Streams and Lakes

1
Streams and Lakes

• Environmental
• temperature
• water flow
• substrate
• light availability
• water level variation
• chemistry
• pH, dissolved O2, etc.

• Biological
• predator-prey
• resource partitioning
• symbiosis

2
Temperature and Streams

• Warm-water streams
• gt 24-26C for extended periods
• Cypriniformes
• Cyprinidae (minnows)
• Catostomidae (suckers)
• Perciformes
• Centrarchidae (bass, sunfishes)
• Percidae (darters)

• Cold-water streams
• lt 24-26 most often
• Salmoniformes
• Salmonidae (trout)
• Scorpaeniformes
• Cottidae (sculpins)

3
Temperature and Lakes

• Warm-water lakes
• Centrarchidae (bass, sunfishes)
• Percidae (walleye)
• Cold-water lakes
• Salmonidae (trout)
• Lakes stratification
• Epilimnion
• Hypolimnion
• Thermocline

4
Stream Gradient

• Amount of vertical drop over horizontal distance
• slope of the land
• How does stream gradient relate to water
  velocity?
• How does stream gradient relate to substrate?
• Fauna characteristic of stream gradient
• dace, sculpins in high gradient
• percids and centrarchids increase at lower
  gradients

5
Stream Order

• Merging streams increases size, increase stream
  order
• As stream order increases, water volume
  increases, stream gradient decreases
• How would the community change with increasing
  stream order?
• Fauna characteristic of stream order

6
Water Movement in Lakes

• Limited water movement
• Wind moves the water
• How would wind motion affect active fishes?

• How does stratification affect the distribution
  of oxygen and nutrients?

7
Predator-Prey Interactions

• Food chains
• trophic cascade
• Key predators influence size and abundance of
  other species
• Structure provides protection from predation
• Large predators protect larvae of their prey
• How?

8
Resource Partitioning

• Ecological segregation due to morphology
• Further partitioning due to behavioral
  differences
• Increases complexity of the community of fishes

Salmonidae (rover-predator)
Cyprinidae (benthic insectivore)
Catostomidae (benthic suction feeder)
Cottidae (noctural ambush feeder)