We have then the divisor 1000 "♦" 2 x 350 = 1700 grams and have thus the quotient 

 of 300 . 177. Hence, the "stock figure" is 177 x 1 for 2 year old carp and 177 x 2« 



1.7 

 35A for yearlings. 



As seen in table 17, the increase per hectar changes Immediately upon deviation from 

 2 year stock with normal stock weight and ditto increase. This allows the fishbreeder to 

 better the "hectar increase" through rationalization in stocking, proper choice of added 

 stock (from the viewpoint of weight) and use of mixed stock, according to general require- 

 ments . 



Highest results will not be achieved imder conditions as enumerated in table 17. Itie 

 figures in table 17 are rather a con^jromise between market demands, technical possibilities 

 and atteii?)ts for possible best results. 



Tne possibilities of a still better utilization of the natural foodstuffs, present In 

 a pond, depend upon the following fundamental principles, casually mentioned be fore » 



(1) Ponds will yield profits (per hectar) In correlation to the number of fish 

 per hectar (density of population) and according to the diversity of their 

 number as to quantitative and qualitative utilization of food, that is, to 

 the diversity of their size and characteristics. These factors will 

 foster proper food utilization. 



(2) The rate of profits per hectar will vary according to the rate of upkeep 

 (expenses for food). The cost of upkeep mounts in proportion to the 

 number of fish per space unit and decreases in relation to their more 



or less speedy increase in growth. 



It follows, that from the practical viewpoint one must strive to raise the possibly 

 greatest number of fish per hectar (density) but exercise the greatest possible economy 

 in the matter of upkeep. Too small a number of fish per hectar (low density rate) will 

 quickly increase in size and weight but at a disproportionally high rate of upkeep. 

 Fullest utilization of a pond's productivity calls for corresponding number of good 

 eaters. It is from this viewpoint that we arrive at the following rules for proper 

 stocking, and which ought to be kept in mind at all times. 



(1) At an expected high increase in weight, the number of fish per space unit 

 (density) will have to be correspondingly low. In less productive ponds, 

 the demands for weight increase should be low with a correspondingly low 

 density rate. 



(2) All too big 2 and retarded 3 years old carp do not repay the costs of 

 upkeep, since their necessary sustenance is out of proportion to their 

 increase in weight. This is particularly true for poor ponds. 



(3) The more favorable the natural food conditions, the easier can larger 

 stock fishes (despite their high maintenance requirements) find so much 

 natural food that they will reach an individual increase of 200 percent, 

 which alone guarantees a good food evaluation. V7alter has shown that 

 the piece weight of set-in fish can be greater, the more fertile the 

 ponds are. 



(4) A mixed stock of carp and tench and of various age classes has, on the 

 one hand, the purpose of better evaluation of natural feeding by enlarging 

 the extent of nutrition. On the other hand, the addition of younger age 

 classes to older ones in the large maturing ponds Increases the number of 

 feeders per hectar or maintenance requirement without strong Increase of 

 the total set-in weight. By this means an increase of the surface yield ie 

 achieved especially in the more extensive surfaces. 



129 



