Fisheries Habitat and Fish Populations 



tion between independent variables could cloud 

 the assessment of cause and effect. The Sequoia 

 index assumes a ten year recovery period. It 

 does not take into account older problems still 

 having a major influence on the percentage of 

 fines in spawning gravel in several watersheds. 

 Sequoia does not consider catastrophic events 

 such as fires or floods. The channel morphology 

 and percentage of fine material in several of our 

 spawning areas are still showing effects of the 

 1 964 flood. By eliminating the watersheds where 

 assumptions dealing with recovery rates and 

 natural events are not reflective, the fit im- 

 proved (r = 0.65; n = 21). 



Conclusions 



(1) Results indicated a direct linkage be- 

 tween ground-disturbing activity (Se- 

 quoia and HjOY) and a measurable 

 fisheries habitat parameter (percent- 

 age of material less than 6.35 mm) 

 which is linked to embryo survival by 

 westslope cutthroat and bull trout. 



(2) Findings also illustrated a direct link- 

 age between ground-disturbing activ- 

 ity (Sequoia and H^OY) and an index of 

 fisheries habitat (substrate score) which 

 is linked to juvenile bull trout rearing 

 potential. 



(3) Spawning area gravel composition in 

 the nine watersheds with no develop- 

 ment averaged 31.7 percent material 

 smaller than 6.35 mm. This size class 

 comprised an average of 39.0 percent 

 in the 17 watersheds where disturbed 



area exceeded one percent of the drain- 

 age. Forest management activities have 

 had a quantifiable effect on streambed 

 composition and fish populations in 

 the Flathead Basin. 



(4) Monitoring streambed composition in 

 known westslope cutthroat and bull 

 trout spawning areas can provide fish- 

 eries information useful in making land 

 management decisions. Once an initial 

 sampling is complete, McNeil coring 

 is an adequate tool for quantifying 

 streambed particle size composition in 

 spawning areas. We can detect changes 

 in gravel composition. 



(5) Monitoring streambed substrate score 

 in known bull trout rearing areas can 

 provide fisheries information useful in 

 making land management decisions. 

 Substrate scores are not adequate indi- 

 cators of rearing potential for fish spe- 

 cies other than bull trout. Behavioral 

 differences between the trout species 

 present in our study area makes use of 

 a single index impossible. 



(6) A significant relationship exists be- 

 tween substrate samples collected us- 

 ing modified Whitlock-Vibert boxes 

 and McNeil core samples taken at the 

 box planting sites. However, more work 

 is required before the W-V box tech- 

 nique can replace McNeil coring in our 

 streambed substrate monitoring pro- 

 gram. 



Page 68 



Flathead Basin Cooperative Program Final Report 



