Lakes

1
Lakes Large ImpoundmentsChapter 22
2
Lakes Large Impoundments

• Larger size means greater complexity

3
Differences between Lakesand Reservoirs

• Impoundments have greater shoreline development

4
Differences between Lakesand Reservoirs

• Impoundments have limited littoral zones
• Steeper sloping basins

5
Differences between Lakesand Reservoirs

• Impoundments have higher water flow-through
• Turbidity and sediment input affects invertebrate
  production, fish spawning areas

6
Differences between Lakesand Reservoirs

• Impoundments have wide internal variation in
  physicochemical factors

7
Differences between Lakesand Reservoirs

• Impoundments have young age
• Limited fish assemblage (stocking?)

8
Controls of Fish Production

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

9
Controls of Fish Production

• Food web models - from the top down
• Consumer controlled - fish predation determines
  structure, abundance of prey
• Both likely operate simultaneously

10
Increase Fish Yield By

• Increasing food resource base (fertility)
• Increasing transfer efficiency between trophic
  levels

11
Problem of Variable Recruitment

• Biological variation
• Climatic variation
• Water level fluctuations
• Impoundment age

12
Reservoir Age
13
Assessing Fish Populations

• Direct approach - growth rate, recruitment, size
  structure
• Relative weight, proportional stock density

14
Assessing Fish Populations

• Indirect approach - examination of
  fishery-impacted components
• Primary, secondary productivity, zooplankton size
  structure

15
Management Problems