Beschta 1 982). When these fines exceed 20%, significant mortality of embryos can be 

 expected (Waters 1995). Results of the 2005 study show only two streams (Kleinschmidt 

 Creek and Elk Creek) exceed this 20% value. Both streams are water quality (including 

 sediment) impaired (TMDL 303(d)) due in part to riparian (agricultural) degradation 

 (Blackfoot Challenge 2005). Fine (soft) sediment (and organics) has also been positively 

 correlated with the abundance of T. tubifex - an obligate host to the parasite {Myxobolus 

 cerebralis) that causes whirling disease in salmonids (Granath and Gilbert 2002). 

 Corresponding with environments conducive to the input and accumulation of fine 

 sediment, both streams are also highly WD infected {this report, Table 6). 



The percentage of fine sediments (<6.35 mm) has been correlated with the 

 survival of bull trout and WSCT at the time of emergence (Weaver and Fraley 1991; 

 Fraley and Weaver 1993). The percentage of fine sediment in bull trout spawning sites 

 ranged fi-om 26.6 to 32.5, correlating to a range of survival of between 33 and 38%. This 

 percentage of fine sediment appears high, but also approximates the range of "natural" 

 levels in spawning riffles of the Blackfoot (USFS unpublished data, Kramer and Walker 

 1992). The percentage of fine sediment for nine WSCT spawning sites ranged fi-om 20.1 

 - 49.2%, correlating to a range of survival of 7 - 45%. The WSCT spawning stream with 

 the lowest predicted survival is lower Wasson Creek. This stream is currently 

 undergoing restoration and grazing-related changes that when completed should 

 substantially improve survival. 



Fredle index and geometric mean, both central tendency measures of predicting 

 embryo survival, are also accepted measures of spawning site suitability (Waters 1995, 

 Young et al. 1991). Both show positive relationships between size and embryo survival. 

 Based on these general relationships, a plot of central tendency spawning site "quality" is 

 presented graphically in Figure 56. 



Many spring creeks of the Blackfoot Valley historically supported bull trout 

 populations; however, whether these spring creeks actually supported bull trout 

 reproduction is unclear. Recent sampling by FWP has recorded the incremental 

 expansion of bull trout back into several restored streams, including spring creeks, 

 however bull trout reproduction has not been documented to date in any of these areas. 

 Larger spring creeks in particular appear to have some of the site characteristics 

 necessary for successfiil bull trout reproduction including groundwater upwelling. 

 Despite certain similarities, sediment coring found significantly higher levels of fine 

 sediment (<6.35) in two of three restored spring creeks compared to the bull trout 

 spawning streams. Other disparities involve the broader physiographic and 

 morphological settings in which existing bull trout spawning areas are found (i.e. 3"* 

 order basin-fed glacial trough valleys) in the Blackfoot Watershed {this report). In 

 addition these restored streams all exceed 30% fines (<6.35mm) - a level above which 

 survival to emergence rapidly declines (Shepard et al. 1984). Based on survival to 

 emergence equations for bull trout (Fraley and Weaver 1991), predictions of survival are 

 notably lower (range 1 1 -25%) for the restored spring creeks compared to the four bull 

 trout spawning areas (range 33-38%). At the Cottonwood Creek site, the high level of 

 fine sediment, a partial result of excessive livestock streambank damage, confounded our 

 ability to compare and interpret survey results at this site. 



It appears unlikely that levels of fines in these and other similar spring creeks will 

 decline due to low energy and low channel gradients characteristic of spring creeks. 



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