INTRODUCTION 



This project is a long-term interagency cooperative study with the U. S. 

 Forest Service. The Montana Department of Fish, Wildlife and Parks (MDFOT) 

 portion of the effort will be to collect fish population data in the same areas in 

 \-iiich the Forest Service is collecting sediment data. Sediment and fish population 

 responses over a number of years and different ecological situations addressed in 

 this effort will produce better interagency confidence in land-use practices and 

 allocations. 



OBJECTIVES 



1) Compare fish population response to different levels of embeddedness on 

 12 study streams. 



2) Evaluate other habitat components that may explain variation in fish 

 populations between study streams. 



3) Identify fish population spatial distribution and migration patterns 



PROCEDURES 



Fish populations were estimated with the nark and recapture method. We used 

 Chapman's modification of the Peterson formula described by Ricker, 1975. 

 Variance estimates were made with Chapman's formula also by Ricker, 1975. Due 

 to the statistical consideration of acquiring an adequate sample size of fish 

 for good population estimates, our study sections required greater length than 

 the sediment stations selected by the Forest Service. Our sampling sections were 

 permanently marked with steel fence posts on the lower boundary of the section. 

 A narrative description of the location of the sections was prepared on most 

 of the sections and appears in the appendix. All study section lengths were 

 measured with a tape. We tagged most of the trout handled larger than 4 inches 

 total length with fingerling tags (Floy). 



Fish habitat parameters were not addressed this first season. 



RESULTS 



Fish population sampling began in August and September of 1985 with the completion 

 of field collections on 13 stream sections on 10 streams. Two stream sections on 

 Rock Creek were not completed but will be added next season, since this is the 

 first year of a long-term effort. 



In addition to the fish population estimates completed, we collected cutthroat 

 trout on some of the Bitterroot drainage streams, from sections outside our 

 population estimate sections, for westslope cutthroat genetic evaluation. The 

 report of findings appear in Appendix A-1 of this report. 



Westslope cutthroat trout dominated the fish populations in all 13 sections 

 sampled. The number of westslope cutthroat larger than 6.0 inches total length per 

 300 meters of stream length in Figure r'shows a highly variable nature of fish pop- 

 ulation density in the stream sampled. Of both concern and interest is the comparison 

 of the West Fork of Rock Creek sections with other sections, while appearing capable 

 of producing more larger fish, fail to equal some of the much smaller stream standing 

 crops. 



