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Importance of Protecting Lake Trout

Importance of Protecting Lake Trout. 250,000 lakes in Ontario 1% of these contain lake trout Central/eastern Ontario has >1/3 of lakes Provincial responsibility to preserve. Why Protect Lake Trout Waters?. Why Protect Lake Trout Waters?. Represents 20-25% of world ’s supply

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Importance of Protecting Lake Trout

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  1. Importance of Protecting Lake Trout

  2. 250,000 lakes in Ontario • 1% of these contain lake trout • Central/eastern Ontario has >1/3 of lakes • Provincial responsibility to preserve Why Protect Lake Trout Waters?

  3. Why Protect Lake Trout Waters? • Represents 20-25% of world’s supply • Largest area of lake trout waters • Ontario has greatest responsibility in world

  4. Lake Trout requirements =

  5. Phosphorous Affects Oxygen =

  6. Lake Trout Lake Protection • Province is committed to protecting fish habitat • Cooperative effort with municipalities • Provincial Policy Statement • Official Plan is the planning tool

  7. Why Protect Lake Trout? • Native only to North America • Native stocks found on Canadian Shield • Isolated 10,000 years ago • Lake trout stocks genetically dissimilar • Once lost, no way to replace it • Keystone species, indicator of ecosystem health

  8. Lake Trout Life History • Need deep, well oxygenated, cold water lake environments to thrive • Late summer critical • Slow growing, late maturing, low productive potential

  9. Lake Trout vs Walleye

  10. Human Stressors

  11. Mean Volume Weighted Hypolimnetic Dissolved Oxygen (MVWHDO) • Criterion developed by Dr. David Evans in 1993 • Activity levels of lake trout limited by concentration of oxygen in water • Reduced oxygen affects swimming ability, feeding, avoidance of predators, growth and survival • Juveniles more sensitive • At temperatures of 4-14C, oxygen concentrations of 4.4, 5.8 and 7.1 mg/L limit activity to ¼, ½ and ¾, respectively • 7 mg/L provide for most daily life support activities

  12. Additional Supportive Data • Independent surveys of lake trout populations in southern Ontario: • Lake trout populations good to excellent when MVWHDO 7-8 mg/L • Recruitment average to poor when MVWHDO < 6 mg/L

  13. The Lake Trout Policy • Policy proposal using MVWHDO (7.0 mg/L) posted on Environmental Bill of Rights Registry (EBR) for public comment in early 2006 • EBR decision notice posted May 29, 2006 • Lake trout lakes listed in ‘Inland Ontario Lakes Designated for Lake Trout Management’ available at: www.mnr.gov.on.ca/mnr/ebr/lake_trout/index.html • Revisions will require posting on EBR Registry for public comment • Policy implemented Province-wide

  14. Historical MVWHDO For Buck Lake Recommended concentration of 7 mg/L South Basin • Sept. 19, 1978 – 7.87 mg/L • Sept. 01, 1987 – 5.27 mg/L • Sept. 06, 2007 – 5.91 mg/L North Basin • Sept. 06, 2007 – 4.75 mg/L

  15. Buck Lake Stocking History • three walleye stocking episodes between 1935 & 1948 (100,000 to 250,000) • 11 smallmouth bass stocking episodes between 1935 & 1956 • 1st record of lake trout stocking in 1949 with stocking each year between 1959 & 1989, average 4,000 annually • 6,000 genetically marked lake trout stocked in 1991 & 1992

  16. Historical Fish Assessment

  17. 1992 Buck Lake SLIN Catch (total no. fish)

  18. 1992 Buck Lake SLIN • 0.6 lake trout per net • 32 clipped lake trout (70%) • Mean total length: 39.7 cm (15.6 in) • Mean fork length: 35.8 cm (14.1 in) • Mean weight: 553 gms (1.2 lbs)

  19. 1997 Buck Lake SLIN • 1997, Spring Littoral Index Netting (SLIN) • Short sets (30 minutes), small mesh (1.5”,2.0” and 2.5”) • Spring, ice out until surface temperature reaches 13C • May 6-23 • Set 59 nets at randomly selected sites

  20. 1997 Buck Lake SLIN • 0.44 lake trout per net • 17 clipped (65%) • Mean age: 6.6 yrs • Mean total length: 44.3cm (17.4 in) • Mean fork length : 40.9cm (16.1 in) • Mean weight: 875 gms (1.9 lbs)

  21. 1997 Buck Lake SLIN –lake trout age at size

  22. Summer Profundal Index Netting (SPIN) • Season: mid-July to mid-September • Before thermocline collapses • Set duration: 2 hours • Net length: 64 m (210 ft) with 8 mesh sizes • Depth ranges: 10-20 m; 20-30m; 30-40m • > 3 mg/L dissolved oxygen

  23. SPIN Objectives • Obtain point-in-time estimate of relative area weighted density of lake trout (>300mm) • Obtain representative sample of lake trout population for diagnostic assessment of biological integrity

  24. 2007 Buck Lake SPIN • 39 net sets, 365 ha sampled (682 ha total) • Total 41 lake trout caught >300 mm • Estimated density of 3.4 lake trout >300 mm per ha • Population estimate of 1,233 lake trout • Confidence limits: 465 to 2,021 lake trout (68% predicted level) • Mean length total catch: 35.4 cm (13.9 in)

  25. 2007 Buck Lake SPIN – Lake Trout Lengths

  26. Buck vs Loughborough Lake SPINS

  27. What can Buck Lake Landowners Do? • Work with municipality (Official Plan) & fellow land owners to support protection & enhancement of lake trout habitat • Work with fellow land owners to reduce nutrient inputs • Water level manipulation? • Creel survey – what’s coming out? • Assessment of other fish species?

  28. Perfect ending to a day on the lake

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