Mitigation for the Construction and Operation of Libby Dam

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the stilling basin, we are not able to determine if burbot abundance in the reservoir has declined in recent years. We found no evidence of a significant trend of burbot abundance in Libby Reservoir from our spring gill netting data since 1990. However, gillnets might not provide an accurate indication of burbot population trends due to seasonal differences in movement and activity, and variable catch rates. Some investigators suggest that baited hoopnets are a more efficient capture method (Jensen 1986; Bernard et al. 1991). Paragamian and Hoyle (2003) found that burbot abundance in the lower Kootenai River in Idaho and British Columbia has also declined since 1995. However, by 1995, the abundance of burbot in the lower Kootenai River was substantially reduced from historic levels (Paragamian and Hoyle 2003). Paragamian and Hoyle (2003) reported burbot catch rates using baited hoop traps in the lower Kootenai River ranging from 0.055 burbot per trap day in 1995/1996 to a low of 0.006 burbot per trap day in 2002/2003. The decline of burbot abundance in the stilling basin below Libby Dam correlates to burbot catch rates that Paragamian and Hoyle (2003) reported in the lower Kootenai during the same time period (Figure 45; r 2 = 0.615; p < 0.05). Paragamian et al. (1999) concluded that two genetically dissimilar burbot populations existed in the Montana and Idaho/British Columbia portions of the Kootenai Basin, which suggests that the correlation we observed between our catch rates in the stilling basin and Paragamian and Hoyle’s catch rates in the lower Kootenai was not likely due to fish migration, but rather possible similar environmental conditions that may influence population dynamics of both stocks. Lower Kootenai Burbot CPUE 0.06 0.05 0.04 0.03 0.02 0.01 0 Y = 0.0068Ln(X) + 0.035 R 2 = 0.6152; P < 0.05 0 0.5 1 1.5 2 2.5 Stilling Basin Burobt CPUE 3 Figure 45. A regression analysis of mean burbot catch rates (burbot per trap day) for baited hoop traps in the stilling basin in the Kootenai River below Libby Dam and the lower Kootenai River (Paragamian and Hoyle 2003) between 1995/1996 and 2003/2003. 111
We believe that Libby Reservoir during the previous 12-15 years has stabilized in terms of biological production. Total fish abundance, as indexed by trends in gill net catch rates have stabilized since 1988. Fish and zooplankton species composition and abundance have also experienced similar trends. Mountain whitefish, rainbow trout and westslope cutthroat trout abundance all exhibited dramatic decreases in abundance (Figure 28) following the first ten years after reservoir filling, but have stabilized at much lower abundances than the pre-dam period. Fish species composition also shifted during the first 10 years after reservoir construction, but has also stabilized. Zooplankton abundance, species composition, and size distribution have also all been similar during the second half of the reservoir’s history. We attribute these trends toward trophic equilibrium to the aging process of the reservoir (Kimmel and Groeger 1986) and the operational history of Libby Dam during the past 15 years. Although all of the statistically significant trends observed for our macroinvertebrate monitoring on the Libby Creek Upper Cleveland Project are consistent with declining ecological integrity, the declines were relatively minor. The direction of change and taxa involved were consistent with changes caused by mild sedimentation, but were probably due to adjustments from an exceptional year at the beginning of the study and a return to more natural conditions. That is, the exceptionally low abundance of collectors in 2000, may have be responsible for some of the observed changes. The site will be monitored to ensure that sedimentation is not an issue. However, before we disregard the potential impairments, we should note that the restoration was relatively recent and there may be some associated ecosystem disturbance. Nonetheless, the evidence in this study suggests that these effects, if present are relatively minor. Two of the most tangible macroinvertebrate metrics that can be used to assess ecological integrity are Taxa Richness and EPT Richness because they summarize how many taxa (species, genera, families) inhabit the site. Both of these measures showed subtle improvements that were not statistically significant. We ran a post hoc power analysis and found that we had 81.2% power to detect a difference between the taxa richness of the 2 years at the Libby Creek site. Similarly, we found that the study had 27% Power to detect differences in EPT Richness. For future reference, we ran an analysis to show how replication could have improved the ability to detect differences in these two metrics (Figures 46 through 48). Based on these results, we will further evaluate the utility of modifying future sampling to improve our ability to detect differences between years. The rapid bioassessment classification we used for the Libby and Grave Creek classified both sites as moderately deviant from mountain reference conditions. It is important that these results are interpreted conservatively because they were not collected using the same procedures used to calibrate Marshall and Kerans (2003) biocriteria. In particular, the method used by FWP may increase the collection of midges (Diptera, Collector-gatherers), and be partially responsible for moderately deviant classification rating. However, it is also likely that the results could be indicative of sediment problems upstream in the watershed. 112
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Mitigation for the Construction and
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MITIGATION FOR THE CONSTRUCTION AND
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depth of burbot that were relocated
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ACKNOWLEDGEMENTS We are thankful to
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Juvenile Salmonid Population Estima
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deviation from reference conditions
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Figure 46. Minimal detectible diffe
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Chapter 2 Tables Table 1. Design sp
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INTRODUCTION Libby Reservoir was cr
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PROJECT HISTORY Montana Fish, Wildl
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2002 - Montana FWP collaborated wit
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DESCRIPTION OF STUDY AREA Subbasin
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Table 1. Current relative abundance
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Similar impacts have been observed
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2460 2440 2420 2400 2380 2360 2340
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construction and operation of Libby
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Chapter 1 Physical and Biological M
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Biological monitoring data was prov
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Figure 1. An aerial photograph of L
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antenna located approximately 5 cm
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We compared samples collected in Se
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extends downstream 131 m. This sect
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and reduced again to 28 ganged floa
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Results Bull Trout Redd Counts Grav
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Table 1. Bull trout redd survey sum
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Quartz Creek Bull trout redd counts
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Bull Trout Redds 40 35 30 25 20 15
Page 55 and 56: Keeler Creek Bull trout that spawn
Page 57 and 58: Burbot Monitoring Below Libby Dam T
Page 59 and 60: Table 2. Summary information for th
Page 61 and 62: 7000 6000 5000 Y = 45.246e 0.0055x
Page 63 and 64: The Libby FWP Mitigation Staff surg
Page 65 and 66: Table 2. (Continued) Capture locati
Page 67 and 68: Figure 18. Capture locations for a
Page 69 and 70: Table 4. T-test results. This table
Page 71 and 72: Figure 19. Montana Mountain Metrics
Page 73 and 74: Table 5. T-test results. This table
Page 75 and 76: Juvenile Salmonid Population Estima
Page 77 and 78: Grave Creek Juvenile salmonid monit
Page 79 and 80: Number Fish per 1000 Feet 100 80 60
Page 81 and 82: Libby Creek Section 1 of Libby Cree
Page 83 and 84: Figure 28. Rainbow trout, brook tro
Page 85 and 86: Pipe Creek Juvenile rainbow trout w
Page 87 and 88: Table 6. Average length and weight
Page 89 and 90: Catch per Net A. Mountain Whitefish
Page 91 and 92: Table 8. Kamloops rainbow trout cap
Page 93 and 94: 25000.0 20000.0 15000.0 10000.0 500
Page 95 and 96: Burbot per Trap Day 3 2.5 2 1.5 1 0
Page 97 and 98: Table 9. Average catch per net for
Page 99 and 100: Table 11. Percent composition of ma
Page 101 and 102: deviation = 0.052; Figure 43), with
Page 103 and 104: Table 12. Individual probability va
Page 105: Discussion Long-term monitoring of
Page 109 and 110: Figure 47. Minimal detectible diffe
Page 111 and 112: References Bahls, L., R. Bukantis,
Page 113 and 114: trout status report (below Kootenai
Page 115 and 116: Chapter 2 Stream Restoration and Mi
Page 117 and 118: food sources, as evidenced by the l
Page 119 and 120: Methods and Results Eureka Pond The
Page 121 and 122: spacing was 172.8 feet, which repre
Page 123 and 124: Figure 2. Vicinity Map for Upper Li
Page 125 and 126: Table 1. Design specifications for
Page 127 and 128: 70 60 50 40 30 20 10 0 500 1000 150
Page 129 and 130: Grave Creek Phase I Restoration Pro
Page 131 and 132: Table 4. Design specifications for
Page 133 and 134: 190.0 185.0 180.0 175.0 170.0 165.0
Page 135 and 136: educed the mean width and width to
Page 137 and 138: Table 7. Mean cross sectional area,
Page 139 and 140: Discussion The Grave Creek Phase I
Page 141 and 142: References Chisholm, I.M., M.E. Hen
Page 143 and 144: Appendix 148
Page 145 and 146: Table A2. Lower Grave Creek Demonst
Page 147 and 148: Table A4. Libby Creek depletion pop
Page 149 and 150: Table A7. Mean zooplankton densitie
Page 151 and 152: Table A9. Mean zooplankton densitie
Page 153: Table A13. Yearly mean total zoopla
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Mitigation for the Construction and Operation of Libby Dam

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