Year of Award

2010

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Environmental Studies

Department or School/College

Environmental Studies Program

Committee Chair

Daniel Spencer

Commitee Members

Scott Woods, Vicki Watson

Keywords

fish populations, habitat quality, placer mining, stream restoration, trout habitat

Abstract

Thompson, Emily, Master of Science, July 2010 Environmental Studies The Effectiveness of Trout Habitat Restoration in Eustache Creek, a Formerly Placer-Mined Stream in Western Montana Committee Chair: Dr. Daniel Spencer Aquatic ecosystems in the western U.S. have been severely degraded over the last century by anthropogenic activities such as mining, logging and grazing. Habitat heterogeneity in streams of the western United States has been lost as a result of both in-stream activities (i.e. dredging and straightening channels) and riparian zone activities (i.e. logging and vegetation removal). A commonly stated objective of stream channel restoration projects is to restore stream habitat quality and thereby improve aquatic species habitat and ultimately increase fish populations. The Ninemile drainage of the Clark Fork River watershed was historically a thriving native Bull trout and Westslope cutthroat trout (WCT) fishery. Intensive mining and logging activities throughout the watershed have severely impaired native fish habitat and reduced fish populations. In 2006, Lolo National Forest partnered with Trout Unlimited to restore a 1.3-mile section of Eustache Creek at the headwaters of the Ninemile drainage. This study used pre- and post-restoration habitat and fish sampling data from 2005-2009 to analyze changes in habitat quality and fish abundance in three reaches of Eustache Creek. Habitat quality was assessed using six metrics: width to depth ratio, percent of pool habitat (based on site area), residual pool depth, large woody debris per 100 meters, large woody debris median diameter and percent fine sediment in pool tails. A repeated measures ANOVA model was used to detect significant increases in habitat quality and fish populations over the four-year period in Eustache Creek. A univariate ANOVA model was created to detect significant relationships between individual habitat quality variables and fish populations. Overall, statistical analysis does not necessarily point to a significant increase in habitat quality for Eustache Creek, and the restored stream condition is still far from its reference condition. However, a non-statistical assessment of trends in individual habitat metrics shows an improvement in trout habitat quality. There was a significant increase in total fish densities in Eustache Creek over the study period. Additionally, there was a significant increase in total WCT, Adult WCT, and Adult Eastern Brook trout (EBT) densities over time. However, there was no statistically significant difference in total fish density, total WCT density, adult WCT density, total EBT density and adult EBT density between reference and treatment reaches, indicating that the increased fish populations may reflect the influence of external factors such as climatic variability rather than the improvement in habitat quality. No habitat variables are significantly correlated to total fish density. There was a statistically weak positive correlation between percent pool habitat and total fish density. While Eustache Creek appears to be trending toward improved fish habitat, the high variability of the habitat and fish data within certain reaches, including the reference reach, from year to year suggest that the stream is a seasonally and environmentally dynamic system to which fish populations are quite sensitive, and that recovery will be a long term process. Fish density in this watershed could be influenced by other factors of habitat quality such as food, stream temperature and seasonal and environmental variation. Best measures of habitat quality in this study were percent pool habitat, LWD frequency and LWD median diameter. Recommendations for future monitoring include: 1) continue monitoring for the next 15-20 years, 2) collect more pre-project data, 3) increase the number of sampling sites, 4) maintain consistency in sampling dates, number of netters and number of elec

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© Copyright 2010 Emily K. Thompson