Lakes & Large Impoundments Chapter 22

Lakes & Large Impoundments Larger size means greater complexity

Differences between Lakes and Reservoirs Impoundments have greater shoreline development

Differences between Lakes and Reservoirs Impoundments have limited littoral zones Steeper sloping basins

Differences between Lakes and Reservoirs Impoundments have higher water flow-through Turbidity and sediment input affects invertebrate production, fish spawning areas

Differences between Lakes and Reservoirs Impoundments have wide internal variation in physicochemical factors

Differences between Lakes and Reservoirs Impoundments have young age Limited fish assemblage (stocking?)

Controls of Fish Production Trophic state model - “from the bottom up” Production, biomass of higher trophic levels controlled by nutrients, primary production

Controls of Fish Production Food web models - “from the top down” Consumer controlled - fish predation determines structure, abundance of prey Both likely operate simultaneously

Increase Fish Yield By: Increasing food resource base (fertility) Increasing transfer efficiency between trophic levels

Problem of Variable Recruitment Biological variation Climatic variation Water level fluctuations Impoundment age

Reservoir Age

Assessing Fish Populations Direct approach - growth rate, recruitment, size structure Relative weight, proportional stock density

Assessing Fish Populations Indirect approach - examination of fishery-impacted components Primary, secondary productivity, zooplankton size structure

Management Problems