12 

 station. Standing crop in kilograms and numerical density of over-20-cm 

 trout were calculated on per-hectare and per-stream-kilometer bases. 



The 95% confidence intervals (Ricker, 1975: 8l) for the estimates of 

 numbers of trout over 20 cm were also calculated for each station and section 

 and converted to density. 

 Habitat Measurements 



Stream habitat attributes were measured during the low flow period of 

 September 1982 to March I983, following the prcedures described by Binns 

 (1979, 1982) for the Wyoming Habitat Quality Index. Habitat variables measured 

 or evaluated were maximum summer water temperature, stream discharge, channel 

 width, percent of eroding banks, length of thalweg, mid-channel length, amount 

 of submerged aquatic vegetation (substrate), nitrate nitrogen level, mean 

 water velocity through station, and percent cover. The cover designation 

 included any of the following features that occurred in water at least 15 cm 

 deep: undercut banks, instream and closely overhanging terrestrial vegetation, 

 instream debris (brush, logs and "snags"), pockets of surface turbulence, and 

 pools. Pools were identified as abrupt increases in water depth. The length 

 and width of these cover features were measured, summed and converted to per 

 cent of total stream surface area in the station. Subsequently, the categories 

 of pool and surface turbulence pockets were, for more detailed analyses, 

 separated from the other cover types — which could be categorized as "solid 

 overhead cover." 



Mean water velocity through station was measured by timing an injection of 

 rhodamine dye (Binns 1982). 



Nitrate nitrogen levels were measured by the ultraviolet spectrophotometric 

 method as described in Standard Methods for Examination of Water and Wastewater 



