122 



CALIPORXIA FISH AND GAME 



which ii()i-iii;illy live in 1hr water. Tlic i-ciiiaiiiiiiy l.'! per cent were 

 terrestrial in oiiizin tlial had fallen into tlie water accidentally. 



If we now examine tlie food of trout from a typical mountain 

 stream such as the ^Merced River, certain marked ditferences in the 

 selection of food becomes evident. 



In Table 2 is summarized the food of 10 rainbow ti-out taken 

 recently in the ^Merced River on the floor of Yosomite Valley.* Instead 

 of caddis-Hies being numerically dominant in the stomachs, wc f(jund 

 leaf hoppers to predominate along with beetles, there being almost as 

 many of the latter as of the former in the ten stomachs. 



Fig. 30. Larva and adult of riffle beetle. Twelve times actual size. 



Table 2. Foods Consumed by 10 Rainbow Trout from the Merced River in the 



Floor of Yosemite Valley * 



Number found Per cent 



Class of food inlOstomaehu of total 



Leaf hoppers 294 35.46 



Beetles 293 35.34 



True-flie.s 108 13.02 



Caddis-flies 61 7.35 



Mayflies 22 2.65 



Stoneflies 21 2.53 



Miscellaneous 30 3.63 



Total 829 



* F^isli taken Oct. 31 and Nov. 2, 1933. Average length, 5.5 inches; maximum, 

 8.3 in., miiiinnim, 4.05 in. 



Leaf hoppers are small insects, usuallj^ less than a quarter of an 

 inch long, often green in color, that live by the thousands on leaves of 

 trees and grasses adjacent to streams. Naturally, when as abundant 

 as they were this year, many fall or are blown into the water. As 

 many as 104 occurred in a single stomach and only one failed to con- 

 tain any at all. 



* Thanks are due C. G. Thomson, Superintendent of Yosemite National Park, 

 for his hearty cooperation in furthering our field investigations in the streams and 

 lakes of the Yosemite region. 



