3. Artificial Food Supply 



Feeding of pond fish, in addition to the food provided for then by nature, is seldom 

 done today, with exception made for the rearing of trout in hatching tanks. 



As indirect, additional "ai-tificial" feeding nay be regarded as artificial encroach- 

 ments upon the processes of disintegration (fertilizing, soil improvements, clearing away 

 of reeds, etc.). 



In table 3, one will find the most important and in practice most suitable fish food- 

 stuffs. The general differences of such foodstuffs, as regards carp-like fish and trout 

 will also be noticed. The selection of such foodstuffs depends, of course, upon the highly 

 variable factors of times and prices. These inay vary frjm year to year. In the case of 

 carp and of carp-like fish, which do not properly consume their food, the price of food- 

 stuffs is of greater importance than the con5)osition of the same, provided the whole diet 

 does not consist of fran 50 to 70 per cent of natural food. In regard to trout- like fish, 

 the temptation of low prices must not outweigh the consideration that trout require food- 

 stuffs which will assure their s'ostenance and well-being to the extent that they will not 

 have to rely upon natural food, i.e., they will not have to hunt for food, 



A. Nutrition and Digestion 



Nutrition experiments have repeatedly shown that a specific selection of food animals 

 for each individual fish species does not take place. Pond fishes at least are extensively 

 omnivorous in regard to small animals. In the crowded contraction of the living spaces of 

 the bottom of the plant world (shore), and of the open v.-ater, it is understandable if the 

 shore-feeders take up abundantly occurring bottom or open water animals as a welcome 

 opportunity nutrition. Furthermore, in regard to taste, the nutrition-animal world does 

 not show great differences (except with mites and strongly chitinized animals) which would 

 cause a selection of special forms. 



On the other hand, the feeding of fish is greatly influenced by certain mechanical 

 factors, i.e., their abilities to take hold of, and to sv;allow the available supplies. 

 Their physiological equipments in regard to senses also plaj-s a role here. Both ol these 

 factors vary among the different species. 



In regard to insect food, fisn are more or less omnivorous. Trout and all predatory 

 fish, such as pike, perch-pike, and perch grab their prey, lightning-like, with their well 

 dentated mouth and sr/allov; it whole, Trichoptera, for instanc, are gulped down vdth their 

 "quivers" (shell case), which can be felt against the stomacli 7/alls by mere outside examin- 

 ation of the midriff section of the fish. On the other hand, carp will dig larger larvae 

 out of their "cases". It is this mode of feeding, combined vdth the pointed (acrocoirpous 

 formation) of their mouth vrtiich makes it difficult for predatory fish to feed upon deeply 

 imbedded organisms in the ooze of the bottom, and forces them to seek freely placed or 

 moving forms. 



In contrast to the predator/ fishes, the Cyprinides (carp-like fishes) by means of 

 their proboscis-like, extensible, tootr.less mouth, take up bottom animals from which the 

 adherent inud is moi-e or less completely spat from the mouth by backward rinsing motions. 

 The frequent high detritus content of the intestine shows the incompleteness of the 

 cleansing process. The carps, tenches and related fishes therefore show an excellent 

 evaluation of mud-dwelling animals. 



Size and body shape also play a certain role in the successful hunting for food. 

 Certain fish are thereby enabled to make their way into vegetation tickets, explore 

 shallow shores, etc. The pharyngeal teeth in fish (according to T.undsch 1931) serve merely 

 to crush the food, and probably also to "peel" lupine seeds and expectorate the shells un- 

 eaten . 



In regard to the physiological abilities of percention. vfe have to distinguish between 

 "eye fish" and "nose fish", i.e. betv/een fish that rely chiefly upon their sense of vision 

 in their hunt for food, and those wldch are directed to their food by the olfactory sense 

 and partly also by taste. 



P-7<»0» 



15 



