FOOD OP THE SHORE FISHES OF CERTAIN WISCONSIN LAKES. 283 



insects are of much less importance than immature stages. The fishes feeding on ento- 

 mostraca (cisco, bream, crappie, perch, carp, etc.) are partly adults and partly young 

 fishes which will later turn more to other foods. In spite of the fact that these little 

 crustaceans are an important element in the food of most young fishes, they do not 

 rival insects. The total amount of insect food (36.3 per cent) in Table i is nearly twice 

 as great as the total amount of entomostracans (19.1 per cent). The piscivorous species 

 (pike, gar, pickerel, bowfin) depend on small fishes which get their food from plants 

 directly or indirectly through entomostracans or insect eaters. Scavengers (sucker, 

 blunt-nosed minnow, etc.) get organic remains from the mud and debris at the bottom 

 of the lake or among the aquatic plants. Doubtless, fishes affect each other to a con- 

 siderable extent by eating spawn. The perch in Lake Mendota follow the breeding 

 suckers and ciscoes inshore and eat their eggs. Table i shows that four species eat the 

 spawn of other fishes. Without doubt this number could be incraased by more extended 

 examinations during breeding seasons. 



The nature of the food influences the flavor of fishes, thus enhancing or decreasing 

 their desirability as food for man, and some particular kinds of food seem to make fishes 

 more or less palatable. One of the best food fishes in Wisconsin lakes is the wall-eyed 

 pike, which feeds on fish and frogs. The pickerel is also of good flavor and likewise eats 

 fish, but the bowfin and gar, though they feed mostly on fish, are most undesirable for 

 food. All fishes feeding largely on entomostracans or insects (and which attain suffi- 

 cient size to be eaten) are of good flavor. Feeders on vegetation or mud are in general 

 less desirable than carnivorous or insectivorous species. 



Little is known concerning the amount and variety of food required by fishes. 

 Putter (1909) did some work along this line, and rations on which certain species 

 thrive have been worked out in hatcheries, but there is no general satisfying knowl- 

 edge concerning the amount of food required, the variety necessary, the value of differ- 

 ent kinds of foods for metabolism, the rate of digestion, the percentage of foods digested, 

 and other matters relating to the value of foods. 



In its broad relations the matter presented in this paper is preliminary to more 

 important studies which should be made on the food requirements of fishes. The prob- 

 lem for the fish culturist and scientific investigator involves work in a number of differ- 

 ent fields. The food and feeding habits of fishes must be thoroughly known. The 

 work of Forbes and that presented in this paper contribute in this connection to a knowl- 

 edge of the fishes in the United States. Another line of investigation must be in 

 the chemical nature of foods. Studies are now being carried out by the Wisconsin 

 Geological and Natural History Survey in which adequate quantities of different species 

 of aquatic organisms are being analyzed. It will also be necessary to determine many 

 things relating to the general metabolism of fishes — amount of food necessary, kinds of 

 food necessary, rate of digestion and assimilation, what proportion of food eaten is 

 digested, etc. When all these things are known, it will be possible to ascertain definitely 

 why fishes thrive on certain kinds of foods and fail to do so on others. It will also be 

 possible to prescribe proper rations with some confidence. The recent work on the 

 etiology of beri-beri and the illuminating researches of McCollum and Davis (1915) on 

 the causes of growth open up new possibilities. These investigators have made very 

 exact determinations of the substances and amounts necessary for proper rations, and 

 the methods employed may be applied to fishes with profit. 



