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

Chapter 11Chapter 11

Watershed ConcernsWatershed Concerns

SedimentSediment

Reduction in depthReduction in depth

Loss of fish Loss of fish spawning sitesspawning sites

Increased turbidityIncreased turbidity

Organic Matter InputsOrganic Matter Inputs

DetritusDetritus supports supports food web in turbid food web in turbid reservoirsreservoirs

BOD problemsBOD problems

NutrientsNutrients EutrophicationEutrophication - -

natural aging of natural aging of lake brought on by lake brought on by increasing increasing productivityproductivity

Cultural Cultural eutrophicationeutrophication - - excessive delivery, excessive delivery, build-up of build-up of nutrients leading to nutrients leading to excessive plant excessive plant growthgrowth

AcidificationAcidification

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

ContaminantsContaminants

Point-source + Point-source + nonpoint-source nonpoint-source pollutants + pollutants + bioaccumulationbioaccumulation = = consumption consumption advisoriesadvisories

Thermal PollutionThermal Pollution

Temperature shockTemperature shock Growth, spawning Growth, spawning

problemsproblems Gas bubble disease Gas bubble disease

(nitrogen narcosis)(nitrogen narcosis) EntrainmentEntrainment - -

smaller, pass throughsmaller, pass through ImpingementImpingement - -

larger, trapped on larger, trapped on screensscreens

Lake ManagementLake Management

Shoreline Erosion Shoreline Erosion ProblemsProblems

Wave action from Wave action from wind, boatswind, boats

Problems similar Problems similar to watershed to watershed erosionerosion

Shoreline Erosion Shoreline Erosion ControlsControls

Naturally vegetated Naturally vegetated shoreline and shoreline and littoral zonelittoral zone

Spawning habitat + Spawning habitat + covercover

Problem in Problem in reservoirs with reservoirs with fluctuating water fluctuating water levelslevels

Shoreline Erosion Shoreline Erosion ControlsControls

RiprapRiprap

Spawning habitatSpawning habitat

FertilizationFertilization To increase fish To increase fish

productionproduction Success limited to:Success limited to:

Oligotrophic lakesOligotrophic lakes Ponds (great care)Ponds (great care)

Generally causes Generally causes problems in problems in natural lakes and natural lakes and reservoirs (size, reservoirs (size, existing existing productivity)productivity)

Vegetation ControlVegetation Control Enhanced fishery Enhanced fishery

up to ~20% up to ~20% coverage by coverage by macrophytesmacrophytes

Problems at higher Problems at higher levels (e.g., Lake levels (e.g., Lake Winona)Winona)

Vegetation ControlVegetation Control Extensive growth Extensive growth

of macrophtyes of macrophtyes after “restoration” after “restoration” in 1970sin 1970s

Refuge for prey Refuge for prey fishesfishes

Overabundance - Overabundance - stuntingstunting

Vegetation ControlVegetation Control Mechanical Mechanical

controlscontrols Weed harvestersWeed harvesters

Chemical controlsChemical controls Sonar, AquashadeSonar, Aquashade

Biological controlsBiological controls Grass carpGrass carp

Stratification & AerationStratification & Aeration

Dissolved ODissolved O22 limits habitat during summer limits habitat during summer Destratification via aeration expands habitat for Destratification via aeration expands habitat for

warmwater fishwarmwater fish Can be modified to provide tiered habitat for Can be modified to provide tiered habitat for

warm- & coldwater fishwarm- & coldwater fish

Stratification & AerationStratification & Aeration

Aeration can also be used in winter to Aeration can also be used in winter to prevent Oprevent O22 depression below ice, reduce depression below ice, reduce or eliminate winterkillor eliminate winterkill

Dewatering & Water Dewatering & Water Level FluctuationsLevel Fluctuations

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

Dewatering & Water Dewatering & Water Level FluctuationsLevel Fluctuations

Flooding terrestrial vegetation every few Flooding terrestrial vegetation every few years to produce years to produce trophic upsurgetrophic upsurge

Increase overall lake productivity, Increase overall lake productivity, produce strong year-classes of walleye, produce strong year-classes of walleye, white bass, white crappiewhite bass, white crappie

Habitat DiversityHabitat Diversity Lake/reservoir Lake/reservoir

shape - irregular shape - irregular shape produces shape produces protected habitatsprotected habitats

Habitat DiversityHabitat Diversity Underwater Underwater

structure - natural structure - natural or artificialor artificial