328 REPORT OF THE SECRETARY OF THE INTERIOR 
Forest Service has complete control over all streams, management 
programs worked out by the Bureau of Fisheries have been in opera- 
tion. Good results were already apparent in 1939, and during this 
and the 1940 season it was possible to accommodate more anglers and 
to permit a longer open season than in previous years. Management 
studies in the intermountain region have been concerned chiefly with 
the fisheries problems of Fish Lake, Utah, and of Bear Lake, which 
is situated almost equally in Utah and Idaho. In California, while 
experiments on the survival of hatchery trout after planting are still 
under way, the attention of the staff has been given principally to the 
problem of devising a plan for salvaging salmon whose migration 
will be blocked by the Shasta Dam. This dam will be approximately 
560 feet high and will cut off all salmon spawning areas above it in 
the Sacramento, Pit, and McCloud Rivers and their tributaries. The 
value of these salmon runs has been calculated at $95,000 annually 
in returns to commercial fishermen. After surveys of potential 
spawning areas below the dam and of possible sites for trapping the 
runs for transfer to such areas, a preliminary report embodying 
recommendations for the salvage operations was issued in June 1940. 
Water quality investigations —One of the major activities of the 
aquatic physiologists during the past year was a study of the effects 
of various components of larvacides and herbicides on fresh-water 
fishes and their associated aquatic food organisms. These studies 
have now provided evidence that in waters treated with even small 
quantities of arsenicals and several other materials commonly used 
as mosquito larvacides, there is impairment of the growth and nutri- 
tion of fishes. 
Application of physiological, biochemical, and metabolic methods 
to the study of fishes from irrigation waters has demonstrated that 
the physiological condition and reproductive capacity of such fish is 
often below par, a condition traceable to the concentrations of mineral 
salts discovered in many return irrigation waters. The same methods 
of study applied to fishes from waters polluted with mine wastes 
revealed that chronic injuries result from much higher dilutions of the | 
wastes than heretofore have been recognized. 
During the summer of 1939 intensive studies of stream pollution 
were made along the Atlantic seaboard and throughout the greater 
part of western United States, resulting in the collection of much 
new information on the nature and effects of polluted waters. 
Studies of impounded waters were continued at Elephant Butte 
Reservoir in cooperation with the Reclamation Service and the 
National Research Council, and at Lake Mead in cooperation with the 
same agencies and the National Park Service. 
