PROGRESS IN BIOLOGICAL INQUIRIES, 1933 365 



Field studies. — A quantitative study of rainbow trout production in 

 a small spring-fed stream near Leesburg, Va., was made by Mr. 

 Surber. This stream has been turned over to the Bureau by the owner 

 for experimental purposes, and all fishing except by authorized per- 

 sons is i)rohibited. Trout are prevented from leaving the stream 

 by a revolving screen at the lower end. However, owing to severe 

 floods, the operation of the screen during the fall and winter of 

 1932-33 was so spasmodic that it is believed that the screen had 

 little effect in retaining the fish. 



A total of 49 pounds of fish, over 7 inches long, were removed 

 from the stream during the season, or an average annual production 

 of approximately 30 pounds per acre. It is known that a number of 

 large trout were left in the stream so that the total production was 

 undoubtedly somewhat greater. A study of the stomach contents 

 of these fish shows that although amphipods and aquatic insects 

 were abundant, the trout during the summer fed almost entirely upon 

 terrestrial insects. 



In connection with the field work at the Pittsford station, an 

 arrangement was made with the Middlebury College, Middlebury, 

 Vt., for the development of a program for improving trout fishing 

 in the streams under the control of the college. Most of these streams 

 are in the Battell Forest, a beautiful tract of over 30,000 acres, 

 located on both slopes of the Green Mountains. Owing to the limited 

 funds and personnel available for this work during the summer of 

 1933 it was only possible to make a preliminary investigation of the 

 more important streams in the forest. A more complete study of the 

 streams to be followed by a systematic program of stream improve- 

 ment will be undertaken in 1934. 



During the summer of 1932 a number of marked yearling brook trout 

 were liberated in an excellent trout stream adjoining the hatchery 

 grounds at Pittsford to determine if domesticated fish could care 

 for themselves under natural conditions as well as wild fish and also 

 if they would afford equal sport to the angler. The results were of 

 such interest and value as to suggest the advisability of conducting 

 a similar experiment with rainbow trout. Accordingly, on Septem- 

 ber 3, 1933, 100 marked yearling rainbow trout were set free in the 

 same section of the stream in which brook trout had been liberated 

 the previous year. 



Observations made on these fish shortly after they had been 

 liberated showed a much greater tendency to scatter than in the case 

 of the brook trout. They were also more difficult to take on fly and 

 on only 1 day during the course of the experiment was it found 

 possible to capture the desired daily quota of 10 fish. Fishing was 

 continued with varying intensity up to September 26. During this 

 period the total number of marked fish taken was only 49, and in 

 order to capture this number it was found necessary to resort to 

 bait in a number of instances. 



In general the rainbow trout reacted quite differently from the 

 brook trout in the previous experiment. Especialh^ noteworthy Avas 

 the much greater tendency to move downstream with the current. 

 For example, 59 percent of the fish recaptured were taken below the 

 pools in which they had been liberated; 29 percent from the pools 



