166 



BULLETIN OF THE BUREAU OF FISHERIES. 



Greenback trout (Salmo stomias). — The stomachs of 72 greenback trout were 

 examined. Eight of them were empty, leaving 64 to be accounted for in the table. 

 Of this number, 18 were obtained from Upper Lake, 1 from Lower Lake, and 53 

 from the pool below the dam. 



Contents of stomachs of 64 greenback trout. 



V 1 elements. 



Number 

 hi speci- 

 mens 

 in which 

 found. 



Fish remains 4 



Orthoptera 7 



Hemiptera 2 



Trichoptera - 1 



Lepidoptera (moths) 14 



Diptera 29 



Average 

 per cent 



of 

 element. 



7n. ii 

 59. 7 

 i. .ii 

 10.0 

 12.0 

 30.8 



Fi.Oll i-lrliiellK. 



Number 



i.i speci 



nuns 



in which 



found. 



Chironomus (larvse and pupae) 10 



Coleoptera 25 



Hymenoptera (antsi 5 



Insect fragments 29 



Crustacea ( Entomostraca) 11 



Vegetable debris 7 



Average 

 per cent 



ni 

 element. 



17.7.-) 



42.7 



19.4 



51.7 



77.0 



3S. 4 



Specimens from all three localities contained Daphnia. One stomach contained 

 4,500 Daphnia and another 2,250. Two of the specimen-- had eaten both copepods 

 and Daphnia, hut the other 12 of the 14 that had eaten Entomostraca contained 

 Daphnia only. 



The vegetable debris consisted chiefly of Potamogeion leaves. 



A feather was found in one .stomach and a few pieces of twine in another. 



Jordan (1891) says, concerning the food of this species: "At the hatchery of 

 Dr. Laws, it appears that this trout will not willingly eat young suckers and 

 minnows, its food being largely young crustacea." It will be noted in the above 

 table that only -i stomachs out of til contained remains of fishes. 



Rainbow trout(Salmo iridt us shasta). —The stomachs of 111 rainbow trout were 

 examined. Out of this number 8 were empty, 36 were estimated to be a third full 

 or more, and the other 70 a quarter full or less. The specimens varied in length 

 from 6 to 18 inches (15 to 45 centimeters). Twenty-two of them were caught in 

 Upper Lake, 21 in Lower, and 68 in the pool below the dam in the outlet canal. 



Content!! of stomachs if 106 rainbow trout.  



Pood elements. 



Mammal remains . . 



Fish remains 



Araneida (spiders) . 



Odonala 



Orthoptera 



Hemiptera 



Trichoptera 



Lepidoptera I moths 

 Diptera 



N umhei 

 of speci- 

 mens 



in which 

 found. 



Average 

 per cent 



of 

 element. 



42.0 



07.3 



10.0 



2.5 



4.3 



2.6 



4.7 



13.6 



8.9 



Food elements. 



Chironomus (larva and pupae) 



Simulium ( larva?) 



Coleoptera 



Hymenoptera 



Insect fragments 



Crustacea 



Mollusca 



Vegetable debris 



Sand and gravel 



Number 



ol si I- 



mens 



in which 



found. 



A verage 

 per cent 



of 

 element. 



10.3 

 !..s ;; 

 22. 2 

 5.6 

 55. 1 

 37.3 

 inn 

 35. 6 

 41.8 



About a fourth of the fish remains were positively identified as remains of young 

 suckers (C. commersonii) but the rest were not recognizable. These results do not 

 agree with the observations of Chambers (1887), who states that the rainbow trout 

 introduced into England "is more delicate in its appetite than other varieties of Sal- 

 monidse, and therefore is not prone to the same temptations to cannibalistic attacks 



