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John D. Walrath

Seasonal Food Habits of Northern Pike and Smallmouth Bass in Coeur d’Alene Lake, Idaho. John D. Walrath Idaho Cooperative Fish and Wildlife Research Unit, Department of Fish and Wildlife Sciences, University of Idaho. Michael C. Quist

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John D. Walrath

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  1. Seasonal Food Habits of Northern Pike and Smallmouth Bass in Coeur d’Alene Lake, Idaho John D. Walrath Idaho Cooperative Fish and Wildlife Research Unit, Department of Fish and Wildlife Sciences, University of Idaho Michael C. Quist U.S. Geological Survey – Idaho Cooperative Fish and Wildlife Research Unit, University of Idaho Jon A. Firehammer Coeur d’Alene Tribe

  2. Westslope Cutthroat Trout Distribution Montana Washington Oregon Wyoming Idaho

  3. Coeur d’Alene Lake • Lake morphology • 12,742 ha • Maximum depth of 61 m • Mean depth of 24 m • Fish assemblage • 3 native sport fish species • 5 native nongame species • 16 introduced sport fish species • 1 introduced nongame species Spokane River Coeur d’Alene River Lake Creek St. Joe River Benewah Creek

  4. Restoration Activities

  5. Monitoring • Lake Creek • 1.7% juvenile-adult PIT tag returns • Benewah Creek • 2.3% juvenile-adult PIT tag returns

  6. Stratified random sampling 300 m sections Randomly assign a section per gear (18 total) Sampling Design • Sampled monthly • May – November (2012) • April – May (2013) • Sampled biweekly • March – June (2012) • March – May (2013) • Sampled monthly • July – November (2012) Cougar Bay Wolf Lodge Bay Windy Bay Benewah Lake

  7. Sampling Gears • Experimental gill nets • 1.5 – 2.0 h • 638 sets • Electrofishing • Pulsed DC – 3,000 W • 62.4 h

  8. Fish Processing • Length and weight • Aging structures • Spines, otoliths, fin rays, and cleithra • 10 fish per centimeter length group

  9. Northern Pike Catch Rates Electrofishing Gill netting

  10. Smallmouth Bass Catch Rates Electrofishing Gill netting

  11. Relative Weight Northern Pike Smallmouth Bass

  12. Size Structure

  13. Northern Pike Growth n = 735

  14. Northern Pike Growth n = 735

  15. Smallmouth Bass Growth n = 1,087

  16. Smallmouth Bass Growth n = 1,087

  17. Smallmouth Bass Growth n = 1,087

  18. Food Habits • Pulsed gastric lavage • High efficiency • 5 fish per centimeter length group • Preserved diet in 10% formalin • Laboratory processing • Prey identification • Invertebrates • Fishes • Back-calculated length and weight of prey items using diagnostic bones

  19. Food Habits • Frequency of occurrence • Prey-specific energy contribution

  20. Food Habits Specialization High BPC Dominant High WPC Rare Generalization

  21. Northern Pike

  22. Northern Pike

  23. Northern Pike

  24. Northern Pike

  25. Smallmouth Bass ≥150mm

  26. Smallmouth Bass ≥150mm

  27. Smallmouth Bass ≥150mm

  28. Smallmouth Bass ≥150mm

  29. What goes in = What comes out Bioenergetics Modeling Consumption = Metabolism + Waste + Growth Gonads Reproduction Consumption ∆Biomass Growth Respiration Basal metabolism Egestion - F Excretion - U Specific dynamic action Active metabolism Costs from digestion Costs from activity C = (R + S + A) + (F + U) + (ΔB + G)

  30. Bioenergetics Modeling • Wisconsin Model • Physiological parameters • Year class 2011 • Bevelheimer et al. (1985) • Year class 2008-2010 • Bean et al. (2010) • Water temperature • Food habits • Prey energy densities • Growth

  31. Bioenergetics Modeling

  32. Bioenergetics Modeling

  33. Westslope Cutthroat Trout

  34. Bioenergetics Modeling

  35. Westslope Cutthroat Trout

  36. Westslope Cutthroat Trout

  37. Conclusions Northern Pike Highest catch rates Spring gill nets Fast growth Smallmouth Bass Highest catch rates Fall electrofishing Slow growth

  38. Conclusions • Northern Pike • Dominant prey items • Kokanee and Yellow Perch • Highest occurrence of Cutthroat Trout predation in spring • Smallmouth Bass • Dominant prey items • Brown Bullhead, Yellow Perch, Kokanee, and Sculpin • Cutthroat Trout rarely consumed

  39. Conclusions • Bioenergetics • Seasonal growth • Greatest between fall and spring • Low Pc values • Prey availability • Low metabolic rates • Westslope Cutthroat Trout consumption • Highest for Northern Pike ages 2-4 • 2010 year class consumed ~50% of WCT biomass

  40. Next Steps Yield modeling Beverton-Holt Reduced predation on Westslope Cutthroat Trout

  41. Acknowledgments • Coeur d’Alene Tribe • Angelo Vitale • Dan Jolibois • Eric Hendricksen • Jason Smith • Idaho Department of Fish and Game • Jim Fredericks • Mark Liter • Steve Elle • University of Idaho • Carson Watkins • Chris Smith • Steve Whitlock • Travis Schill • Tiffani Wilson • Volunteers • Martha Castaneda • Isaiah Lee • Bryan Harper • Josh Sanchez • Mark Stanger • Liz Mamer • Debi Jensen • Kristi Stevenson • Wesley Field • Nick Porter • Christian Brown • Kayla Griffin • Erin Landers

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