Ecology B.Species Interactions 1.Intraspecific competition Ex – Competition for algae by sea urchins Ex – Competition for shells by hermit crabs 2.Interspecies competition

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

Ecology B.Species Interactions 3.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”

Ecology B.Species Interactions 3.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

Ecology B.Species Interactions 3.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”

Ecology B.Species Interactions 4.Symbiosis Relationship between host and symbiont a.Commensalism One partner benefits, other unaffected Ex – Barnacles living on whale b.Parasitism One partner benefits at expense of other Common in marine environment Ex – Tapeworm in whale c.Mutualism Both partners benefit Ex – Cleaner wrasses and shrimps on coral reefs Ex – Anemonefishes and anemones

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

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

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

Ecology C.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%)

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

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

Ecology C.Trophic Structures Decomposers – break down waste products

Marine Resources A.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

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 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

Marine Resources A.Fisheries 1.Clupeoid fishes

Marine Resources A.Fisheries

Marine Resources A.Fisheries 2.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

Marine Resources A.Fisheries

Marine Resources A.Fisheries

Marine Resources A.Fisheries 3.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)

Marine Resources A.Fisheries 3.Tunas

Marine Resources A.Fisheries

Marine Resources A.Fisheries 4.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

Marine Resources A.Fisheries 5.Fishery Yields

Marine Resources A.Fisheries 5.Fishery Yields Overfishing leads to 1)Stock depletion 2)Reduced catch rate 3)Capture of smaller individuals 4)Unsustainable harvest Biological – Can’t reproduce fast enough Economic – Can’t catch enough to make a profit

Marine Resources A.Fisheries 5.Fishery Yields