Lecture 2.7 Restoration of Lake Superior Lake Trout: Stocking

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Lecture 2.7 Restoration of Lake SuperiorLake
Trout Stocking Removals

• Natural Resources 250
• Michael J. Hansen
• Professor of Fisheries

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Historical Perspective
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Lake Trout Restoration

• Great Lakes facts.
• Lake trout population dynamics.
• Causes of stock collapse.
• Restoration strategies.
• Stock restoration progress.

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Lake Trout RestorationGreat Lakes Facts

• Great Lakes contain 20 of earths freshwater.
• Lake Superior contains 10 of earths freshwater.
• Lake Superior 31,700 mi2.
• Lake Huron 23,000 mi2.
• Lake Michigan 22,300 mi2.
• Lake Erie 9,910 mi2.
• Lake Ontario 7,340 mi2.

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Lake Trout RestorationGreat Lakes Facts

• Great Lakes drain nearly 200,000 mi2 of U.S.
  (eight states) and Ontario landscape.
• Great Lakes shoreline is more than 10,000 miles
  long.

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Lake Trout RestorationLake Trout Population
Dynamics
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Lake Trout Restoration
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Lake Trout RestorationCauses of Stock Collapse

• Fishery exploitation.
• Fisheries sequentially exploited stocks within
  each Great Lake.
• Fisheries collapsed sequentially in Lake Huron,
  Lake Michigan, and Lake Superior.

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Lake Trout YieldLake Huron
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Lake Trout YieldLake Michigan
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Lake Trout YieldLake Superior
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Lake Trout RestorationCauses of Stock Collapse

• Sea lamprey predation.
• Welland Canal opened in 1829 (overhead).
• Sea lampreys invaded upper Great Lakes
• Lake Erie in 1921
• Lake Huron in 1932
• Lake Michigan in 1936 and
• Lake Superior in 1946.

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Sea Lamprey AbundanceLake Huron
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Sea Lamprey AbundanceLake Michigan
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Sea Lamprey AbundanceLake Superior
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Lake Trout RestorationRestoration Strategies

• Lake trout stocking.

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Lake Trout RestorationRestoration Strategies

• Sea lamprey control.

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Lake Trout RestorationRestoration Strategies

• Fishery closures.
• Prior to 1962, commercial fisheries were
  encouraged to harvest lake trout before sea
  lampreys killed the remaining fish.
• After 1962, when sea lamprey control was known to
  be effective, recreational and commercial fishing
  were closed.

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Lake Trout RestorationStock Restoration Progress

• Offshore stocks exhibited characteristic pattern
  of recovery from few surviving fish at remote
  locations.

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Lake Trout AbundanceLake Superior - Stannard Rock
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Lake Trout AbundanceLake Superior - Isle Royale
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Lake Trout AbundanceLake Superior - Gull Island
Shoal
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Lake Trout RestorationStock Restoration Progress

• Inshore stocks exhibited different pattern of
  recovery that was related to reproduction of
  hatchery-reared fish.

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Lake Trout AbundanceLake Superior - Michigan
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Lake Trout AbundanceLake Superior - Wisconsin
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Lake Trout AbundanceLake Superior - Minnesota
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Lake Trout RestorationStock Restoration Progress

• Stock status at present suggests that stocks have
  recovered throughout much of the lake, so
  stocking can be ceased!

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Lake Trout AbundanceLake Superior - Michigan
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Lake Trout AbundanceLake Superior - Michigan
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Lake Trout AbundanceLake Superior - Michigan
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Questions?