344 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



5 



3 A. 56 7 8 9 10 11 12 13 U 



Total length In Inches 



Figure 29. — Length-weight relation of 309 grayling from Grebe Lake, Yellowstone National Park, 

 unweighted average empirical weight within each H-inch length group. 



Dots represent 



measured volumetrically by water displacement. 

 Identifiable organisms were sorted, dried 1 to 2 

 minutes on blotting paper, and then measured in 

 the same manner as the total contents. How- 

 ever, the small amount of material in trout from 

 the tributaries and in the young-of-the-year 

 grayling precluded such measurement. The or- 

 ganisms most commonly used as food by Grebe 

 Lake fishes follow: 



OLIGOCHAETA 



Lumbricus terrestris 

 CRUSTACEA 

 Cladocera 



Daphnia (probably pulex) 

 Copepoda 



Cyclops sp. 

 Amphipoda 



Gammarus fascial us 

 INSECTA 



Plecoptera (identified by Dr. A. R. Gaufin, 

 University of Utah) 

 Alloperla sp. 

 Isoperla sp. 

 Peltoperla sp. 

 Nemoura sp. 

 Ephemeroptera (identified by Dr. George F. 

 Edmunds, University of Utah) 

 Baetinae (possibly Centroptilum) 

 Cinygmula sp. 

 Rhithrogena sp. 



Baelis sp. (possibly intermedins) 

 Ephemeralla coloradensis Dodds 

 Callibaetis sp. 

 Caenis sp. 

 Ameletus sp. 

 Odonata (identified by Dr. G. H. Bick, Tulane 

 University) 

 Zygoptera 

 Ischnura sp. 

 Lestes sp. 

 Argia sp. 

 Anisoptera 



Cordulia shurtleffi Scudder 

 Trichoptera (identified by Dr. H. H. Ross, 

 Illinois Natural History Survey) 

 Agrypnia deflata Milne 

 Limnephilus sp. 

 Myslacides sp. 

 Neothremma sp. 

 Molanna sp. 

 Agapetus sp. 



Rhyacophilus sp. (identified by Dr. H. C. 

 Chandler, California Department of 

 Fish and Game) 

 Coleoptera (identified by Dr. H. C. Chandler) 

 Malachiidae sp. 

 Staphylinidae sp. 

 Crenitis allicola (Fall) 

 Diptera 



Tendipedidae ( = Chironomidae) 

 Hymenoptera 

 Formicidae 



