This survey demonstrated that, while most certainly any trout 



fishing at all must be depend- 

 ent upon hatchery plantings, 

 nevertheless because of the 

 large population of rough fish 

 present such plantings would be 

 futile. As a result of the sur- 

 vey, in late summer of 1953, 

 500 pounds of a commercial 

 toxicant were introduced into 

 the stream in an experimental 

 rehabilitation project. 



In the case of Otter Creek, 

 which empties directly into Belt 

 Creek, undesirable fishes will 

 be able to move again into the 

 rehabilitation area. The plan 

 here was to stock the rehabil- 

 itated area, as has been done, 

 with brown trout while there 

 were no rough fish present. 

 Rainbow and brook trout were 

 present before. 



Percent of each group of fish re- 

 covered from sampled sections of Otter 

 Creek, Judith Basin and Cascade Coun- 

 ties, Montana, August, 1952. 



Observations will be made in subsequent years to measure the 

 rate of recontamination by rough fish if such occurs, and to deter- 

 mine the economic feasibility of this type of management against 

 the economic feasibility of continued plants of hatchery fish into 

 large populations of rough fish. 



In cooperation with the Montana State College Agricultural 

 Experiment Station an investigation was conducted in this biennium 

 in district number 1 on the relation between trout and yellow 

 perch in Thompson Lakes. Total rehabilitation of this chain of lakes 

 is not as yet economically feasible because of the combined area 

 of the lakes. The native cutthroat trout populations of the lake 

 did furnish excellent sport angling. With the introduction of yellow 

 perch into these lakes, trout fishing has all but ceased. Kokanee 

 have been planted and are furnishing the bulk of the still poor sport 

 fishery. 



It was noted in the study that during a short period in the 

 spring, the yellow perch are concentrated on the shoal areas while 

 the kokanee and cutthroat trout are in the deep waters. It was noted 

 also that partial poisoning during this period along the lake margins 

 and in the bays killed perch in large numbers at low costs without 

 killing kokanee and cutthroat trout. 



Based upon this work a further experiment has been planned 

 for execution during the summer of 1954, whereby a concentrated 

 effort will be made using fish toxicants to reduce drastically the 

 perch population in one of the lakes by partial poisoning. 



As soon as the treated area of this lake is non-toxic cutthroat 

 trout fry will be planted into the shoal areas of the lake at a 



77 — 



