is of utmost importance in maintaining sport 

 fishing. Dams in the upper reaches of streams 

 and rivers particularly are a threat since they 

 flood out trout spawning areas, destroy valu- 

 able trout stream habitat and substitute ar- 

 tificial impoundments that are difficult and 

 sometimes impossible to manage as a fishery. 



Negotiations to insure the best possible 

 water conditions for fish in reservoirs and in 

 the rivers below the reservoirs must be car- 

 ried on during the planning stages long before 

 construction starts. Impoundments that will 

 result in excessive damage to fish or game 

 are opposed and consideration requested for 

 less damaging sites. Such negotiations require 

 knowhow and intensive effort. Recommenda- 

 tions for provisions involving reservoir opera- 

 tions and flow releases must be based on 

 adequate field work and careful analyses. 



A multimillion dollar highway construc- 

 tion program is in progress in Montana. Road 

 construction that results in stream straighten- 

 ing removes the meanders which are so very 

 important in providing cover and resting areas 

 for fish. Population studies on Flint Creek, 

 near Philipsburg, Montana show a 947c reduc- 

 tion in catchable size trout when the stream 

 was straightened during highway construc- 

 tion. During the biennium about 20 plan-in- 

 hand inspections were made with constructing 

 agencies in an effort to minimize this damage. 



Accumulative effects of dam building, 

 stream straightening, pollution of all kinds 

 (including silt), removing excessive amounts 

 of water from streams for irrigation, stream 

 bank trampling by livestock, and other abuses 

 are reducing trout stream habitat at an alarm- 

 ing rate. Compared to these factors, fishing 

 pressure is a minor cause of the decline of 

 fishing in Montana. 



Pollution Control 



The department pollution biologist, work- 

 ing under a cooperative agreement with the 

 State Board of Health, participated in the 

 classification of the Columbia River Drainage. 

 This classification was in relation to water 

 use by aquatic life. Under the same coopera- 

 tive agreement, biological data needed for 

 classification of the Missouri River Drainage 

 has been gathered. These data are now being 

 tabulated and summarized so that classification 



of this important river drainage can be ac- 

 complished. A comprehensive report on the 

 bacteriological, biological, chemical, and physi- 

 cal aspects of the Columbia River Drainage 

 was written during the biennium. 



Water chemical sampling is in progress on 

 the primary rivers that form the Missouri 

 River mainstem. This survey, when completed, 

 will give information on present water quality 

 in these important trout streams. This in- 

 formation will be extremely valuable in recog- 

 nizing and evaluating future changes. 



Three fish - kills were investigated and 

 abatement measures taken by State Board of 

 Health and Fish and Game personnel. Streams 

 likely to receive waste materials harmful to 

 fish and other aquatic life are under close 

 surveillance. In addition, a good deal of the 

 pollution control biologists' time has been 

 spent surveying state waters to determine the 

 effects of industrial and domestic wastes on 

 aquatic life. 



During the biennium the biological pollu- 

 tion laboratory has been modernized and is 

 now in a position to handle many of the 

 problems concerned with pollution. 



Effects of Forest Spraying With DDT on 

 Aquatic Life 



This project was partially conducted in 

 cooperation with the U. S. Forest Service to 

 gather information on the use of DDT aerial 

 sprays which might be used in current spruce 

 budworm control. During this period, investi- 

 gations were continued on areas sprayed dur- 

 ing previous years. They involved a check 

 on the recovery of fish and bottom insects 

 (fish food) in streams where mortalities oc- 

 curred as the result of DDT. A final report 

 "Effects of an Aerial Application of DDT on 

 Fish and Aquatic Insects in Montana" was 

 prepared in cooperation with the U. S. Forest 

 Service. 



In addition, an intensive study of the ef- 

 fects of DDT was carried out as a graduate 

 research problem at Montana State College. 

 It was supported in part by the Montana 

 Fish and Game Department. This investiga- 

 tion has included a controlled application of 

 DDT to a test stream and bioassay work with 

 trout exposed to and fed insects with various 

 concentrations of DDT. The field work in this 



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