decline in LWD in the downstream direction also seems to vary with increasing channel 

 size and a greater capacity of for larger stream to move material downstream. Local land 

 clearing (middle and upper reaches) has reduced stand density and LWD recruitment to 

 some degree (Marler 1997, Confluence 2003). 



Temperature monitoring found a suitable range of summer water temperatures 

 (<65 °F) for salmonids (including bull trout) downstream of Lincoln, produced by large 

 volumes of groundwater entering the river. Groundwater upwelling and spring creeks not 

 only moderate downstream summer water temperatures, but also appear to inhibit severe 

 winter ice formation for ~25 river miles below Lincoln. Below this area of groundwater 

 influence, water temperatures progressively become extreme, with large significant 

 increases in the summer and corresponding decreases in the winter. Mid-summer 

 temperatures below Nevada Creek progressively warm in excess of >75 ° F, consistently 

 higher than all other reaches of the Blackfoot River. Temperatures >65 ° F threaten 

 growth and survival of bull trout, and when >73 ° F likewise effect rainbow trout and 

 brown trout (FWP files). Degraded water quality originating in the Nevada Creek 

 watershed and impaired riparian conditions contribute to elevated temperatures and other 

 related impairments (higman and McGuire 1990; Pierce and Peters 1990; Marler and 

 Schmetterling 1999). Fish population surveys report extremely low salmonid densities in 

 the lower Nevada Creek (Pierce et al. 1997). Between Arrastra and the North Fork, 

 charmel ice formation also progressively increases in the downstream direction in core 

 winter months (Appendix I). Severe winter conditions, including extensive areas of 

 anchor ice, induce stress and reduce juvenile trout survival of in this area of the river 

 (Peters and Spoon 1989). 



In summary, factors limiting fisheries production for the mainstem Blackfoot 

 River (Lincoln and the North Fork) appear to involve: 1) naturally low flows near 

 Lincoln, and human-induced low flows near Nevada Creek; 2) high sediment loads and 

 low insect productivity (food supply) in portions of the middle and lower reaches; 3) 

 severe winter conditions in middle and lower reaches, and elevated summer water 

 temperatures in the lower reach; and 4) inadequate juvenile recruitment in both middle 

 and lower reaches. Correcting anthropogenic impairments to the mainstem (creating 

 buffer zones and managing for vegetative heath) would improve river conditions for 

 salmonids. However based on recruitment limitations, restoring tributaries (water quality 

 and juvenile production) will also likely prove necessary to substantially improve 

 populations in the mid-to-lower reaches of the study area. 



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