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Lakes & Large Impoundments Chapter 22
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Lakes & Large Impoundments
Larger size means greater complexity
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Differences between Lakes and Reservoirs
Impoundments have greater shoreline development
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Differences between Lakes and Reservoirs
Impoundments have limited littoral zones Steeper sloping basins
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Differences between Lakes and Reservoirs
Impoundments have higher water flow-through Turbidity and sediment input affects invertebrate production, fish spawning areas
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Differences between Lakes and Reservoirs
Impoundments have wide internal variation in physicochemical factors
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Differences between Lakes and Reservoirs
Impoundments have young age Limited fish assemblage (stocking?)
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Controls of Fish Production
Trophic state model - “from the bottom up” Production, biomass of higher trophic levels controlled by nutrients, primary production
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Controls of Fish Production
Food web models - “from the top down” Consumer controlled - fish predation determines structure, abundance of prey Both likely operate simultaneously
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Increase Fish Yield By:
Increasing food resource base (fertility) Increasing transfer efficiency between trophic levels
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Problem of Variable Recruitment
Biological variation Climatic variation Water level fluctuations Impoundment age
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Reservoir Age
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Assessing Fish Populations
Direct approach - growth rate, recruitment, size structure Relative weight, proportional stock density
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Assessing Fish Populations
Indirect approach - examination of fishery-impacted components Primary, secondary productivity, zooplankton size structure
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Management Problems
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