15 



Yaak drainage; two sites on the West Fork of the Yaak River and one site directly below 

 Yaak Falls on die main Yaak River. 



For die most part, sculpins species were allopatric throughout the study area. 

 However, it appeared that sculpins existed sympatrically at six study sites. Each of these 

 six sites involved slimy sculpins possibly in sympatry with either torrent or shorthead 

 sculpins. 



Slimy and torrent sculpin species were found together at two sites on tributaries of the 

 Kootenai River below Libby Dam. Generally, torrent and slimy sculpins were separated 

 longitudinally in the same tributary streams of the lower Kootenai River. Torrent sculpins 

 typically were found at sites in the lower end of tributary streams in close proximity to the 

 Kootenai River while slimy sculpins occurred higher up in the drainage on the same 

 tributaries. The two sites, the main Yaak at Highway 2 and Quartz Creek at the River 

 Road, were located in close proximity to the main Kootenai River. 



The physical and biological components of the habitat at these two sites were 

 indistinguishable qualitatively from sites in which each species existed in allopatry. Both 

 sites were dominated by a combined rubble and boulder substrate. The stream gradient 

 was between 1 and 2 percent for both sites. Algal abundance was uncommon at the site on 

 Quartz Creek but common on the Yaak. Benthic macroinvertebrate density was low to 

 moderate on Quartz and high on the Yaak. Quartz Creek is a Uiird order stream at the River 

 Road whereas the Yaak is a sixdi order river. The variation between these two sites was 

 not unlike the variation recorded between the allopatric sites for each respective species. 

 Slimy and shorthead sculpins existed sympatrically at four sites. Three sites were 

 located in the Yaak River drainage and the fourth site was on Prospect Creek, a tributary of 

 the Clark Fork River near Thompson Falls. Specimens from these sites were all identified 

 as slimy sculpins in the field. Laboratory identification revealed shorthead sculpins within 



