The net yield is calculated from the gross jrield by the subtraction of all expenses, 

 of the initial costs, including the wage requirements of the contractor. It is subdivided 

 into a revenue portion, an interest portion, and a third portion which is the "rental from 

 the land". It is the monetary expression of the economic success of a management consider- 

 ed free of debt, and can at all times be used for the defense of one's rights against out- 

 siders. The calculation of the net yield per hectare (2.4-7 acres) enables one to judge 

 whether a certain tract of land had best be used for pond culture or for agriculture. 

 It is furthemore possible for the pond manager to determine from the figures, the pro- 

 duction costs for 50 kilograms (110 pounds) and so decide for hlmseLf as to the lowest 

 sellinr; price he can set without additions, a determination which is often verj' important. 



According to Bruening it is quite impossible to give a generally valid grasp of 

 workinr; costs, the local conditions are too greatly variable: the bookkeeping must give 

 the information. The rule is probably generally true, that the working costs are lower 

 in intensively conducted carp pond industries in which for 1930 the working costs for 

 30 kilograms (110 pounds) of carp growth increase were reported to be about 40 to 60 marks 

 (:J9.52 to 214,28), than they are in extensively conducted operations where the property 

 values are placed too high. In one case in 1931, von Debschitz announced an actual pro- 

 duction cost for 50 kilograms (110 pounds) of carps of 60 marks (§14.28) by utilization of 

 all intensifying possibilities, of 57 marks ($13,57) with fertilization without feeding, 

 and of 77 marks (S18.33) with natural operation. 



The annual balancing of accounts makes it possible, furthermore, to decide whether 

 the developnent is going upward or downward. It may at the same time be determined if 

 the reason for a change of the natural gross jrLeld is to be sought in unusual weather 

 conditions, or in the market conditions for table fishes, stock fishes, foodstuffs, and 

 fertilizers. Bookkeeping assists the memory of the pond manager. 



It is also of very special value in the consideration of economical precautions. 

 The success of various methods of stocking (see Chapter VI), feedir^js, and fertilizacions 

 can.be judged by the achieved growth increase. It is therefore best to provide for each 

 pond a book of receipts and expenditures and also tabulations with the following columns; 



(1) Stocked on, number, kind, weight (vrith small stock fishes, the lengths), 

 place of origin, 



(2) Fished out on, nunber, kind, and weight of fishes, shipped to. 



(3) Food, fertilizers, reed clearing, soil cultivation, pond treatment. 



To make ccmiparisons possible, the yearly accumulated figures must naturally be 

 converted to a unit common denominator. For carp and tench ponds, therefore, a further 

 tabulation must be calculated: 



The piece loss per pond and in percent, the fish grovvth increase per pond 

 and per hectare, separated into natural increase, food increase, and 

 fertilizer increase and with feeding, the food quotient, 



I an acquainted with pond managers who prepare these figures graphdcallj- year after 

 year and thereby draw valuable concliisions in regard to the profitability of feeding, 

 soil cultivation and reed clearing. At the top of each pond tabulation, statements are 

 made on the size and depth of the pond, filling and running out time, and about the con- 

 version factor for calculating the yield per hectare from the yields for the pond, 



!Jaturally these many calciilations require much effort and time, but they are extreme- 

 ly important for a well planned management. In smaller managements they can often be 

 regarded as unnecessary. There the bookkeeping must be as simple as possible for a quick 

 convenient survey. The greater the management is, the more detailed must the bookkeeping 

 be constructed. 



Under some circumstances and especially also v/ith the cash books, special Cv^culation 

 must be opened for the individual branches of operation, such as carp, tench and trout 



189 



