Transcript Chapter 13

Chapter 13
Harvesting
Living Marine
Resources
Most of the world ocean is
intensively exploited for
fishing, recreation, military
purposes, commercial
shipping, dumping of waste
materials, and extraction of
gas, oil, and other mineral
resources.
Copyright © 2004 Jones and Bartlett Publishers
Chapter 13
A Brief Survey of Marine Food
Species
•The raw material of the fishing industry
includes:
– bony and cartilaginous finfish
– shellfish
– a variety of other aquatic organisms
Chapter 13
A Brief Survey of Marine Food
Species
Chapter 13
A Brief Survey of Marine Food
Species
•Clupeoid fishes account for about one third of
the world’s total commercial catch. Clupeoid
fishes are found in shallow coastal waters and
in upwelling regions.
•Cod, pollack, hake, and other gadoid fishes,
redfish, bass, sea perch, and other
miscellaneous coastal rockfishes, and tuna are
also important commercial targets.
•Bottom fishes and benthic invertebrates
account for 10–15% of the total global catch.
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Major Fishing Areas of the World
Ocean
•About 90% of the marine catch is taken
from continental shelves.
•Several major fishing areas are centered in
regions of upwelling, such as those along
the west coasts of Africa and North and
South America.
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A Perspective on Sources of
Seafoods
•Most of the seafood harvested are animals three
or four trophic levels above the primary producers.
•In contrast to land, more animals than plants are
harvested on land.
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A Perspective on Sources of
Seafoods
•The fish meal fraction had increased to about
40% of the world catch.
•We are currently overharvesting most
commercially important fish populations.
•As a result, only 1–2% of the food consumed by
the world human population came from the sea.
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Fishing Down the Food Chain
•By fishing one trophic level down, a 5- to 10- fold
increase could be harvested because one trophic
level (and its associated energy loss) would be
eliminated.
•However, harvesting near the base of a food web
often deny larger predators adequate prey, and
their populations suffer even though they are not
directly targeted by commercial fisheries.
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Mariculture
•Mariculture is the practice of using
agricultural techniques to raise marine
animals and plants
•Mariculture presently contributes less than
20% of our total marine food production.
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Mariculture
•Estuaries, salt marshes, and other
productive coastal habitats are preferred for
cultivating marine species, yet for each fish
pond installed, a portion of the native
populations are displaced or denied access
to these productive coastal waters, which
often serve as essential nursery areas.
The Problems of
Overexploitation
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•Numerous examples of overfished stocks
can be found in most segments of the
fishing industry:
– Cod of the N. Atlantic Ocean
– Anchoveta of the S. Pacific Ocean
The Problems of
Overexploitation
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•North Atlantic Cod
– Among the first to be taken by factory trawlers
(rather than by hand-lines for individual fish).
– When the population diminished and catches
declined, U.S. and Canadian regulatory
agencies closed nearly all cod fisheries in their
waters in 2003.
The Problems of
Overexploitation
Chapter 13
•North
Atlantic
Cod
Fig. 13.10 The dramatic decline in Northwestern Atlantic cod
harvests, 1970-2000. Data complied from UNFAO statistics.
The Problems of
Overexploitation
Chapter 13
•Peruvian Anchoveta
– The Peruvian anchoveta has become a classic
example of the consequences of intense
overfishing.
The Problems of
Overexploitation
Chapter 13
•Peruvian
Anchoveta
Fig. 13.11 Changes in the anchoveta catch and the guano bird
populations along the northwest coast of South America. Adapted from Muck
1989 and UNFAO statistics.
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The Tragedy of the Commons
•Fishing is too often considered a right
without attendant responsibilities.
•Oceanic species exist outside the
jurisdictional limits of all nations and
therefore are open to access by any nation.
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The Tragedy of the Commons
•Unrestricted fishing activities remove a
valuable commodity from a common resource
pool, and all people share the cost of losing
the fish, the great whales, and the other
marine animals that have nearly disappeared
because of overfishing.
•Yet the short-term profits derived from
overfishing are not similarly shared.
•This is Hardin’s concept of the “tragedy of
the commons.”
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International Regulation of
Fisheries
•Concerned nations have created a variety
of multinational and international regulatory
commissions for the purpose of governing
the management and harvest of regional
fish populations.
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International Regulation of
Fisheries
•Common strategies for management include:
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setting quotas on the amount of fish harvested
establishing seasons and minimum size limits
defining acceptable gear such as net mesh sizes
limiting the number of boats that are allowed to
participate in a fishery.
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International Regulation of
Fisheries
•In 1976, the United States passed the Fisheries
Conservation and Management Act, which claimed exclusive
jurisdiction over natural resources (including fishing),
scientific research, and environmental preservation in an EEZ
extending from shore 200 miles to sea.
•Other nations followed suit with the UN Law of the Sea
Treaty.
•This has dramatically changed the concept of open access
for most of the world’s continental shelves, coastal upwelling
areas, and major fisheries.
International Regulation of
Fisheries
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Fig. 13.12 Worldwide extent of the 200-mile Exclusive Economic
Zones sanctioned by the United Nations LOS Treaty.
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Marine Ornamentals
•Keeping personal marine aquaria supports
a trade that may be worth as much as $330
million annually.
•Unfortunately, destructive collection
techniques, overexploitation of some
species, and careless handling and transport
all undermine potential benefits of the trade.
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Marine Ornamentals
•Fisheries for marine ornamentals need to
be managed to ensure sustainable use and
application of proper regulations to decrease
conflict with other user groups (such as
sport divers).
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Sealing and Whaling
•Pinnipeds and whales have long been
targets of commercial harvesting for their
meat, oil, and skins with dense insulating
fur.
Chapter 13
Sealing and Whaling
•Pinnipeds
– The gregarious nature and relatively poor
terrestrial locomotion of pinnipeds make them
easy targets for sealers.
– As predators near the tops of their food webs,
the reduction of the their prey species by
human fishers can have a large negative effect
on their survival.
Sealing and Whaling
Chapter 13
•Pinnipeds
(a)
Fig. 13.13 Steller sea lion rookery beach photographed on the
same day of the year in (a) 1969 and (b) 1987.
(b)
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Sealing and Whaling
•Baleen Whales
– In the 18th and 19th centuries, whales
became major items of commerce as
demand for their oil grew and whaling as an
industry grew into a profitable commercial
enterprise.
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Sealing and Whaling
• Baleen Whales
– Aided by cannon-fired harpoons equipped
with explosive heads and pelagic factory
ships fitted with stern ramps to haul whale
carcasses aboard for processing, the kill of
large rorquals rose dramatically, and
several species were pushed to the edge of
extinction.
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Sealing and Whaling
•Baleen Whales
Fig. 13.14 Harvests of blue, fin, sei, and minke whales in the
Antarctic, 1920-2000. Data complied from UNFAO statistics.
Chapter 13
Sealing and Whaling
•Baleen Whales
– In 1948, 20 whaling nations established the
IWC to oversee the utilization and conservation
of the world’s whale resources. Unfortunately,
the IWC has neither inspection nor
enforcement powers.
Concluding Thoughts:
Developing a Sense of
Stewardship
•The world ocean provides food,
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transportation, and recreation while
absorbing the effluvia of human societies.
•Our continued wise use of the seas for
these purposes depends on a better
understanding of the consequences of our
intrusion on the workings of marine
ecosystems.
I am only one, but I am one
I cannot do everything, but I can
do something
I will not let what I cannot do
interfere with what I can