been getting a good look into this natural body of 

 water by means of a special boat equipped with the 

 gear necessary to probe all portions of the lake. 

 The study includes all life in the water, most 

 importantly the fish, and from the microscopic 

 free-floating plankton through the worms and 

 insects that live in the bottom mud. In Flathead 

 Lake, many fish species lead complex lives. Some 

 spend their entire lives in the lake. Others are born 

 and spend their early lives in the more than 700 

 miles of streams of the upper tributaries and come 

 down to the lake as adults, later returning to the 

 tributaries to spawn. Determination of the fish 

 distribution in the lake throughout the seasons is 

 important so that all the factors necessary for 

 perpetuation of the game species can be taken into 

 account by fisheries managers. A very modem 

 sounder that can detect fish as well as determine 

 bottom contours has produced information of 

 immediate use by anglers as well as long term 

 scientific data. Accurate forecasts can be given of 

 the most likely areas anglers will find cutthroat, 

 kokanee, Dolly Varden or lake trout at various 

 seasons. It has been discovered that Flathead has a 

 good population of lake whitefish which anglers 

 have seldom sought before. The information has 

 been determined and made available to the fishing 

 pubUc that the kokanee is ahnost uniformly spread 

 over the entire lake at depths of 50-70 feet during 

 the summer months. 



The answers which the Flathead Lake 

 investigations will provide will be the keys to 

 continued enhancement and utilization of the 

 game species which must Uve in both the lake and 

 the tributaries, especially in the light of dam 

 proposals which if built would create additional 

 barriers to spawning runs. The study may also 

 reveal that additional game fish species might be 

 introduced into Flathead which would be 

 compatible with the existing life there and broaden 

 the sport fishing base of the lake, such as the coho. 



Pollution Control 



The State Department of Health administers the 

 Montana Water Pollution Control Act. The Fish 

 and Game Department's pollution control biologist 

 is attached by cooperative agreement to the 

 Department of Health to work with water 

 pollution where fish and game resources are 

 involved. 



Considerable progress has been made in the 

 control of water pollution by industries and 

 municipalities. Sediment pollution from 

 agricultural, construction and timber harvest 

 remain a very serious problem. 



A relatively new kind of pollution, thermal pollution, is growing 

 to frightening proportions in some parts of the United States. 

 Thermal pollution results when water is taken from a river or 

 lake, used to cool generating plants or other industrial complexes 

 and is then discharged much heated back to the parent water. 



The Fish and Game Department's pollution 

 control work had two major activities during the 

 biennium. The first was working with the Water 

 Pollution Control Council in the reclassification of 

 Montana waters and establishment of water quality 

 criteria to insure that the adopted criteria and 

 standards would be adequate to preserve fish and 

 wildlife values. Secondly, the pollution of the 

 Clark Fork River required a major effort in 

 monitoring water quality and associated 

 investigations. 



Fort Peck Commercial Fisheries Investigations 



A commercial fishery investigation of Fort Peck 

 Reservoir was started during the biennium. Passage 

 of the Commercial Fisheries and Development Act 

 of 1964 (PubUc Law 88-309) allowed partial 

 fundmg of this work by the U.S. Bureau of 

 Commercial Fisheries. A 35-foot work boat, 

 suitable for all weather operation on Montana's 

 largest reservoir, was constructed and two 

 permanent employees have been assigned to the 

 investigation. 



Goldeye, one of the most valuable commercial 

 species in the reservoir, but quite undesirable to 

 Montana anglers, had been passed up by 

 commercial fishermen in the past because they 

 were not able to capture these fish without also 

 taking large numbers of game species. Thus, the 

 first objective of the study was to find a way to 

 take goldeye selectively. A technique was 

 developed, using floating gill nets, fished away 

 from shallow areas, that resulted in a catch over a 

 six-months period that was 99.95 percent goldeye. 

 With this technique, plus promotion by local 

 business groups, a commercial fisi\ery for goldeye 

 was begun in 1967. About 50,000 pounds of Fort 

 Peck goldeye were nuirkctcd in Winnipeg (North 



