Final Report pdf file

 Abstract

Benthic macroinvertebrate data from reaches of the North Fork Feather River (NFFR), affected and unaffected by monthly pulsed recreation streamflow releases during 2004, were compared using a before-after-control-impact (BACI) design. Macroinvertebrate populations in the treated and control reaches were sampled using representative artificial substrates (rock basket samplers) and standard kick sampling techniques. Macroinvertebrate data were described using the recently developed hydropower multi-metric index (Hydro-MMI), which was designed to be sensitive to the effects of hydropower operations. Analysis of variance (ANOVA) was used to test for a pulsed-flow effect. The control-to-treated difference in Hydro-MMI was significantly different from pre-flow to post-flow (p < 0.10). Among basket-sample data, seasonal trends between these two reaches were generally similar; however, kick-sample data suggest a seasonal pattern of increasing richness and abundance in the control reach that was not observed in the treated reach.

 Comparisons of the basket and kick sampling techniques demonstrated that basket samplers selected for a subset of the benthic community dominated by filter-feeding organisms such as net-spinning caddisflies. These organisms appeared able to quickly colonize and capitalize on free interstitial spaces provided in basket samplers. Kick samples provided a better representation of the overall benthic community. Differences in the composition of the two sample types suggest that seasonal trends among basket-sample data primarily followed natural seasonal patterns for the filter-feeder-dominated community that developed in basket samplers, which may be less sensitive to flow-related changes than the larger benthic community.

Installation of samplers at the control site (May 2004)	Installation of samplers at the treatment site (May 2004)
Retrieval of samplers (June 2004)	GANDA biologist Ian Chan processing a field sample

Photo credit: Garcia and Associates
(Please request permission from ichan@garciaandassociates.com for use of pictures)