PliOGRESS IN BIOLOGICAL INQUIRIES, 19 33 373 



previously obtaiiuHl ami niacle possible the preparation of several 

 papers for publication. 



QUANTITATIVE FOOD STUDIES IN MOUNTAIN STREAMS 



Nuniorous samples of bottom organisms were taken from square- 

 foot units of bottom in four mountain trout streams in the vicinity 

 of Salt Lake City, using methods developed by Dr. Needham, of 

 the Bureau's start". The purpose of these studies was threefold: 

 to determine the variation in food supply at dirt'erent elevations in 

 the same stream and in different streams; to study the fluctuation in 

 numbers and weight of bottom organisms in three streams during the 

 months of ,July, IVugust, and September; and to secure some infor- 

 mation as to the relative productivity of trout streams in this region 

 as compared with those studied in other parts of the country. 



Fifty-three scjuare-foot samples, taken in the rittle areas where 

 the bottom consisted of gravel and small rubble, showed great vari- 

 ation both as to numbers and total w^eight of organisms in dirt'erent 

 streams. Since other environmental conditions were similar, higher 

 temperature was considered responsible in certain waters for the 

 l?roduction of greater variety and quantity of food. Caddis flies and 

 may flies were found to be dominant organisms in these mountain 

 streams. 



Samples taken at elevations from 4,400 to 7,500 feet on one stream 

 and from 5,700 to 7,000 feet on another showed no appreciable dif- 

 ference in weight over the average for each stream. 



The studies also indicated that the food supply for any stream 

 is not constant for the summer months. In one stream a rise in 

 weight of samples occurred in August, followed by a decline nearly 

 to the July level in September. In another an increase in weight 

 was noted "throughout the summer. In the third, a marked decrease 

 in the average weight of samples occurred in each successive month. 

 On the other hand, all three streams showed a marked increase in 

 the number of organisms in August, followed by a decrease in Sep- 

 tember, which, however, did not reach the July level. This indi- 

 cates that August is probably the best month for planting small 

 trout in our mountain streams as the smaller organisms are most 

 numerous then. 



The average wet weight of the 53 samples was found to be 1.18 

 grams, although the average for the 3 streams studied monthly was 

 1.69. These averages compare very closely with those for trout 

 streams of New York and California having a similar type of 

 bottom. 



The results of this investigation were presented at the fall meeting 

 of the Utah Academy of Sciences and will appear in abstract form 

 in the proceedings of this society for 1933. 



COOPERATIVE IN^'ESTIGATIONS 



Through the cooperation of the Utah Fish and Game Department 

 in defraying field expenses and furnishing assistance, limnological 

 studies were made of three important fishing waters for the purpose 

 of developing better plans for regulation and planting. The Divi- 



