tributaries of the lower drainage (Gold, Belmont and Bear Creeks), and many other 

 tributaries to the Blackfoot River. Many of these streams show mild infection levels and 

 no signs of rainbow trout declines at this time, despite higher infections in receiving 

 waters. Water temperatures are also typically much lower in forested and upper stream 

 reaches (Pierce et al. 2002) and out of the reported critical temperature range of high-risk 

 waters (Vincent 2002). As a result, the risk of exposure is variable, but in general should 

 increase in the downstream direction. These downstream-infected areas often overlap 

 with rainbow and brown trout spawning areas (Pierce et al. 2002, this report Study area 

 maps. Figure 8). 



One exception to habitats where native fish appear somewhat isolated from the 

 disease is lower Chamberlain Creek. Lower Chamberlain Creek supports concentrated 

 WSCT spawning and high juvenile densities (Pierce et al. 1997; Schmetterling 2001) in 

 lower stream reaches in an overlapping area of high whirling disease infection (Table 1 7). 

 Infection levels in July have reached mean grades of 3.9, a grade considered to cause 

 population declines in exposed fish (Vincent 2002). WSCT numbers have been 

 declining beginning in 2000; however, the confounding drought conditions limit 

 interpretation of the disease's true effects. Fortunately, the disease currently appears 

 localized at the lower-most portion of Chamberlain Creek, largely downstream of WSCT 

 spawning areas. 



WSCT telemetry studies conducted in the Blackfoot River have identified several 

 important spawning tributaries (Axrastra, Belmont, Chamberlain, Copper, Gold, Monture, 

 Sauerkraut, upper Willow and Wales Creeks, and the North Fork Blackfoot River). Four 

 of these (Copper Creek, Sauerkraut Creek, upper Willow and Wales Creeks) have not 

 been tested for the presence of whirling disease. The remaining six streams all tested 

 positive with mean grade infections ranging from 0.12 to 4.5 (Table 17). Although 

 whirling disease is present in the lower segments of these streams, known WSCT 

 spawning typically occurs at elevations above the disease, hi many cases, this upstream 

 spawning appears to segregate critical early life stages from parasite exposure. In 

 addition, telemetry investigations and monitoring of primary bull trout spawning sites 

 show these areas to be currently free of the parasite, despite infected downstream waters. 



The effect of habitat restoration on whirling disease severity is being investigated 

 in the Blackfoot watershed. Our objective is to determine if restoring an infected system 

 (i.e. reducing favorable worm habitat by regaining flushing flows and reducing sediment 

 input through stabilizing banks) will moderate the disease. The premise behind this idea 

 is a result of several ecological risk factors being hypothesized to influence whirling 

 disease severity. These factors include: high productivity, lack of flushing flows, low 

 gradient, human altered or enriched habitats that amplify the density of T. tubifex, and the 

 presence of brown trout that can act as a reservoir for the disease (Modin 1998; 

 Mc Williams 1999; Zendt and Bergersen 2000). All of these factors, including high levels 

 of whirling disease were present in KJeinschmidt Creek, a stream that was restored in 

 2001. Through this restoration work width to depth ratios decreased, velocities increased, 

 stream banks were stabilized and water temperatures were moderated. WTiirling disease 

 has been monitored in this stream prior to, during, and after restoration and a decrease in 

 infection has not yet been detected. Initially, whirling disease was detected at a mean 

 grade of 2.8 in July of 1998. Results from cage studies in 2003, two years post project, 



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