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Ecology
B.
Species Interactions
1.
Intraspecific competition
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2.
Ex – Competition for algae by sea urchins
Ex – Competition for shells by hermit crabs
Interspecies competition
Ecology
B.
Species Interactions
2.
Interspecific competition – Competitive exclusion
Ecology
B.
Species Interactions
3.
Predation
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Natural selection favors increased predation efficiency
Predators can control prey populations (Top-down)
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Reduce competition/competitive exclusion
Prey can control predator populations (Bottom-up)
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Prey = food
Some prey have evolved defense mechanisms
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Ex – Spines in plankton
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Ex – Poisonous chemicals in algae and mollusks
Some defenses are inducible
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Ex – Barnacles grow upright when predatory snails absent and
horizontally when snails present
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Ex – Algae produce more bad-tasting chemicals after being
damaged
Coevolution – Evolutionary “arms race”
Ecology
B.
Species Interactions
3.
Predation
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Natural selection favors increased predation efficiency
Predators can control prey populations (Top-down)
•
Reduce competition/competitive exclusion
Prey can control predator populations (Bottom-up)
•
Prey = food
Ecology
B.
Species Interactions
3.
Predation
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Some prey have evolved defense mechanisms
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Ex – Spines in plankton
•
Ex – Poisonous chemicals in algae and mollusks
Some defenses are inducible
•
Ex – Barnacles grow upright when predatory snails absent and
horizontally when snails present
•
Ex – Algae produce more bad-tasting chemicals after being
damaged
Coevolution – Evolutionary “arms race”
Ecology
B.
Species Interactions
4.
Symbiosis
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a.
b.
c.
Relationship between host and symbiont
Commensalism
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One partner benefits, other unaffected
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Ex – Barnacles living on whale
Parasitism
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One partner benefits at expense of other
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Common in marine environment
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Ex – Tapeworm in whale
Mutualism
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Both partners benefit
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Ex – Cleaner wrasses and shrimps on coral reefs
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Ex – Anemonefishes and anemones
Ecology
C.
Trophic Structures
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Energy and matter flow through ecosystems can be
described through trophic relationships
Relationships between producers and consumers = food
chain
Ecology
C.
Trophic Structures
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Food chains are often simplistic – alternative is a food web
Ecology
C.
Trophic Structures
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Food chains are often simplistic – alternative is a food web
Ecology
C.
Trophic Structures
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Energy transfer between trophic levels not 100% efficient
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Matter consumed by metabolism
Energy released as heat
Matter released as waste
Transfer efficiency ~ 10% (5-20%)
Ecology
C.
Trophic Structures
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Energy transfer can be illustrated as pyramid of energy
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Higher levels contain progressively less energy
Ecology
C.
Trophic Structures
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Energy transfer can be illustrated as pyramid of energy
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Higher levels contain progressively less energy
Ecology
C.
Trophic Structures
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Decomposers – break down waste products
Marine Resources
A.
Fisheries
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Seafood is ~1% of all food eaten worldwide
Seafood especially important in poor coastal nations with
low protein availability
World seafood catch stabilized by late 1980s
Marine Resources
A.
Fisheries
Marine Resources
A.
Fisheries
Marine Resources
A.
Fisheries
Marine Resources
A.
Fisheries
Marine Resources
A.
Fisheries
Marine Resources
A.
Fisheries
1.
Clupeoid fishes
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Herrings, sardines, anchovies, menhadens, shads
Feed on plankton (use gill rakers)
Form large schools over continental shelves and in upwelling zones
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Caught with purse seines
Industrial fisheries
- Fish meal (protein supplement in animal feed)
- Fish oil (margarine, cosmetics, paint)
- Fish flour (protein supplement for humans)
- Fertilizers
- Pet food
Marine Resources
A.
Fisheries
1.
Clupeoid fishes
Marine Resources
A.
Fisheries
Marine Resources
A.
Fisheries
2.
Cods and related fishes
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Cods, pollock, haddock, hakes, whiting
Demersal and benthopelagic cold-water fishes
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Caught with bottom trawls
Grand Banks (Newfoundland), Georges Bank (New England) and
North Sea supported extensive cod fisheries until 1992, 1994, and
2001, respectively
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Cod populations crashed; catches plummeted
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Ex – North Sea catch
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1971 – 277,000 tonnes
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2001 – 59,000 tonnes
Marine Resources
A.
Fisheries
Marine Resources
A.
Fisheries
Marine Resources
A.
Fisheries
3.
Tunas
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Skipjack, yellowfin, albacore, bigeye, bluefin
Primarily eaten in affluent countries
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Can be very expensive (up to $40,000 for a choice bluefin in
Tokyo)
Highly migratory species
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Caught with purse seines, longlines, gill nets, rod and reel
Often associate with floating objects, dolphin schools
Juveniles caught in purse seines may be finished in net pens
(aquaculture)
Marine Resources
A.
Fisheries
3.
Tunas
Marine Resources
A.
Fisheries
Marine Resources
A.
Fisheries
4.
Other species
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Flatfishes, rockfishes, mackerels, salmon
Mostly coastal
Threatened by coastal pollution, damming of rivers (salmon),
overfishing
Flatfishes and rockfishes harvested extensively in US
Salmon farmed heavily in Canada, Chile
Non-finfish
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Squid, octopus
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Clams, oysters, scallops
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Crabs, lobsters
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Sea urchin, sea cucumber
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Barnacles, jellyfish
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Sea turtles, seals, whales
Marine Resources
A.
Fisheries
5.
Fishery Yields
Marine Resources
A.
Fisheries
5.
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Fishery Yields
Overfishing leads to
1)
2)
3)
4)
Stock depletion
Reduced catch rate
Capture of smaller individuals
Unsustainable harvest
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Biological – Can’t reproduce fast enough
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Economic – Can’t catch enough to make a profit
Marine Resources
A.
Fisheries
5.
Fishery Yields