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Lake & Reservoir Habitat Management (>4 ha) Chapter 11

Lake & Reservoir Habitat Management (>4 ha) Chapter 11. Watershed Concerns. Sediment. Reduction in depth Loss of fish spawning sites Increased turbidity. Organic Matter Inputs. Detritus supports food web in turbid reservoirs BOD problems. Nutrients.

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Lake & Reservoir Habitat Management (>4 ha) Chapter 11

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  1. Lake & Reservoir Habitat Management (>4 ha)Chapter 11

  2. Watershed Concerns

  3. 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

  9. Lake Management

  10. Shoreline Erosion Problems • Wave action from wind, boats • Problems similar to watershed erosion

  11. Shoreline Erosion Controls • Naturally vegetated shoreline and littoral zone • Spawning habitat + cover • Problem in reservoirs with fluctuating water levels

  12. Shoreline Erosion Controls • Riprap • Spawning habitat

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

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

  15. Vegetation Control • Extensive growth of macrophtyes after “restoration” in 1970s • Refuge for prey fishes • Overabundance - stunting

  16. Vegetation Control • Mechanical controls • Weed harvesters • Chemical controls • Sonar, Aquashade • Biological controls • Grass carp

  17. 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

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

  19. Dewatering & Water Level Fluctuations • Dewatering to kill off eggs/nests of undesirable species, drive fish out of cover, consolidate/remove organic and inorganic sediments

  20. 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

  21. Habitat Diversity • Lake/reservoir shape - irregular shape produces protected habitats

  22. Habitat Diversity • Underwater structure - natural or artificial

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