126 CALIFORNIA FISH AND GAME 



runs have sliowii slirimp (Pif?. 35) to occur in enormous numbers 

 here, over 1000 bein": found in an area of one square foot. Snails and 

 chims are likewise very abundant and the trout a?ain prove them- 

 selves rank opportunists, eating what they can get, where they can 

 get it. It is interesting to note that only one snail and 150 shrimp 

 were eaten by the four rainbows from Hot Creek, tliis species appar- 

 ently preferring shrimp to snails and clams. With the Loch Levens 

 the reverse was true, the latter tish showing decided preference for 

 snails and clams rather than shrimp. The shells of the snails and 

 clams apparently pass through the digestive tracts of the fish without 

 harmful effects. 



Of the 56 caddis-flies eaten, only four were taken as adults, 52 of 

 them being aciuatie larvae and pupae. Damsel fly nymi)hs (Fig. 84) 

 which formed 2.5 per cent of their diet, are usually absent from the 

 swifter mountain streams, preferring rather the Aveedy margins of 

 quiet or slowly flowing waters. Their life cycle is similar to that of 

 the mayflies and stoneflies. They can always be recognized by three 

 long slender plate-like gills on the tip of the abdomen. 



In the case of the Hot Creek rainbows here reported on, 99 per 

 cent of their foods were aquatic in origin, just five items being terres- 

 trial in origin. 



In summary it is to be noted that the dominant foods eaten by 

 trout from the three streams reported on above, were mostly small in 

 size, except for the shrimps, snails, and clams, and large numbers of 

 each Avere consumed. Also, that the water supplied by far the majority 

 of food, land forms being comparatively scarce, except for leaf hoppers 

 found in the rainbows from the Merced River. It probably takes 

 about as much effort for a trout;to secure a large caddis-fly larva as 

 a small leaf hop])er, and when Over 100 leaf h()])])crs or fly larvae are 

 found in a single stomach, it is evident that that fish had been very 

 busy just previous to his demise. It is generally conceded that small 

 foods are eaten by small trout and though the average length of the 

 three lots of fish reported on here was only slightly more than six 

 inches, I have opened many trout up to fifteen and eighteen inches in 

 length that contained only such foods as were found in the stomachs 

 of these smaller fish. Larger fish will eat larger foi-ms such as cray- 

 fish, minnows, fingerling trout, etc., if they can get them. In many 

 streams, how'ever, large food organisuLs are lacking and the fish are 

 mainly dependent upon such everyday iniderwater sta])les as caddis- 

 flies, ma}"flies, true flies and shrimji. Last opening date on the Truckee 

 E-iver the 8- to 12-inch trout I caught Avere packed with just such 

 small underwater forms. One good-sized caddis larva Avill equal man}' 

 small mayfly nymphs in body weight. The latter forms make up in 

 numbers what they lack in size in most SAvift-water streams. Caddis- 

 fly larvae and other large foods are scarce in many streams Avhich 

 makes it necessary for the fish in such streams to eat the smaller foods 

 or go hungry. The above .stomach examinations shoAV that they do 

 just this, eating hundreds of small forms in lieu of a lesser number of 

 large foods. 



In conclusion, the data presents a l)ricf rcA'ieAV of the food of a 

 few trout from three streams. Due to lack of space, no attempt has 

 been made to giA^e any data on stomach examinations of trout from 



