Mitigation for the Construction and Operation of Libby Dam

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Libby Reservoir Zooplankton Monitoring Zooplankton species composition and abundance within Libby Reservoir has remained relatively stable during the past several years (Appendix Tables A7-A13). Since 1997, Cyclops and Daphnia have been the first and second most abundant genera of zooplankton present in the reservoir (Figure 41). Other lesser abundant genera in decreasing order of abundance include Diaptomus, Bosmina, Diaphanosoma, Epichura and Leptodora (Figure 41). Zooplankton abundance within the reservoir varies by season (Table 12; Figure 42). The results from 7 analysis of variance procedures that tested for differences in monthly zooplankton abundance (by species) indicated that at least one month was significantly different from other months in 2003 for the most abundant 7 species of zooplankton (Table 12). We did not perform multiple comparisons required to determine pairwise comparisons. Although zooplankton abundance varies within a season, seasonal peaks in abundance over the past six years (Figure 42) have remained relatively consistent across years. For example, Daphnia abundance has peaked during July each year except 2003 (June peak) since 1997, Diaphanosoma abundance has peaked in September during 6 of the last 7 years, Diaptomus has peaked during October during 4 of the last 7 years, and Cyclops has peaked in June during 4 of the last 7 years. In most cases when the annual peak differed from the mean peak, the difference was not more than several weeks. Our sampling design stratified the reservoir into thirds, and although each stratum was long (> 58 km), we found only weak evidence that zooplankton abundance differed between the three sampling areas (Tenmile, Rexford, and Canada) in 2003 (Table 12). For the 7 most abundant species of zooplankton in the reservoir at the three sites, we only found significant differences (by species) for 8 out of the possible 21 comparisons. When significant differences did occur between sampling location, there was no clear trend in terms of whether zooplankton abundance was always highest for most downstream site. During 2003, abundance estimates of Daphnia, Diaptomas, Cyclops, Leptodora, and Epischura differed between at least one of possible three comparisons between sampling areas. Subsequent multiple comparisons indicated that Daphnia densities were significantly higher at the Rexford and Canada sites than the Tenmile site and Diaptomas densities were significantly higher at the Rexford site than the Tenmile site, Cyclops abundance at Rexford was significantly higher than the Canada and Tenmile sites, Leptodora abundance was significantly higher at the Canada site than Tenmile and Rexford sites, and Epischura densities were significantly higher at the Rexford site than the Canada site. The month and area interaction term was significant for Bosmina, Cyclops, and Leptodora in 2003 (Table 12). Although the abundance of zooplankton of the genus Daphnia in 2003 was the highest during the previous 8 years, the trend has remained particularly stable in terms of abundance (Figure 41) and size (Figures 43 and 44) during the past several years. Mean annual Daphnia densities in Libby Reservoir from 1997 through 2003 have averaged 1.94 Daphnia /liter (standard deviation = 0.59/liter; Figure 43). Mean Daphnia length has also varied relatively little since 1991, averaging 0.90 mm (standard deviation = 0.05; Figure 44). Most Daphnia since 1993 are between 0.5 – 1.5 mm, with majority of Daphnia being represented in the smaller size class 0.5 – 0.99 mm (mean annual proportion = 0.61, standard 105
deviation = 0.052; Figure 43), with the majority of the remainder in the size class 1.0 – 1.499 (mean annual proportion = 0.336, and standard deviation = 0.036). Daphnia larger than 1.5 mm have on average comprised less than 5% of the total since 1993 (Figure 43). Number per Liter 12 10 8 6 4 2 0 1997 1998 1999 2000 2001 2002 2003 140 120 100 80 60 40 20 0 Number per Cubic Meter Year Daphnia Bosmina Diaptomus Cyclops Diaphanosoma Leptodora Epischura Figure 41. Annual zooplankton abundance estimates for 7 genera observed in Libby Reservoir from 1997-2003. Abundance for Epischura and Leptodora are expressed in number per cubic meter. All other densities are expressed as number per liter. The data utilized for this figure are presented in Appendix Table A13. 106
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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
Page 49 and 50: Table 1. Bull trout redd survey sum
Page 51 and 52: Quartz Creek Bull trout redd counts
Page 53 and 54: 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: Table 11. Percent composition of ma
Page 103 and 104: Table 12. Individual probability va
Page 105 and 106: Discussion Long-term monitoring of
Page 107 and 108: We believe that Libby Reservoir dur
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
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Table A9. Mean zooplankton densitie
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Table A13. Yearly mean total zoopla
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Mitigation for the Construction and Operation of Libby Dam

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