Dec, 1921 FOOD of ohio darters 55 



COMPAR.\TIVE FOOD HABITS OF DIFFERENT SPECIES. 



The darters belong to the family Percidas and so are most 

 nearly related to the perch and the pike perch. The darters 

 are a specialized group and so far as the food habits of the 

 young go, there is such a variety of behavior that it is difficult 

 to select a typical mode. The perch is a generalized fish on the 

 other hand and it is practically certain that the darters descended 

 from an ancestral perch-like fish. In seeking for a near relative, 

 therefore, with which to compare the darters we naturally turn 

 to the perch. In this fish there are three well recognized but 

 intergrading stages of food habit depending upon age. The 

 very young subsist almost entirely on entomostraca, turning 

 gradually to amphipods and insect larvae — mainly midge and 

 may fly larvae — while the proportion of entomostraca dimin- 

 ishes. Still later, in the yearling and two-year-old perch the 

 diet becomes very complex but there is a predominance of 

 amphipods and large insect larvae in the food. Snails and veg- 

 etable material are also eaten in considerable quantities. These 

 three stages in the food habits of fishes have been shown by 

 Forbes to exist in the perch and in many other fishes, especially 

 the Centrarchidae which are closely related to the darters and 

 they have been designated as infancy, youth and maturity. In 

 examining the records of the food of the darters to select those 

 showing a typical habit, the three periods are borne in mind 

 and those fish are selected which most nearly conform to this 

 type of habit. 



Of the eleven species examined, Percina caprodes most 

 nearly meets the specifications of generalization in its food 

 habits. The periods of infancy and of youth are well marked 

 and the period of maturity is marked by an omnivorous habit. 

 It would also be expected also that a fish with a generalized 

 food habit would find survival easy and would therefore be 

 abundant and uniformly distributed. All these requirements 

 are met, indeed the distribution of Percina was identical with 

 that of the perch in many places. 



Boleichthys may also be ranked as generalized in its food 

 habits. Beginning with entomostraca in the 12 mm. stage, it 

 changes rapidly to amphipods and insect larvae, never giving up 

 the entomostraca entirely even in the 50 mm. stage. Then it 

 passes to maturity, where the boundary is not so well marked. 



