Fig, 38. Group of step-like mast ponds arranged on a flat 

 slope in a trout fishery of the V/est German Secondary Mountains. 



Chapter VI 

 NATURAL PROKJCTIVIIY OF PONIJS, THEIR STORAGE 

 CAPACITY AND THE STOCKING OF PONDS. 



The aim of stock re^^ulation is to bring the number and weight of stock into proper 

 relations to the given chemical-physical and biological conditions. It is today one of 

 the most important means by which to increase production in quantity as well as quality. 



First of all, stock regulation shall bring forth a perfect adjustment of the stock 

 to the existing natural food conditions in carp and tench ponds. This even in case of 

 artificial feeding, the more so, since the amount of food, given to carp and tench is 

 depending again upon the natural food, available in a given pond. Only under intensified 

 culture is the adjustment of trout to pond conditions more in the nature of an adjustment 

 of chemical-physical-hygienic factors. The production rate is than chiefly determined by 

 the intensity of feeding. 



As mentioned already, the exact amount of stock per pond is to be calculated by 

 the weight and size of the fish, i.e. by the more nearly marketable sizes of fish, 

 especially for large carp extending and maturing ponds. And since through such calcul- 

 ations pond conditions shall approach the gross natural productivity of ponds as closely 

 as possible — feeding in carp and tench fisheries is based upon this natural productivity — 

 it becomes necessary, of course, to first ascertain the natural productivity of a given 

 pond. 



The gross natural productivity, namely the yearly weight increase of fish without 

 additional feeding can be estimated from previous experiences. (It is to be remembered 

 that new ponds are by 100 percent more "fertile" than older ones). Exact estimates of 

 the really available natural food (aquatics) will have to be done by the fish biologist. 

 The experienced fish breeder can only guess — more or less correctly — ^what the natural 

 productivity of a pond may be, taking into consideration the information in chapter IE 

 enumerating physical, chemical and biological factors, etc. (It is nov; generally agreed 

 to divide ponds into four classes from the viev/point of productivity.) 



Fisheries in moOrs and in heaths usually belong in the 3rd and ^ith classes (also 

 lime poor ponds), while fisheries upon light soil and lime rich ponds usually fall into 

 the second class. 



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