BUREAU OF FISHERIES 159 
Feeding experiments with fingerling, yearling, and adult trout 
were carried out at the Leetown, W. Va., and Pittsford, Vt., stations 
to determine the effect on growth, mortality, and egg production of 
dry meals fed at different levels and in different combinations. One 
of the most striking results was the marked increase in growth fol- 
lowing the addition of cod liver oil to a diet composed of sheep liver 
and whitefish meal. Experiments with brood fish showed consider- 
able variation in the hatchability of eggs from fish on different diets. 
During the year a regional biologist was appointed to resume fish 
management work in the Intermountain Region. In this area fishing 
intensity 1s increasing rapidly and many of the streams are unable 
to maintain a sufficient fish population to meet demands. In addition 
to overfishing, adverse changes in the streams and lakes are im- 
portant factors in the general decline. Among such changes might 
be cited silting resulting from overgrazing, hydroelectric and irriga- 
tion projects that interfere with normal migrations, and fluctu- 
ations of water level in artificial lakes. Management plans have 
been worked out for several waters showing possibilities of early 
improvement of fishery resources. 
The staff of the California trout investigations has been engaged 
in determining the number of salmon and the extent of spawning 
streams that will be blocked by the completion of the Shasta Dam 
on the Sacramento River. The estimates of the 1938 fall run com- 
bined with the counts of the 1939 spring run fish indicate that ap- 
proximately 25,000 salmon a year will ultimately have to be handled 
im the salvage operations. Pending the completion of engineering 
surveys to determine the feasibility of certain alternative features 
of the plan, a tentative program has been drafted which calls for a 
combination of artificial propagation and provision of areas for 
natural spawning below the dam. 
Field work in bass streams was designed to measure the extent 
and efficiency of natural propagation and the effect of intensive 
fishing on the bass population. An important result of these studies 
was the finding that even in heavily fished waters there is little 
danger of serious depletion of bass if adequate spawning facilities 
are available. However, intensive fishing frequently leaves excessive 
numbers of small bass, with consequent reduction in the abundance 
of forage fishes. It is apparent that the remedy is to build up the 
food supply and that stocking with young will only serve to intensify 
the unbalanced condition. Programs for the effective management 
of bass in ponds and lakes are being developed in Florida. 
Facilities for the experimental study of fish diseases were greatly 
increased during the year with the enlargement of the field labora- 
tory at the Quilcene, Wash., hatchery, and the provision of a second 
experimental laboratory through the cooperation of the University 
of Washington. Studies of various disinfectants used in the pre- 
vention and treatment of disease were continued to determine the 
maximum nontoxic concentrations that the fish could withstand. 
Studies of common bass parasites, believed to be an important factor 
in the mortality of the young, were carried on at Leetown, W. Va. 
The Disease Service continued to aid Federal, State, and private fish- 
culturists in the diagnosis of hatchery disease. 
