NORTHWEST FISHERIES DISTRICT 



During the biennium 13 streams and 35 lakes 

 were surveyed in the Northwest Montana Fisheries 

 District. The purpose of these studies is to determine 

 the physical, chemical, and biological qualities of 

 our better sport fishing waters. These surveys are the 

 basis for management recommendations and re- 

 habilitation projects. They also provide the basis for 

 amending the hatchery planting program to make 

 optimum use of hatchery fish. Species presently used 

 in managing the northwest district waters are cut- 

 throat, rainbow, eastern brook, golden trout, and 

 largemouth bass. 



The Flathead River and its tributary streams 

 above Flathead Lake are providing good to excellent 

 cutthroat trout fishing. A study on cutthroat was 

 designed to gain information on the extent of their 

 spawning areas, the time of spawning, the distance 

 traveled, and the numbers of young fish returning to 

 Flathead Lake. 



To date, 1,175 west-slope cutthroat trout and 216 

 Dolly Varden have been tagged and released in the 

 171 miles of the Flathead River system. Tag returns 

 on these fish show considerable movement during 

 their life cycles to and from spawning streams. 

 Young tagged fish move downstream in the fall. 

 Downstream trips of over 40 miles in less than one 

 week are not unusual.The majority of these fish 

 range in size from 7 to 10 inches long and furnish 

 the recruitment to the Flathead Lake fishery. Spring, 

 upstream movements, tend to be slower and are 

 regulated by run-off and water flows in the river 

 system. These fish are the larger mature fish ranging 

 from 12 to 17 inches long. The information gained 

 in this study further exemplifies the importance of 

 secondary spawning tributaries. Maintaining pas- 

 sageways to these streams for spawning fish and 

 downstream recruitment is an important phase in 

 the management of the Flathead Lake fishery. 



During this biennium twelve lakes in the district 

 were rehabilitated through the use of toxaphene and 

 emulsifiable rotenone. These treated lakes have a 

 combined surface acreage of 806 acres and range 

 in depth from shallows of 1 to 2 feet to a maximum 

 of 160 feet. 



WESTERN FISHERIES DISTRICT 



Two long-range creel census jobs, lake rehabili- 

 tation and experimental work with mechanical aera- 

 tion systems, highlighted fishery work in the western 

 district during the biennium. However, general sur- 

 vey work continued to be the major project activity 

 and covered 26 lakes and 38 streams. Fifty-three of 

 these were initial surveys. Their purpose was for 



continued cataloging of waters to provide a basis 

 for future management. The remainder (on 1 1 waters) 

 were re-surveys to evaluate the effect of experimental 

 management practices, or some new land or water 

 use project. 



The Georgetown Lake creel census was continued 

 during the winter of 1960-61 and summer of 1961. 

 The purpose of this study, which began in 1958, is 

 to provide harvest and fishing pressure information 

 necessary for the best management of this popular 

 fishing lake. Although this census, which is made at 

 two-year intervals, has only completed its second 

 year, it has already shown that Georgetown Lake 

 can be open to fishing for one more month per year 

 with little if any loss in fishing quality. 



The section of the Clark Fork River most severely 

 affected by the 1960 pollution problem was closed 

 to angling in 1960 and 1961. The river was sampled 

 both years to check its damage and recovery. Game 

 fish, which were very scarce in 1960, had increased 

 over five times by 1961 and the river was opened to 

 fishing with the general season in 1962. 



A population study was begun on three western 

 Montana water-supply streams which have been 

 closed to fishing for many years. The objective of 

 this job is to determine normal ups and downs of 

 fish in unfished streams and to record the effect of 

 fishing pressure on virgin streams. One stream was 

 opened to fishing in 1962. The study will continue 

 for several years and will furnish needed information 

 on the management of our relatively sterile, west- 

 slope, cutthroat streams. 



Winterkill of fish occurs in ice-covered lakes when 

 oxygen dissolved in the water is used up. Two me- 

 chanical aeration systems for preventing winterkill 

 have been tested in western district lakes during the 

 biennium. Considerable work remains to be done 

 on the chemical, biological and thermal effects of 

 aerators and on the safety of their installations. It 

 may be that winterkill can never be entirely pre- 

 vented, but it seems likely, judging from our work 

 so far, that both its frequency and severity can be 

 reduced by the proper use of aeration systems in 

 certain lakes. Experimental work on these aerators 

 and evaluation of their effects will continue for 

 several years. 



One 300-foot section of Flint Creek, near Philips- 

 burg, has been sampled five times since 1955. This 

 section was straightened and cleared by highway 

 construction in late 1956 and early 1957. The 1956 

 sampling was done before, and the 1957 sampling 

 after the construction job. Numbers of trout, six inches 



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