The "grading system", so necessary in carp raising, reqiiires a large series of 

 different ponds, such as spanning ponds, nursing and rearing ponda, ponds for adult 

 ilsh and also hibernation ponds, aside from a pond for the spaimers, 



PresuEiing that a fishery raises its own stock, the necessary pond area must be in 

 proper proportions to the requirements of the different grades, i.e. from the egg to 

 adult fish, and in proportion to the difference between stock taken out to stock put in. 

 In other words, the available space must be in proportion to the increase of stock of 

 fishes of the same year during the three years rearing period and in the following 

 proportions : 



35:315:900 eq. 1:9:29 



The proporticMis will fluctuate, of course, on account of the hazaixls and of the 

 losses incurred during the first year, and later on through the varying productivity 

 of the ponds and the greater voracity of the fish in the third year. For these reasons 

 we recommend to base such calculations upon the figures in table 11. 



Table 11. 



Year 



Kind of ponds in order of Part (in percentage) of 



successive requirements. total pond area. 



Breeding ponds 0.25j( 



Nursery ponds for alevins 

 -'- and fingerlings 2.75 



Ifursery ponds for fingerlings 



and yearlings • 10.00 



Rearing ponds for yearlings 

 2 and two year olds •« 23* 



Hibernation ponds • 3. 



Ponds for adults (2 and 3 

 . year olds •. 60. 



Ponds for spawners, etc 1. 



100. 



Local conditions will continuously make for alterations and adaptations of these 

 enumerated percentages, the more so since few large fisheries abstain from the sale 

 of stock. Some of them raise stock almost exclusively. 



With regard to the location of the different ponda it is to be remembered that 

 breeding ponds require fresh water, i.e. water which has not been used already in 

 other ponds. This is aost in^ortant in order to avoid diseases. Among larger fish 

 (in other ponds) there may always be some disease and parasite carriers and the water 

 from their ponds may carry germs into the brood ponds, even though they seemed healthy 

 when placed in the pond. 



Hibernation ponds and the ponds for spawners must be so located as to make constant 

 supervision possible and to discourage fish thieves. 



79 



