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like the bullheads ; others learn to depend chiefly on molluscan 

 food — the sheepshead and the red horse species ; but many- 

 become essentially carnivorous. In fact, unless the gars are an 

 exception, as they now seem to be (attacking young fishes 

 almost as soon as they can swallow), all our specially car- 

 nivorous fishes make a progress of three steps, marked, respect- 

 ively, by the predominance of Entomostraca, insects, and fishes 

 in their food ; and the same is true of those strictly fitted for 

 a molluscan diet. 



PRINCIPAL ELEMENTS OF THE FOOD. 



An analysis of the facts made with reference to the kinds of 

 fishes eating each of the principal articles in the dietary of the 

 class, and showing the relative importance of these elements in 

 the food of the various species, will have its separate interest 

 for us, especially as it will exhibit the competitions of fishes for 

 food, and also the nature and the energy of the restraints 

 imposed by fishes on the multiplication of their principal food 

 species. 



The principal fish-eaters among our fishes — those whose 

 average food in the adult stage consists of seventy-five per 

 cent, or more, of fishes— are the burbot, the pike-perch or 

 wall-eyed pike, the common pike or pickerel, the large- 

 mouthed black bass, the channel-cat, the mud-cat, and the 

 gars. Possibly, also, the golden shad will be found strictly 

 ichthyophagous, this being the case with the four specimens 

 which I studied. Those which take fishes in considerable but 

 moderate amount — the ratios ranging in my specimens from 

 twenty-five to sixty-five per cent. — are the war-mouth (Chjeno- 

 bryttus), the blue-cheeked sunfish, the grass pickerel, the dog- 

 fish, the spotted cat, and the small miller's thumb. The white 

 and the striped bass, the common perch, the remaining sun- 

 fishes (those with smaller mouths), the rock bass, and the 

 croppie, take but few fishes, these making, according to my 

 observations, not less than five nor more than twenty-five per 

 cent, of their food. Those which never capture living fishes, 

 or, at most, to a merely trivial extent, are the white perch or 

 sheepshead, the gizzard shad, the suckers, and the shovel fish 

 4 



