Spada Lake Biological Assessment and Sport Fishery Evaluation
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Spada Lake Biological Assessment and Sport Fishery Evaluation Bob Pfeifer Washington Department of Fish and Wildlife Paul Tappel Fisheries Consultants Allan Vogel ZP's Taxonomic Services Murray Schuh Snohomish County PUD No. 1 Wayne Brunson Washington Department of Fish and Wildlife December 1998 Table of Contents Acknowledgments ........................................................... xix Executive Summary ......................................................... xxi Background .................................................................. 1 Project History and Mitigation Terms ("Stage 11") .............................. 1 Creel Sweys and Fishery Performance ...................................... 3 Relationships to Current Fishery Management Goals and Objectives ............... 6 1995-97 Study Objectives ................................................. 8 DescriptionoftheStudyArea .................................................... 9 Basin Geologic. Vegetative. and Development History .......................... 9 BasinClimateData ..................................................... 11 Reservoir Morphology and Operation ....................................... 12 Morphometry .................................................... 12 Inflow/Outflow Relationships ....................................... 14 Annual Drawdown and Summer Rearing Area .......................... 17 Fish Species and Brief Life History ......................................... 18 Rainbowandcutthroat ............................................ 18 Brown Bullhead (Literature Review) .................................. 21 EastemBrookChar ............................................... 24 WaterQuality ................................................................ 27 Dissolved Oxygen. Temperature. Transparency. and the Euphotic Zone ............27 Methods ........................................................ 27 Results and Discussion ............................................ 31 Conductivity. pH. and Other Miscellaneous Water Quality Data ..................41 Methods. Results and Discussion .................................... 41 Conclusions ........................................................... 43 SecondaryProduction ......................................................... 45 Zooplankton ........................................................... 45 Methods ........................................................ 45 Spada Lake Fishery Study: 1995-97 I Table of Contents ............................................ Results and Discussion . 48 Species Composlt~on........................................ 48 Density and Standing Crop .................................. -52 Descriptive Population Dynamics .............................. 58 Indicators of Trophic Status ................................... 58 Vertical Distribution ........................................ 59 Abundance, Size, and Value as Fish Food ........................ 61 Conclusions ..................................................... 71 Benthos .............................................................. 72 Methods ........................................................ 72 Results and Discussion ........................................... -73 Conclusions ..................................................... 84 TertiaryProduction ........................................................... 85 Fish Relative Abundance, Length Frequency, and Sex Ratio ..................... 85 Methods ........................................................ 85 Results and Discussion ............................................ 89 Conclusions .................................................... 101 Estimates of Trout Immigration, Mortality, Population Size, and Standing Stock .... 102 Methods ....................................................... 102 Results and Discussion ........................................... 105 Conclusions .................................................... 110 Trout Age, Growth, and Condition ........................................ 110 Methods ........................................................ 111 AgeandGrowth ........................................... 111 ......................................... LengthatMaturity. 116 Condlt~on................................................ 117 Results and Discussion ........................................... 119 AgeandGrowth. ........................................... 119 Cond~hon................................................ 133 Concli~sions.................................................... 139 TroutFoodHabits ..................................................... 140 Methods ....................................................... 140 Results and Discussion ........................................... 141 Conclusions .................................................... 154 Trout Spawning Period and Age at Maturity ................................. 157 Methods ....................................................... 157 Results and Discussion ........................................... 159 Conclusions .................................................... 161 Trout Parasitism and Mortality ........................................... 162 Methods ....................................................... 162 Results and Discussion ........................................... 164 Spa& Lake Fishery Study: 1995-97 ii Table of Contents Conclusions .................................................... 181 Fish Harvest (Yield) and Recreational Use Levels ............................ 182 Methods ....................................................... 182 Results and Discussion ........................................... 183 Conclusions .................................................... 186 Fishery Management Recommendations and Attainment of Management Objectives ....... 195 Attainment of Management Objectives ..................................... 195 Mitigation of Stage I1 Impacts ...................................... 204 Summary of Management Recommendations ................................ 206 Summary of Additional Research Needs .................................... 206 References and Personal Communications ........................................ 209 Appendices ................................................................. 229 Spada Lake Fishery Study: 1995-97 iii Table of Contents This page intentionally left blank Spada Lake Fkhery Siudy: 1995-97 iv Table of Contents List of Tables Table 1. Estimated total fish harvest from Spada Lake. 1979 through 1995 ............... 4 Table 2 . Trout catch and harvest rates from Spada Lake. 1979 through 1995 .............. 4 Table 3 . Angler trips and effort levels on Spada Lake. 1979 through 1995 ................ 5 Table 4 . Estimated annual yield of the Spada Lake sport fishery. 1979 through 1995 ........ 6 Table 5 . Morphometric and operational data for Spada Lake .......................... 12 Table 6 . Monthly retention and flushing times for low (1992). mean (1989). and high (1997) water years in Spada Lake. and for selected other years. 1987 through 1997 . 16 Table 7 . Number of days per month of reservoir spill. and at or above elevation 1445.0 A (msl). 1987through1997 .............................................. 17 Table 8 . Heat budgets for Spada Lake. Snohomish County. Washington. 1989 through 1997 ............................................................... 36 Table 9 . Heat budgets of Spada Lake. Snohomish County. Washington. and other lakes aroundtheworld ..................................................... 37 Table 10. Paired Secchi transparency readings. Spada Lake. 1995-96 .................... 39 Table 11. The occurrence of zooplankton species in Spada Lake. Washington. 1979 through 1997............................................................... 50 Table 12. Historic zooplankton peak densities in Spada Lake. Washington ................ 52 Table 13. Weighted mean zooplankton densities (TJo.fm3) calculated from Clarke-Bumpus tows in Spada Lake. Washington. 1997 ................................... 53 Table 14. Zooplankton densities in Spada Lake in comparison to other lakes and reservoirs ofthePacificNorthwest ............................................... 57 Table 15. Seasonal mean or annual range in total lengths (mrn) of Spada Lake zooplankton. with similar data from other lakes or reservoirs ............................. 64 Table 16. The relationship between Spada Lake benthic samples in 1997 and frequency of exposureduetodrawdown ............................................. 74 Table 17. Dates. Spada Lake elevations. depths sampled. bottom elevations sampled. and sample codes for benthic invertebrate samples. 1997 ......................... 75 Table 18. Benthic invertebrate densities (no.im2) near Site 2 (WDG 1982) or inN Bay 2 ofSpadaLake,197 9.80and1997 ........................................ 76 Spada Lake Fishery Study: 1995-97 v List of Tables Table 19. Comparisons of chironomid and oligochaete densities (noIm2) in Spada Lake, 1979-8Oand1997 .................................................... 77 Table 20. Occurrence of benthic invertebrates in benthic samples and trout diets from Spada Lake,1979-80,1986,and1997 .......................................... 78 Table 21. Latesummer mean densities (no.lm2) of benthic invertebrates from Spada Lake, Washington, and other waters of similar latitude . .79 Table 22. Mean numbers of benthic invertebrates (Im2) from the N Bay 2 transect of Spada Lake, August 5, 1997 (pool elevation 1438' msl) . .80 Table 23. A comparison