Final: Lentic fish communities- Lake Mendota case study Flashcards
(22 cards)
Lake Mendota
Anthropogenic habitat change
Functional roles of fishes in ecosystems
Manipulation of fish assemblages
Unintended consequences of management
eutrophication
-nonpoint nutrient pollution
-most common impairment of surface waters in US excess inputs of phosphorus and nitrogen
phosphorus
polyps produce
nitrogen
polyps produce
nonpoint pollution
- inputs are the major
source of water pollution in U.S
-difficult to control –> biomanipulation
biomanipulation
Nonpoint sources difficult to
control
-top-down
increases habitat restoration
intensive stocking
harvest regulations
rooted aquatic plants
top-down vs bottom-up
Top-down: low water clarity –> planktivores abundant
northern pike
-adhesive egg
spawns on flooded vegitation
- sessile larve
adhesive eggs
-adheres on contact to substrate material or other eggs
piscivores
carnivorous animal that eats fish
-primary fish
EX: pickerel
sessile larvae
stays in one place
planktivores
-eat plankton and small organisms
EX: perch, cisco
zooplanktivory
acts of eating zooplankton
size-efficiency hypothesis
-Brooks and dodson (1965)
-plaktivores eat zooplankton so now more less effective grazers = more algea = affect algae biomass and clarity
zooplankters
-Grazers of algae
-bigger ones outcompete small
Daphnia
creates winterkill
low planktivore + high daphnia = clear waters pike
cisco
1987 cico summerkill
-coldwater fish
grazing
-less grazing = more algae
-more grazing = clearer water
surprises during biomanipulation
1987 Cisco summer kill
1990
-externial and internal nutrient loading,
summerkill
top layer = lots of algae
bottom= decomposition, depleted oxygen
outcome of the biomanipulation
Angler effort remained high
Piscivore biomass more than doubled
Planktivory decreased by >75%
Large Daphina remained dominant
More grazing reduced algae, clearer water
Rooted aquatic plants problematic
Brooks and Dodson paper
