DeRyke and Scott 45 



than on a mud bottom; the use of insect larvae was about the same in both 

 environments and the per cent using amphipods, cray-fish, insects, snails and 

 plants as food was greater on a mud bottom than on a sand bottom. 



GENERAL CONSIDERATIONS 



From the data collected during this period of investigation it is very 

 evident that the foods of young fishes as a rule are widely different from 

 the foods of the adult. It is not only different in the extremes between youth 

 and adult, but very marked periods in growth may be correlated with very 

 definite changes in food. In some species, as the perch and bass, there are 

 three very noticeable food periods. 



In the bluegills there are two such periods, while in the Etheostoma 

 caprodes (log perch), Labidesthes sicculus (skipjack) and Eupomotis gibbosus 

 (sunfish) we find a rather steady food habit of few changes. 



This fact of the relation of food to the age of the fish was pointed out 

 as early as 1880 by S. A. Forbes. The following extract from one of his 

 papei*s states very clearly his views on this point: "It was early apparent 

 in the course of investigation that the food of many fishes differs greatly ac- 

 cording to age, and it was soon found that the life of most of our fishes 

 divides into at least two periods, and of many into three, with respect to the 

 kinds of food chiefly taken. Further, in the first of these periods, a re- 

 markable similarity of food was noticed among species and families whose 

 later food habits were widely different." 



Many attempts have been made to provide artificial food for fishes. 

 This seems to have been a great outstanding problem which demanded solution 

 before the success of the fish culturalists could be assured. The American 

 Fisheries Society has spent much time and money on the problem trying to 

 solve it for economical purposes. Many investigators have worked on the 

 problem attacking it rather from the point of "what fishes will eat" than 

 from that of "what fish do eat." Many foods such as liver and prepared foods 

 have been tried regardless of the kind or size of fish to be fed, and failure 

 has resulted. This was experienced by Dwight Lydell ('06) at Mill Creek 

 Station, who attempted to feed a Chicago fish food preparation, and by several 

 others who have used liver and other foods in many different ways. 



Many successful attempts to feed fish have also been made but in prac- 

 tically every case the food that has been provided has been that to which 

 the fish was naturally accustomed. Mather ('96) was successful in raising 

 entomostraca for young fish, his only difficulty being to provide enough as 

 they used an enormous amount of this food. Large mouth black bass were 

 fed by O'Brien ('98) who used carp fry for the young bass and whose chief 

 difficulty seemed to be the rapid growth of the carp. Lydell ('02) used 

 Daphnia, Bosmina and Corixa and other small aquatic forms as food for 

 bass fry. Liver was fed to the adults during the summer, but "in order to 

 bring the fish through the winter in good condition it is necessary to begin 

 feeding minnows in September and to continue this until the fish go into 

 winter quarters." (1) In 1911 he successfully fed sucker meat, cray-fish and 

 clam meat. 



One of the chief factors entering into the problem is apparently the 

 difficulty of providing a balanced pond so that all the fish, old and young, 



