fishing on Tiber Reservoir has been excellent. 

 A study is being continued so the effective life 

 of the Marias rehabilitation project can be de- 

 termined. We must determine on the basis of 

 fishing days provided, whether or not we are 

 justified in treating a lake or a drainage that 

 will be recontaminated in five or ten years. 



A recent innovation in rehabilitation work 

 is the use of fish barriers — low dams creat- 

 ing falls — to divide a drainage into smaller 

 management units. This permits progressive 

 rehabilitation downstream from the headwaters 

 without danger of rough fish re-invading from 

 below. The smaller management units can be 

 more thoroughly treated with chemicals and 

 managed individually. Late in 1957 a fish bar- 

 rier was constructed just below the outlet of 

 Rainy Lake in the Clearwater River Drain- 

 age. This is the first such fish barrier used in 

 Montana. 



Evaluating Hatchery Fish 



The fish hatcheiy is the most expensive 

 tool of fish management. During the biennium 

 over half the fisheries dollar was spent on 

 raising and planting trout. It is imperative 

 that we learn to use these fish so they will do 

 the most good. It must be realized that where 

 the habitat is suitable fish populations can 

 maintain themselves. In fact, the bulk of the 

 fish caught in Montana today are wild fish. 



In using hatchery fish, then, the actual 

 need, suitabihty of the habitat and return to 

 the creel must be considered. This requires 

 continuous study. For example, a three-year 

 study on six lakes in the Clearwater Drainage, 

 completed during the biennium, was used to 

 evaluate the different types of cutthroat trout 

 planting, which were in use on these waters. 

 It disclosed that even the heaviest type of cut- 

 throat planting that we could afford was 

 ineffective in increasing the numbers of cut- 

 throat trout in these lakes. For practical pur- 

 poses, every fish caught was a naturally 

 spawned fish. As a result all the planting has 

 been stopped. This represents a yearly saving 

 of over 750,000 cutthroat trout, both fry and 

 fingerlings. 



Consequently a new management plan 

 was inaugurated on the Clearwater Drainage 

 with the construction of the fish barrier below 

 the outlet of Rainy Lake. The three lakes and 

 the complex of streams upstream from the bar- 



Pictured he 

 planting. 



type of tank used for aerial fish 



rier are scheduled to be rehabilitated in the 

 fall of 1958 and replanted with rainbow trout 

 the following spring or summer. If this proves 

 successful, additional barriers will be built 

 downstream allowing the entire drainage to 

 be rehabilitated as described in the section 

 "Lake and Stream Rehabilitation." 



Two other studies during the biennium 

 were on Flint Creek, the department's test 

 stream near Philipsburg, and Smith Lake rear- 

 ing pond near Whitefish. It was demonstrated 

 on these waters that each stream and lake has 

 a carrying capacity in pounds of fish regard- 

 less of numbers. For Flint Creek (when the 

 flow was maintained at no less than 8 cubic 

 feet per second) this was 210 pounds per sur- 

 face acre and for Smith Lake Rearing Pond, 

 33 pounds per surface acre. Planting in excess 

 of the carrying capacity resulted in slower 

 growth, skinny fish, lower overwinter survival, 

 and only temporary surpluses. It was also 

 found on the test stream that transporting fish 

 longer than six hours in certain fish tanks 

 affected their survival. In still another test, 

 fish raised on one diet survived twice as well 

 as fish on another diet. Such studies are con- 

 tinuing and promise much needed information 

 on hatchery techniques, planting rates, and 

 survival of hatchery fish. 



Pollution Control 



Starting in 1957, a department fishery biol- 

 ogist was assigned full time to work in liaison 

 with the Stats Board of Health and Pollution 

 Council on pollution control and abatement in 

 relation to fish and wildhfe. Much of the initial 

 work will be classification of Montana streams 

 as to use. These uses are drinking water, rec- 



29 



