The standing crop of brook trout in the study section was estimated by 

 using a mark -re capture method (Table 15). The section supported approximately 

 265 brook trout representing a biomass of 24 pounds. Catchable fish (6 inches 

 and larger) composed 38 percent of the brook trout populations. Brook trout 

 condition (length to weight ratio) was excellent and above average for Mount 

 Haggin streams and upper Big Hole River tributaries (MDFWP unpublished data). 



Table 15. Estimated standing crop of brook trout in a 1,000 foot section of 



Oregon Creek (T3N, RllW, Sec 20C) on August 5, 1980. Eighty percent 

 confidence intervals are in parentheses. 



Per 1,0 00 ft. 

 ^P^^'ies Length Group (inches) Number Pounds 



Brook Trout 3.5 _ 6.9 221 



7.0 - 11.1 44 



265(+28) 24(+3) 



The trout populations observed in the study section revealed a good fishery 

 relative to the size of Oregon Creek. Fisheries in the lower reaches of 

 the stream may be affected by habitat destruction from past placer mining 

 operations and sediment loading from a slumping hillside and subsequent 

 slumping of the roadbed of Highway 274 at the Oregon Creek road crossing. 



4. FLOW RECOMMENDATIONS 



Cross sectional data were collected in a 178 foot riffle-pool-run 

 sequence located approximately at stream mile .2 (T3N, RllW, Sec SOB). Five 

 cross sections were placed within this sequence. The WETP program was 

 calibrated to field data collected at flows of 8.9, 4.7 and 0.5 cfs. 



The relationship between wetted perimeter and discharge for a composite 

 of two riffle cross sections is shown in Figure 5. Lower and upper inflection 

 points occur at .4 and 2 cfs. Based on an evaluation of the existing 

 fishery, a flow of 1 cfs is recommended for the low flow period (July 1 - 

 April 30). Due to a lack of long term flow data, recommendations for the 

 high flow period (May 1 - June)cannot be derived for Oregon Creek. 



- 41 - 



