508 U. S. BUREAU OF FISHERIES 



In general, all of these lakes contain a limited supply of food, 

 probably due to the short growing season and the low lime content 

 of the waters. Some of the rock-rimmed lakelets at the higher 

 altitudes were considered unsuitable for trout because of the ex- 

 tremely limited food supply. The boggy-shore lakes were held to be 

 unsuitable if tributary streams were lacking, and the process of 

 filling had advanced too far. However, a good proportion of these 

 types, as well as the type intermediate betAveen them, should provide 

 for a limited number of trout. The reservoir type is considered 

 suitable for a moderate number, depending upon the level to which 

 the waters are reduced. 



The only fish native to the region and naturally present in lakes 

 not separated by impassable falls from lower waters is the cutthroat 

 trout, Sahno j)^ewiticus Cope. No forage fish such as minnows and 

 whitefish were observed in any of the lakes, and their introduction is 

 considered as a possible means of improving production. Many of 

 the lakes were formerly barren of all fish life. Rainbow, eastern 

 brook, and Yellowstone cutthroat have been introduced into some 

 of these lakes, and where the plantings were moderate have made 

 good growth. Food studies of 153 specimens of trout of lakes show 

 no noticeable difference in diet among the species represented, the 

 food taken by native cutthroat, eastern brook, and rainbow consist- 

 ing of 25 per cent terrestrial and 75 per cent aquatic organisms. 

 Midge larvje, pupse, and plankton Crustacea comprised the bulk of 

 the aquatic food ; ants, the bulk of the terrestrial food. 



Stream, studies. — Five drainage s}' stems are located in the Wasatch 

 Forest : Provo, Weber, Bear, and Duchesne Rivers and Rock Creek. 

 The headwaters of these streams are very rapid and the pools are 

 narrow, shallow, and infrequent. The pH varies from 5.1 to 5.6 

 and the bicarbonate content from 7.3 to 12.6 parts per million ; food 

 organisms are extremely scarce. In their lower reaches, near the 

 forest boundaries the gradient becomes less steep, the pools improve 

 in type and abundance, and the fish food undergoes a marked in- 

 crease. The latter appears to be associated with a marked change 

 in the solution content of the waters due to the occurrence of lime- 

 stone outcrops within the drainage area at the lower elevations. 

 The bicarbonate content of the streams below 8,500 feet elevation 

 varies from 18.3 to 56.7 parts per million. 



Stomach examinations of stream trout showed a larger percentage 

 of terrestrial food in the case of cuttliroat trout and eastern brook 

 trout than was consumed by these species in the lakes. As in the 

 case of lake fish, ants formed the bulk of the terrestrial food. Caddis 

 larvae made up 35 per cent of the food of stream trout, with may- 

 flies, midges, and stoneflies next in order of importance in the aquatic 

 food list. One sculpin and one young trout had been taken bv these 

 fish. 



The principal conclusions to be drawn from the stream studies 

 is that stocking of trout should be largely confined to the lower 

 waters where food and pool conditions are suitable, but detailed 

 tables of the species, sizes, and numbers of fish and the frequencies 

 of planting in the various waters have been prepared for the use 

 of the fish-cultural staff. 



