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Fish in Lakes

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					Fish in Lakes
          Lake Food Chain




 Generally represent the end of the food
  chain in most lakes
 Only a small fraction of the energy fixed in
  the system makes it to this level
         Lake Food Chain




          group because of effects they
 Important
 can have on all other levels of living things
 in lakes
Feeding Categories
          Piscivores   - feed
          on fish

          Basses,   pikes,
          walleye
Feeding Categories
          Planktivores  - feed
           on phytoplankton,
           zooplankton
          Visual particulate
           feeders or strainers
          Young of many
           species, clupeids
           like alewife
Feeding Categories
          Benthivores - pick
          materials off bottom

          Macroinvertebrates,
          algae, plants, detritus

          Suckers
Feeding Categories
          Omnivores - feed
          on everything

          Carp,gizzard shad
          (planktivore
          tendencies)
         Trophic Control
 Each trophic group
 is important, but
 piscivores &
 omnivores have
 more overall
 control on the
 entire system
           Trophic Control
 Strong populations
 of piscivores can
 keep other fish
 types in check and
 keep system
 “balanced”

 Top-down   control
           Out of Control!
 In absence of
  predators, other
  fish types can
  dominate, affect
  other lake
  components
 Planktivores - shad
 Benthivores -
  stunted bluegill
The Carp Cascade
         Feeding activities of
          carp can modify
          littoral substrate and
          muddy the water
         Macrophytes cannot
          grow
         Muddy water -
          reduced
          transparency,
          reduced
          phytoplankton,
          reduced zooplankton,
          etc.
         The Bottom Line




 Presence or absence of a single species
 may have significant impact on the
 functioning of the entire lake
Fish Productivity
            Varies greatly
             among different
             fishes

            Fishes feeding
             nearer the base of
             the food chain
             (herbivores) are
             more productive
             than predatory forms
Fish Productivity
          The younger the fish
           population (mean
           age), the more
           productive it is
          Young fish, greater
           % of food intake to
           growth
          Older fish, greater %
           of food intake to
           maintenance
Fish Productivity
            In temperate zone
             lakes, production of
             fish limited mostly to
             spring, summer,
             autumn

            Considerably lower
             than in tropical lakes
Fish Productivity
            Tropics: 100s of
             g/m2/year

            Temperate lakes: 1-
             20 g/m2/year

            Temperate streams:
             ~50 g/m2/year

				
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posted:5/3/2013
language:English
pages:16