Blackfoot River into a lower and upper reach based on the physical characteristics of 

 nearby tributaries. The lower reach extends from the mouth of the Blackfoot River 

 upstream 34.7 river miles to the mouth of the Clearwater River. For this reach, spawning 

 tributaries have higher gradients, lower summer temperatures and currently support 

 generally lower WD infections (this report). The upper reach extends from the 

 confluence of the Clearwater River 19.4 river miles upstream to the confluence of the 

 North Fork. For this reach, spawning streams are lower gradient, support warmer 

 summer water temperatures, higher sediment levels and higher WD infections (this 

 report). -r ,. 



Methods 



Twenty-seven RBT ( 1 in the lower reach and 1 7 in the upper reach) were captured 

 and implanted with radio (Lx)tek) transmitters on March 8, 2004 and between February 28 

 and March 8, 2005. As a pilot project for the larger 2005-06 study, the 2004 fish 

 involved seven RBT in the upper reach. Transmitters for these fish had only an estimated 

 ~1 00-day battery-life. For the 2005 RBT, we implanted radios in 20 adult fish with ten 

 transmitters in each of the two reaches. We selected fish that possessed the 

 morphological features of adult female in pre-spawning condition and avoided fish that 

 exhibited obvious westslope cutthroat trout (O. Clarki lewisi) characteristics. 

 Transmitters were evenly distributed throughout reach one, and concentrated near the 

 center of reach two due to limited access. Fish captures were made in suspected 

 wintering pools, prior to spawning migrations using a boom-mounted electrofishing drift 

 boat. 



We followed surgery methods described by Swanberg (1997) and Schmetterling 

 (2001). Transmitters weighed 7.7 grams and did not exceed 2% of fish weight as 

 previously suggested (Winter 1 996). Transmitter life for the 2005 fish was estimated at 

 450 days. Incisions were closed with Reflex-One 35W surgical staples (Swanberg et al. 

 1999). Following surgery, the fish were held in a live car in the river until ftilly 

 recovered and then released at or near capture locations. Each fransmitter emits an 

 individual coded signal. 



Fish locations were determined from the ground, using either an omni-directional 

 whip antenna mounted on a truck or a hand held three-element Yagi antenna when 

 walking. We located fish weekly prior to migrations, daily during migrafions and 

 spawning, once per week following spawning and once per month during the late 

 summer, fall and winter due to reduced movements. Fish were categorized as spawning 

 (entered a tributary) or non-spawning (did not enter tributary). Fish were assumed to 

 have spawned if they ascended a tributary during the spawning period. The mean date 

 between two contacts surrounding an event, such as a migration start, was used to 

 estimate the date of an event (Schmetterling 2001). 



Thermographs (Tidbit sensors) were placed in both reaches of the Blackfoot River 

 and (Hobo sensors) and at the mouth of all tributaries to evaluate the effect of 

 temperature on the onset of migration and spawning. These thermographs recorded 

 temperature every 48 minutes (Tidbit sensors) in the mainstem and 72 minutes (Hobo 

 sensors) in tributaries. All temperature statistics were obtained from maximum daily 

 temperatures. Blackfoot River daily discharge data were obtained from U.S. Geological 



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