Lake

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Lake Reservoir Habitat Management (gt4
ha)Chapter 11
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Watershed Concerns
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Sediment

• Reduction in depth
• Loss of fish spawning sites
• Increased turbidity

4
Organic Matter Inputs

• Detritus supports food web in turbid reservoirs
• BOD problems

5
Nutrients

• Eutrophication - natural aging of lake brought on
  by increasing productivity
• Cultural eutrophication - excessive delivery,
  build-up of nutrients leading to excessive plant
  growth

6
Acidification

• Poor buffering capacity acid deposition
  reproductive failure, gill damage, ion imbalance
  (homeostasis)

7
Contaminants

• Point-source nonpoint-source pollutants
  bioaccumulation consumption advisories

8
Thermal Pollution

• Temperature shock
• Growth, spawning problems
• Gas bubble disease (nitrogen narcosis)
• Entrainment - smaller, pass through
• Impingement - larger, trapped on screens

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Lake Management
10
Shoreline Erosion Problems

• Wave action from wind, boats
• Problems similar to watershed erosion

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Shoreline Erosion Controls

• Naturally vegetated shoreline and littoral zone
• Spawning habitat cover
• Problem in reservoirs with fluctuating water
  levels

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Shoreline Erosion Controls

• Riprap
• Spawning habitat

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Fertilization

• To increase fish production
• Success limited to
• Oligotrophic lakes
• Ponds (great care)
• Generally causes problems in natural lakes and
  reservoirs (size, existing productivity)

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Vegetation Control

• Enhanced fishery up to 20 coverage by
  macrophytes
• Problems at higher levels (e.g., Lake Winona)

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Vegetation Control

• Extensive growth of macrophtyes after
  restoration in 1970s
• Refuge for prey fishes
• Overabundance - stunting

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Vegetation Control

• Mechanical controls
• Weed harvesters
• Chemical controls
• Sonar, Aquashade
• Biological controls
• Grass carp

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Stratification Aeration

• Dissolved O2 limits habitat during summer
• Destratification via aeration expands habitat for
  warmwater fish
• Can be modified to provide tiered habitat for
  warm- coldwater fish

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Stratification Aeration

• Aeration can also be used in winter to prevent O2
  depression below ice, reduce or eliminate
  winterkill

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Dewatering Water Level Fluctuations

• Dewatering to kill off eggs/nests of undesirable
  species, drive fish out of cover,
  consolidate/remove organic and inorganic sediments

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Dewatering Water Level Fluctuations

• Flooding terrestrial vegetation every few years
  to produce trophic upsurge
• Increase overall lake productivity, produce
  strong year-classes of walleye, white bass, white
  crappie

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Habitat Diversity

• Lake/reservoir shape - irregular shape produces
  protected habitats

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Habitat Diversity

• Underwater structure - natural or artificial