Fisheries Habitat and Fish Populations 



Bull trout redds are much larger than the 

 cutthroat trout redds we sampled. The greater 

 area of disturbed gravel makes it more difficult 

 to obtain egg pocket samples. We feel this effort 

 should continue to further refine embryo sur- 

 vival modeling. Data from even a small number 

 of bull trout egg pockets would help our predic- 

 tive abiUty. 



Streambed Coring 



The size range of streambed material is 

 indicative of spawning and incubation habitat 

 quality. Most research shows negative relation- 

 ships between fine sediment and embryo sur- 

 vival to emergence (Chapman 1988). We used 

 a McNeil Corer (McNeil and Ahnell 1964) to 

 collect streambed samples which were dried 

 and sieve analyzed to determine the particle 

 size composition. As the percentage of fine 

 material increased, habitat quality decreased. 



Median percentages (12 per site) of stream- 

 bed material less than 6.35 mm ranged from 

 24.8 percent in Chepat Creek to 50.3 percent in 

 Jim Creek. The values at our 29 sampling sites 

 averaged 36.3 percent. The maximum variabil- 

 ity observed within individual streams was about 

 20 percentage units. To obtain an indication of 

 natural sediment levels, we averaged the McNeil 

 core sampling results for the nine watersheds 

 where the Sequoia index (Potts and Mclnemey 

 1990) was 0.00, indicating no disturbance. This 

 calculation resulted in an average value of 3 1 .7 

 percent. Of these nine watersheds, we know of 

 significant natural sediment sources with high 

 levels of channel storage above the study areas 

 at two sites — Elk Creek and Lion Creek. The 

 Sequoia Model does not consider natural sedi- 

 ment sources or other natural phenomena which 

 may alter streambed conditions. Eliminating 

 these two sites from calculations of the average 

 condition in "undisturbed" watershed results in 

 a value of 29.8 percent. 



Researchers have collected McNeil core 

 samples in selected spawning areas annually 

 during the past ten years. This period of record 

 gives an idea of how spawning area gravel 

 composition changes from year to year. The 

 average annual change in the median percent- 

 age (n = 12) of material smaller than 6.35 mm 

 in samples from Big, Coal, and Whale Creeks 

 has been 4.8 percentage units; changes ranged 

 from 0. 1 to 10.7 percentage units. These drain- 

 ages are mainly roaded timber lands. The aver- 

 age annual change in the Trail Creek samples 

 during this same ten year period was 2.1 per- 

 centage units (range = 0.2 to 5.2). The Trail 

 Creek spawning area is not subject to the ground- 

 disturbing activities in the drainage above, which 

 are occurring in Big, Coal, and Whale Creeks. 

 The average annual change observed in "undis- 

 turbed watersheds" (Sequoia index =0.0) where 

 we have completed five annual samplings is 3.0 

 percentage units (range = 0.4 to 5.5). 



We believe McNeil core sampling is reflec- 

 tive of streambed conditions in the specific 

 sampling sites. Once one year of information 

 exists, annual sampling provides an adequate 

 monitoring tool for detecting changes in stream- 

 bed composition. However, more cost efficient 

 methods would allow us to increase the level of 

 this activity basin- wide. 



Whitlock-Vibert Boxes 



As an attempt to validate a more cost effi- 

 cient method of monitoring streambed compo- 

 sition, field crews planted a total of 380 Whit- 

 lock- Vibert (W- V) boxes during the study. Other 

 researchers have reported good results in sub- 

 stituting these slotted, plastic boxes for McNeil 

 core sampling (Reiser and others 1987, Wesche 

 and others 1989). We recovered 182, for a 

 recovery rate of 48 percent. Other researchers 

 reported a 58 percent recovery rate for boxes in 

 a similar field test (Reiser and others 1987). 



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Flathead Basin Cooperative Program Final Report 



