 eggs, (in an eleven-year-old carp of 8350 grams of weight and 

 72 centimeters of length, I counted 860,000 eggs.) 



It is quite true that even under the most favorable circumstances only about half 

 of this number will be hatched. 



The eggs are glass-clear, of a diameter of about 1.5 millimeter and are pasted upon 

 the prass or other plants (Fig. 17). IVhenever possible, the parent fish should be taken 

 out of the Dubisch ponds immediately after spawning and before the brood leaves the eggs. 

 In larger ponds this is best done by a quick drainage of the ponds — followed by immediate 

 refilling and restoring — during the cool evening or morning hours. 



Although the ponds will be dry for frcm 4. to 5 hours, this will not hurt the eggs 

 at all. In large ponds, not provided with ditches, the spawners can be fished out with 

 wide-meshed nets. 



This removal of the parent fish is a propl^lactic measure. Like the "bathing", 

 referred to above, it shall protect the brood from eventual contagion throxigh diseases 

 or disease genns of the parents. 



It is precisely in spawn ponds that germs and parasites find the best opportunity to 

 settle upon the new carp generation, if these safety measures are neglected. 



81 



