McNeil Core spawning site surveys in the Blackfoot River basin : ^ 



Introduction 



The reproductive success of Blackfoot River trout populations often relates to the 

 amount of "fine sediment" in spawning sites. Excessive sediment deposition can 

 effectively smother incubating eggs and entomb alevins and fi"y, the effects of which can 

 diminish recruitment to trout populations (Waters 1995; Reiser and White 1988). McNeil 

 coring is a standard method used to classify, compare, and monitor spawning substrates 

 (Lotspeich and Everest 1981, McNeil and Ahnell 1964). In western Montana, these 

 coring methods apply not only to the characterization of spawning substrates and 

 evaluations of the survival to emergence for bull trout and WSCT fiy (Weaver and Fraley 

 1993; Fraley and Weaver 1991), but also to the monitoring of sediment producing 

 activities such as road development and livestock-related streambank disturbances and 

 associated corrective measures. ■ = 



In 2004 and 

 2005 we collected m^, 



McNeil core samples at 

 29 salmonid spawning 

 sites on 22 streams 

 (Figure 55). 



The 2004 study 

 characterized substrates 

 adjacent to bull trout 

 redds in four separate 

 spawning streams and 

 compared findings to 

 comparable sites (pool 

 tail-outs) in four 

 suspected historical bull 

 trout spawning streams, 

 including three restored 

 spring creeks and one 

 basin-fed stream. Bull 

 trout spawning streams are Gold Creek, Dunham Creek, Monture Creek and Copper 

 Creek. Non-spawning streams include a section of Cottonwood Creek and three recently 

 restored spring creeks (Rock Creek, Kleinschmidt Creek and Nevada Spring Creek). Our 

 purpose was to help determine if suspected historical sites provide and environment 

 conducive to bull trout reproduction. We also compared sediment cores on Monture 

 Creek at two locations - at an unstable site upstream of an undersized bridge and below 

 the bridge in a more geomorphically stable reach (Dave Rosgen, personal 

 communication). 



The 2005 core sampling measured spawning substrates at known spawning sites 

 for fluvial salmonids including WSCT, rainbow trout and brown trout of the Blackfoot 

 River. Implications of the combined 2004-5 studies relate to the general role (and 

 existing limitations) of individual streams to spawning success of Blackfoot River fish, 

 and to: 1) ongoing whirling disease research; 2) the recovery of bull trout; 3) the 

 refinement of restoration techniques; and 4) evaluations of sediment producing land 



76 



