that owns and operates the Noxon Rapids 

 Plant. 



A pre-impoundment survey indicated that 

 the section of the Clark Fork River to be 

 inundated by the Noxon Rapids Dam con- 

 tained large numbers of squawfish, chubs and 

 suckers. These fish would provide brood stock 

 that would rapidly saturate the new reservoir 

 with undesirable fish. Therefore, in Septem- 

 ber, 1958, toxicants were introduced into this 

 section of the Clark Fork River to reduce 

 rought fish to the lowest possible number. It 

 would have been desirable to eliminate these 

 fish from the entire drainage; however, they 

 are generally distributed throughout the Clark 

 Fork and Flathead drainages and chemical re- 

 habilitation on that scale could not be under- 

 taken. Data collected after treatment and dur- 

 ing the 1959 season indicate that mature rough 

 fish were reduced to a very low level and 

 that reproduction, especially by squawfish and 

 chubs, was relatively low during the first year 

 of impoundment. Fingerling rainbow trout 

 planted in September, 1958 showed good sur- 

 vival and growth rates and were providing 

 excellent fishing one year later. Annual plants 

 of fingerling rainbow have been made since 

 1958. Continued study on this reservoir will 

 indicate the value of partial rehabilitation in 

 extending the period of good fishing in large 

 reservoirs. 



Information is also being gathered from 

 Cabinet Gorge Reservoir on the Clark Fork 

 River and from Hungry Horse Reservoir on 

 the South Fork of the Flathead River. These 

 reservoirs are approximately the same age 

 but represent different habitat types that are 

 reflected in their fish populations. All game 

 species combined made up less than 10 per 

 cent of the population prior to recent intro- 

 ductions of hatchery fish. Hungry Horse sup- 

 ports many Dolly Varden, cutthroat trout and 

 mountain whitefish, all of which are main- 

 tained through natural reproduction. There is 

 some indication that rough fish may still be 

 increasing in Hungry Horse Reservoir so the 

 ratio of game to rough fish may change in 

 the future. 



Several more hydro-electric or multi-pur- 

 pose projects have been proposed on rivers of 

 this area. The information gained from this 

 study will be used in management of existing 



reservoirs and will also be useful in formulat- 

 ing management plans for future hydro-electric 

 or multi-purpose projects in Western Montana. 



Test Stream 



A test area on Flint Creek in Granite 

 County, Montana has been used continuously 

 since 1954 to study certain aspects of trout 

 survival. In 1958, tests were concluded. It 

 was learned that the ability of hatchery rain- 

 bow trout to survive correlated directly with 

 quality of diet fed at the hatchery. This has 

 been the most important factor affecting 

 survival of catchable-sized hatchery trout in 

 Flint Creek. Competition with resident wild 

 trout for food and space has also had a limit- 

 ing effect on hatchery trout survival. Typically 

 about two-thirds of the catchable wild trout 

 survive for a one-year period while about one- 

 half of the planted hatchery trout survive the 

 same period. 



In 1959, a comparison of survival of Lewis- 

 town and Bluewater hatchery trout was com- 

 pleted. Despite vastly different mineral quali- 

 ties of water at these two hatcheries, there 

 was virtually no difference in survival of their 

 trout. 



Presently, measurements of the natural pro- 

 duction of catchable-size wild trout without 

 hatchery plantings are nearly complete. This 

 and other information from the Flint Creek 

 studies will point the way to better regulation 

 of trout harvests and more efficient use of the 

 expensive catchable-size hatchery fish. 



Hatchery Biologist Activities 



A detailed analysis of the cost of rearing 

 and planting hatchery trout was completed 

 during the biennium. The report appeared in 

 the April, 1960 Progressive Fish - Culturist 

 (published by U. S. Fish and Wildlife Service I. 

 It particularly concerned cost in relation to 

 size of fish. Total costs ranged from only 

 3 lOths cent per fish for one-inch fry up to 

 64 cents per fish for ten-inch trout. "Produc- 

 tion costs" which include only those hatchery 

 expenditures directly concerned with feeding 

 and handling the fish were about one-hall' of 

 total costs and compared very favorably with 

 cost data released from other states and Fed- 

 eral hatcheries. Fish managers are finding this 

 cost data useful in determining the most eco- 



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