2 



Urban and non-urban stream did not differ significantly with respect 

 to water velocity, nitrate content, or amount of cover that was in the form 

 of pools or water-surface trubulence. 



Trout abundance expressed as kilograms per hectare was generally below 

 the level indicated as potential according to the Wyoming Habitat Quality 

 Index (HQI) in both urban and non-urban areas. This, as well as poor 

 coorelation betwen HQI values and measured trout abundance may have been 

 due to various possible circumstances: (1) suppression of trout abundance 

 by some unmeasured factor or factors, such as angling, pollution or 

 artificial diminution of streamflow discharge, (2) inapplicability of the 

 HQI method to the kinds of stream in the study, (3) error in estimation 

 of habitat and/or trout population variables, or (4) inappropriateness of 

 biomass per unit stream surface area as a measure of trout abundance. 



A second type of regression analysis of association between trout 

 abundance and habitat variables indicated that the lumping of all cover 

 types (pool, turbulence and overhead) which is involved in the HQI method 

 may have been a major source of poor predictiveness. Multiple correlation 

 was far higher when overhead cover and pool-and-turbulence cover were 

 treated as separate variables. This analysis indicated that 71% of 

 variation in number of over-20-cm trout/km was attributable to the 

 combined variation in the following habitat factors in this order of 

 importance: (1) mean water velocity in stream reach, (2) ratio of late 

 summer streamflow discharge to mean annual discharge, (3) amount of 

 nolid overhead cover, ('I) maximum summer water temperature, and C?) 

 amount of aquatic vegetation in the stream. 



