474 Rouscz'clt Wild Life Bulletin 



THE FOOD OF THE NATIVE REDTHROAT TROUT 



The habits of fishes are as varied as those of terrestrial animals. 

 Fish are carnivores, first of all. But the dififerent kinds of fish have 

 their preferences in the way of food. A silver bass is primarily a 

 surface feeder, that is, he prefers to pick his food from the water's 

 surface or from plants near "the surface. Both the large-mouthed 

 and small-mouthed black bass are chiefly plant feeders, ' selectirig 

 their food from plants, while the crappie is more or less an indis- 

 criminate feeder, although he really prefers the muddy bottoms. 

 The trout, in general, are clean feeders ; that is to say, they do not 

 like to skim the bottoms, but prefer to catch, their prey when the 

 latter moves through the water. 



In mountain trout streams the rapidity of the current limits the 

 make-up of the fauna to such animals as are adapted to withstand 

 strong currents. In rapids one finds no leeches, no worms (except 

 flat-worms), no air-breathing insects, nor crustaceans (crayfish, 

 water-fleas, etc.). This limitation means that the food supply is 

 confined to such plants and animals as can withstand the strong 

 current either by strong clinging or propelling devices. It also 

 means that the fauna consists of relatively few species, which gen- 

 erally are present in enormous numbers. It means further that the 

 diet of the fish inhabiting such streams is limited to these items 

 primarily and that, humanly speaking, the diet must become 

 monotonous. 



The food of trout can be conveniently classed into two types : 

 zi'oter bait, which is the normal supply found in the water, and 

 surfeiee bait, consisting of insects and other animals that have fallen 

 into the water and become ''water trapped." This latter condition 

 applies when an insect's wings become water-logged or . so adhere 

 to the surface that the insect cannot rise from it. This surface bait 

 may be of various types, such as ants, grasshoppers, beetles, moths, 

 butterflies, — in fact, anything that a sudden gust of wind may carry 

 onto the surface. It may even include frogs, mice, worms, and other 

 stray land animals. 



The Water Food. — The normal food of trout streams, com- 

 prising the water bait, is represented in the main by three groups. 

 Named in the order of their importance, for trout streams only, 

 these are the Perloidea or stone-flies, the Ephemerida or ]\Iay-flies, 

 and the Trichoptera or caddis-flies. 



Stone-flies. — The Perloidea or stone-flies are the most conspicu- 

 ous fish food item in the Yellowstone streams. In this respect, these 



