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Sustaining Aquatic Food Resources and Biodiversity

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Title: Sustaining Aquatic Food Resources and Biodiversity


1
Chapter 13
  • Sustaining Aquatic Food Resources and Biodiversity

2
Chapter Overview Questions
  • What do we know about aquatic biodiversity, and
    what is its economic and ecological importance?
  • How are human activities affecting aquatic
    biodiversity?
  • How can we protect and sustain marine
    biodiversity?
  • How can we manage and sustain the worlds marine
    fisheries?

3
Chapter Overview Questions (contd)
  • How can we protect, sustain, and restore
    wetlands?
  • How can we protect, sustain, and restore lakes,
    rivers, and freshwater fisheries?

4
Core Case Study A Biological Roller Coaster Ride
in Lake Victoria
  • Lake Victoria has lost their endemic fish species
    to large introduced predatory fish.

Figure 12-1
5
Core Case Study A Biological Roller Coaster Ride
in Lake Victoria
  • Reasons for Lake Victorias loss of biodiversity
  • Introduction of Nile perch.
  • Lake experienced algal blooms from nutrient
    runoff.
  • Invasion of water hyacinth has blocked sunlight
    and deprived oxygen.
  • Nile perch is in decline because it has eaten its
    own food supply.

6
AQUATIC BIODIVERSITY
  • We know fairly little about the biodiversity of
    the worlds marine and freshwater systems.
  • The greatest marine biodiversity occurs in coral
    reefs, estuaries and the deep ocean floor.
  • Biodiversity is higher near the coast and surface
    because of habitat and food source variety.
  • The worlds marine and freshwater systems provide
    important ecological and economic services.

7
HUMAN IMPACTS ON AQUATIC BIODIVERSITY
  • Human activities have destroyed, disrupted or
    degraded a large proportion of the worlds
    coastal, marine and freshwater ecosystems.
  • Approximately 20 of the world's coral reefs have
    been destroyed.
  • During the past 100 years, sea levels have risen
    10-25 centimeters.
  • We have destroyed more than 1/3 of the worlds
    mangrove forests for shipping lanes.

8
HUMAN IMPACTS ON AQUATIC BIODIVERSITY
  • Area of ocean before and after a trawler net,
    acting like a giant plow, scraped it.

Figure 12-2
9
HUMAN IMPACTS ON AQUATIC BIODIVERSITY
  • Harmful invasive species are an increasing threat
    to marine and freshwater biodiversity.
  • Bioinvaders are blamed for about 2/3 of fish
    extinctions in the U.S. between 1900-2000.
  • Almost half of the worlds people live on or near
    a coastal zone and 80 of ocean water pollution
    comes from land-based human activities.

10
Population Growth and Pollution
  • Each year plastic items dumped from ships and
    left as litter on beaches threaten marine life.

Figure 12-3
11
Overfishing and Extinction Gone Fishing, Fish
Gone
  • About 75 of the worlds commercially valuable
    marine fish species are over fished or fished
    near their sustainable limits.
  • Big fish are becoming scarce.
  • Smaller fish are next.
  • We throw away 30 of the fish we catch.
  • We needlessly kill sea mammals and birds.

12
Trawler fishing
Fish farming in cage
Spotter airplane
Sonar
Purse-seine fishing
Trawl flap
Trawl lines
Fish school
Trawl bag
Drift-net fishing
Long line fishing
Buoy
Float
Lines with hooks
Deep sea aquaculture cage
Fish caught by gills
Fig. 12-A, p. 255
13
Why is it Difficult to Protect Aquatic
Biodiversity?
  • Rapid increasing human impacts, the invisibility
    of problems, citizen unawareness, and lack of
    legal jurisdiction hinder protection of aquatic
    biodiversity.
  • Human ecological footprint is expanding.
  • Much of the damage to oceans is not visible to
    most people.
  • Many people incorrectly view the oceans as an
    inexhaustible resource.

14
PROTECTING AND SUSTAINING MARINE BIODIVERSITY
  • Laws, international treaties, and education can
    help reduce the premature extinction of marine
    species.
  • Since 1989 the U.S. government has required
    offshore shrimp trawlers to use turtle exclusion
    devices.
  • Sea turtle tourism brings in almost three times
    as much money as the sale of turtle products.

15
PROTECTING AND SUSTAINING MARINE BIODIVERSITY
  • Six of the worlds seven major turtle species are
    threatened or endangered because o human
    activities.

Figure 12-4
16
Case Study The Florida Manatee and Water
Hyacinths
  • Manatee can eat unwanted Water Hyacinths.
  • Endangered due to
  • Habitat loss.
  • Entanglement from fishing lines and nets.
  • Hit by speed boats.
  • Stress from cold.
  • Low reproductive rate

Figure 12-B
17
Case Study Commercial Whaling
  • After many of the worlds whale species were
    overharvested, commercial whaling was banned in
    1960, but the ban may be overturned.

Figure 12-6
18
Case Study Commercial Whaling
  • Despite ban, Japan, Norway, and Iceland kill
    about 1,300 whales of certain species for
    scientific purposes.
  • Although meat is still sold commercially.

Figure 12-5
19
Toothed whales
Sperm whale with squid
Killer whale
Narwhal
Bottlenose dolphin
Baleen whales
Blue whale
Fin whale
Bowhead whale
Right whale
Sei whale
Humpback whale
Gray whale
Minke whale
Fig. 12-5, p. 258
20
How Would You Vote?
  • Should carefully controlled commercial whaling be
    resumed for species with populations of 1 million
    or more?
  • No. The hunting of whales is no longer necessary
    and simply encourages disrespect for these
    intelligent giants.
  • Yes. Some whale species have recovered and
    products from them are valuable resources for
    humans.

21
PROTECTING AND SUSTAINING MARINE BIODIVERSITY
  • Fully protected marine reserves make up less than
    0.3 of the worlds ocean area.
  • Studies show that fish populations double, size
    grows by almost a third, reproduction triples and
    species diversity increases by almost one fourth.
  • Some communities work together to develop
    integrated plans for managing their coastal areas.

22
Revamping Ocean Policy
  • Two recent studies called for an overhaul of U.S.
    ocean policy and management.
  • Develop unified national policy.
  • Double federal budget for ocean research.
  • Centralize the National Oceans Agency.
  • Set up network of marine reserves.
  • Reorient fisheries management towards ecosystem
    function.
  • Increase public awareness.

23
MANAGING AND SUSTAINING MARINE FISHERIES
  • There are a number of ways to manage marine
    fisheries more sustainably and protect marine
    biodiversity.
  • Some fishing communities regulate fish harvests
    on their own and others work with the government
    to regulate them.
  • Modern fisheries have weakened the ability of
    many coastal communities to regulate their own
    fisheries.

24
Solutions
Managing Fisheries
Fishery Regulations Set catch limits well below
the maximum sustainable yield Improve monitoring
and enforcement of regulations
Bycatch Use wide-meshed nets to allow escape of
smaller fish Use net escape devices for sea
birds and sea turtles Ban throwing edible and
marketable fish back into the sea
Economic Approaches Sharply reduce or eliminate
fishing subsidies Charge fees for harvesting
fish and shellfish from publicly owned offshore
waters Certify sustainable fisheries
Aquaculture Restrict coastal locations for fish
farms Control pollution more strictly Depend
more on herbivorous fish species
Protected Areas Establish no-fishing
areas Establish more marine protected
areas Rely more on integrated coastal management
Nonnative Invasions Kill organisms in ship
ballast water Filter organisms from ship ballast
water Dump ballast water far at sea and replace
with deep-sea water
Consumer Information Label sustainably harvested
fish Publicize overfished and threatened species
Fig. 12-7, p. 261
25
PROTECTING, SUSTAINING, AND RESTORING WETLANDS
  • Requiring government permits for filling or
    destroying U.S. wetlands has slowed their loss,
    but attempts to weaken this protection continue.

Figure 12-8
26
Solutions
Protecting Wetlands
Legally protect existing wetlands Steer
development away from existing wetlands Use
mitigation banking only as a last resort Require
creation and evaluation of a new wetland before
destroying an existing wetland Restore degraded
wetlands Try to prevent and control invasions by
nonnative species
Fig. 12-9, p. 264
27
Case Study Restoring the Florida Everglades
  • The worlds largest ecological restoration
    project involves trying to undo some of the
    damage inflicted on the Everglades by human
    activities.
  • 90 of parks wading birds have vanished.
  • Other vertebrate populations down 75-95.
  • Large volumes of water that once flowed through
    the park have been diverted for crops and cities.
  • Runoff has caused noxious algal blooms.

28
Restoring the Florida Everglades
  • The project has been attempting to restore the
    Everglades and Florida water supplies.

Figure 12-10
29
PROTECTING, SUSTAINING, AND RESTORING LAKES AND
RIVERS
  • Lakes are difficult to manage and are vulnerable
    to planned or unplanned introductions of
    nonnative species.
  • For decades, invasions by nonnative species have
    caused major ecological and economic damage to
    North Americas Great lakes.
  • Sea lamprey, zebra mussel, quagga mussel, Asian
    carp.

30
PROTECTING, SUSTAINING, AND RESTORING LAKES AND
RIVERS
  • Dams can provide many human benefits but can also
    disrupt some of the ecological services that
    rivers provide.
  • 119 dams on Columbia River have sharply reduced
    (94 drop) populations of wild salmon.
  • U.S. government has spent 3 billion in
    unsuccessful efforts to save the salmon.
  • Removing hydroelectric dams will restore native
    spawning grounds.

31
How Would You Vote?
  • Should federal efforts to rebuild wild salmon
    populations in the Columbia River Basin be
    abandoned?
  • a. No. Restoring salmon populations is critical
    for the environmental health of the river and
    surrounding forests.
  • b. Yes. The restoration program would create
    unnecessary and severe economic hardships for
    local residents.

32
PROTECTING, SUSTAINING, AND RESTORING LAKES AND
RIVERS
  • We can help sustain freshwater fisheries by
    building and protecting populations of desirable
    species, preventing over-fishing, and decreasing
    populations of less desirable species.
  • A federal law helps protect a tiny fraction of
    U.S. wild and scenic rivers from dams and other
    forms of development.
  • National Wild and Scenic Rivers Act (1968).

33
Natural Capital
Ecological Services of Rivers
  • Deliver nutrients to sea to help sustain
    coastal fisheries
  • Deposit silt that maintains deltas
  • Purify water
  • Renew and renourish wetlands
  • Provide habitats for wildlife

Fig. 12-11, p. 267
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