I will attempt here, nevertheless , as an exaii9>le, to oalciilate the dally total require- 

 nont in actxial calories of a rainbow-trout of ICX) grams weight, in order to show that it can 

 be done, after all (the foodstuff components have not been considered). 



As seen from previous figures, the hourly caloric needs of a rainbow-trout amount to 

 60 gram-calories p^r 1 sqiiare decimeter body surface and at a water temperature of 15 degrees 

 centigrade, i.e., to 1.^ kilogram-calories per day, Thuss 



Body surface Iqdm (square decimeter) 



Water temperature 15 *C. (degrees centigrade) 



Calorie needs per hour *...... 60 gcal (gram-calories) 



Calorie needs per day 1.44 kcal (kilogram-calories) 



It is possible to calculate the body surface of a fish according to the fomula oft 



eq. 10 X p2/3 



Here stands for surface, expressed in qdm and p stands for weight in grams. In the 

 oase of a rainbow-trout of 100 grams weight, we would have the equation of: 



eq. 10 X 100^/3 ^^^ 21,54 qom eq. 2.154 qdm. 



Therefore, the daily caloric needs of this fish are (in state of hunger and at a water 

 tenperature of 15 degrees centigrade): 



B eq. 2.154 X 1.44 kcal/day eq. 3,1 kcal/day. 



According to Lindstedt, the metabolic rate — through feeding — increases by about 25 per 

 cent, raising the needs in calories, per day, to: 



3.1 - 0.78 eq. 3.88 kcal 



Assuming a proportion of 3:1 between caloric needs and metabolic rate, we find that a 

 rainbow-trout of 100 grams weight requires a daily calorie supply of: 



3.88 - 0.97 eq. 4.85 kcal. 



An analysis made by Koenig (table 4) shows that 1 gram of seafish meat or meat from 

 warm-blooded animals produces 1 kcal. 



It follows that a rainbow-trout of 100 grams weight and at a water temperature of 15 

 degrees centigrade requires, in round figures, 5 grams of seafish meat or meat from warm- 

 blooded a nimal s, i.e., 5 per cent of its own weight, daily. In other words/ a "Food per- 

 centage" of 5 per cent and which has been found correct by practical experience, and for 

 the purpose of conmiercial fish breeding (in waters of from 10 to 15 degrees centigrade). 



Crude Fiber and Other "Fillers". 



Crude fiber, such as cellulose, pentosans (semi-cellulose), lignln, cutin (the fatty 

 8\ibstance of the cuticula) is present in almost all artificial, vegetable foodstuffs. 

 These constituents are nothing but "fillers", and while lowering the concentrated strength 

 of the organic con^yonents of supplied foodstuffs, they act at the same time as a roughage, 

 thereby aiding the proper functions of the intestinal tract. An over-rich diet is not at 

 aU desirable. 



The addition of sawdust, of potatoe pulp, etc. to artificial, nourishing foodstuffs 

 has given good results in the feeding of trout. BotherscMne ailments, such as inflamation 

 of the bowels, cirrhosis of the liver have been thereby greatly reduced. On the other 

 hand, an excessive addition of "fillers" and "roughage" greatly lowers the nutritive 

 value of foods and reacts unfavorably upon the well-being of the fishes. 



24 



