elevated slightly above that expected Most of the filter-feeding organisms were the 

 caddisfly Hydropsyche sp. This finding suggests that suspended fine organic particulates 

 were plentifijl in this reach, perhaps compromising water quality to a slight degree. It also 

 correlates with the finding of slight streambank instabiUty, sub-optimal riparian zone 

 integrity, and light deposition of fine sediments noted in the habitat assessment. The 

 overall affect of these conditions on biotic health, however, appears to be very slight. 

 Eight mayfly taxa and a low biotic index value (2 36) suggest that water quality 

 perturbations do not substantially impair biotic health in this reach Excellent large-scale 

 habitat is indicated by the high number of stonefly taxa, among them were the sensitive 

 shredder Zapada columbiatKi and the perlid Doroneuria sp., which is also sensitive to 

 many types of habitat disturbance Long-lived taxa, including three different species of 

 perlid stoneflies and the caddisfly Arctopsyche grandis were abundant, indicating 

 adequate year-round streamflow and no periodic disruptive events. The presence of 9 

 caddisfly taxa and 18 "dinger" taxa suggests that the slight sediment deposition noted by 

 the field investigator does not compromise biotic health to any great extent. Predator taxa 

 were abundant and diverse, ten taxa comprised 16% of the sampled assemblage. This 

 suggests good instream habitat. Sixteen percent of the organisms sampled were 

 shredders, indicating good riparian inputs of large organic material, and stream 

 morphology and flow conditions adequate for retention of such material 



At Johnstone station, on the other hand, only 3 mayfly taxa were represented in 

 the sample, and the biotic index value (4.89) was considerably higher than expected. In 

 addition, 33% of the assemblage were midges. These findings suggest that water quality 

 impairs biotic health in this reach of Shields River Abundant filter-feeders (29°/o of the 

 assemblage) suggest that fine suspended organic material was abundant here, and may be 

 an indication of poor streambank stability and associated erosion, heavy sediment 

 deposition, and embeddedness of benthic substrates noted in the habitat assessment. No 

 sensitive taxa were present in the sample Only two predator taxa (1% of the assemblage), 

 most of them the tolerant svn^t^y Atherix sp , were collected, suggesting monotonous 

 substrates and poor instream habitat quality. Further, 4 caddisfly taxa, dominated by the 

 sediment-tolerant Hydropsyche sp , and 10 "dinger" taxa were present in the sample, 

 indicating that sediment deposition limited the diversity of benthic invertebrates here. 

 Only 20 unique ta.xa were collected A single shredder taxa was present, indicating very 

 limited riparian contribufions of large organic material. 



CONCLUSIONS 



• With the exception of a slightly elevated filter- feeder component to the 

 assemblage, the benthic invertebrates at the McCloud station indicate essentially 

 unimpaired biotic health Increased filter-feeders may indicate excessive 

 suspended fine organic particulates, which in this reach of Shields River may be a 

 consequence of some degree of streambank instability and associated erosion. 



• Both water quality perturbations and habitat degradation appear to impair biotic 

 health at the Johnstone station. Impairment was classified as "moderate", but the 

 score was very low Metric performance and taxonomic composition of the 

 assemblage suggested that water quality was impaired by nutrient and/or organic 

 enrichment. Habitat degradation appears to have resulted in heavy fine sediment 

 deposition with the resultant loss of instream habitat 



