Ecology

1. Ecology • Species Interactions • Intraspecific competition • Ex – Competition for algae by sea urchins • Ex – Competition for shells by hermit crabs • Interspecies competition

2. Ecology • Species Interactions • Interspecific competition – Competitive exclusion

3. Ecology • Species Interactions • Predation • 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 • Some prey have evolved defense mechanisms • 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”

4. Ecology • Species Interactions • Predation • 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

5. Ecology • Species Interactions • Predation • Some prey have evolved defense mechanisms • 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”

6. Ecology • Species Interactions • Symbiosis • Relationship between host and symbiont • Commensalism • One partner benefits, other unaffected • Ex – Barnacles living on whale • Parasitism • One partner benefits at expense of other • Common in marine environment • Ex – Tapeworm in whale • Mutualism • Both partners benefit • Ex – Cleaner wrasses and shrimps on coral reefs • Ex – Anemonefishes and anemones

7. Ecology • Trophic Structures • Energy and matter flow through ecosystems can be described through trophic relationships • Relationships between producers and consumers = food chain

8. Ecology • Trophic Structures • Food chains are often simplistic – alternative is a food web

9. Ecology • Trophic Structures • Food chains are often simplistic – alternative is a food web

10. Ecology • Trophic Structures • Energy transfer between trophic levels not 100% efficient • Matter consumed by metabolism • Energy released as heat • Matter released as waste • Transfer efficiency ~ 10% (5-20%)

11. Ecology • Trophic Structures • Energy transfer can be illustrated as pyramid of energy • Higher levels contain progressively less energy

12. Ecology • Trophic Structures • Energy transfer can be illustrated as pyramid of energy • Higher levels contain progressively less energy

13. Ecology • Trophic Structures • Decomposers – break down waste products

14. Marine Resources • Fisheries • 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

15. Marine Resources • Fisheries

16. Marine Resources • Fisheries

17. Marine Resources • Fisheries

18. Marine Resources • Fisheries

19. Marine Resources • Fisheries

20. Marine Resources • Fisheries • Clupeoid fishes • Herrings, sardines, anchovies, menhadens, shads • Feed on plankton (use gill rakers) • Form large schools over continental shelves and in upwelling zones • 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

21. Marine Resources • Fisheries • Clupeoid fishes

22. Marine Resources • Fisheries

23. Marine Resources • Fisheries • Cods and related fishes • Cods, pollock, haddock, hakes, whiting • Demersal and benthopelagic cold-water fishes • Caught with bottom trawls • Grand Banks (Newfoundland), Georges Bank (New England) and North Sea supported extensive cod fisheries until 1992, 1994, and 2001, respectively • Cod populations crashed; catches plummeted • Ex – North Sea catch • 1971 – 277,000 tonnes • 2001 – 59,000 tonnes

24. Marine Resources • Fisheries

25. Marine Resources • Fisheries

26. Marine Resources • Fisheries • Tunas • Skipjack, yellowfin, albacore, bigeye, bluefin • Primarily eaten in affluent countries • Can be very expensive (up to $40,000 for a choice bluefin in Tokyo) • Highly migratory species • 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)

27. Marine Resources • Fisheries • Tunas

28. Marine Resources • Fisheries

29. Marine Resources • Fisheries • Other species • 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 • Squid, octopus • Clams, oysters, scallops • Crabs, lobsters • Sea urchin, sea cucumber • Barnacles, jellyfish • Sea turtles, seals, whales

30. Marine Resources • Fisheries • Fishery Yields

31. Marine Resources • Fisheries • Fishery Yields • Overfishing leads to • Stock depletion • Reduced catch rate • Capture of smaller individuals • Unsustainable harvest • Biological – Can’t reproduce fast enough • Economic – Can’t catch enough to make a profit

32. Marine Resources • Fisheries • Fishery Yields