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Ocean Studies
Introduction to Oceanography
American Meteorological Society
Chapter 14
Ocean Stewardship
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Case in Point
– Oyster production in Chesapeake Bay peaked
in the 1880s and then declined.
– In the early 20th century, sailing vessels,
known as skipjacks were largely replaced by
powerboats, and the introduction of powered
winches permitted oysters to be harvested
from all depths.
• Oysters were overfished and oyster reefs were
destroyed in the process.
• In the early 20th century, commercial oyster
production slipped to historically low levels.
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Case in Point
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Sail powered oyster
dredges, known as
skipjacks.
Shells containing oyster spat raised by the
Oyster Recovery Partnership are bagged
and placed on pallets to grow before
being transplanted to a designated oyster
reef elsewhere in the Chesapeake Bay.
Case in Point
– Native oysters spawned and raised in hatcheries
were placed on oyster beds to grow.
• Few reached marketable size before dying from disease.
• Sterile Asian oysters were introduced; better adapted to living
in the muddy Chesapeake Bay waters than were the native
oysters
– Efforts to restore the oyster fishery in Chesapeake
Bay focus on physically rebuilding oyster reefs that
stand above the muddy bottom.
• Continue but are limited by cost and the scarcity of
appropriate materials for oyster attachment
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Ocean Stewardship
• Driving Question:
– How do we balance exploitation of fisheries
with efforts to preserve marine species and
ecosystems?
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Ocean Stewardship
• In this chapter, we examine:
– Examples of adverse human impacts on marine
fisheries and ecosystems
– Steps that are being taken to manage fisheries and
protect threatened marine species
– Ocean stewardship: action taken by society to protect
the ocean and its living and nonliving resources for
now and the future
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Stewardship of Ocean Life
– Stewardship of the ocean and its resources
involves responsibly managing all resources
to benefit present and future generations.
– Less than 5% of the ocean bottom has been
explored or mapped to the same resolution as
the surface of Earth’ neighboring planets,
Mars and Venus.
– For this reason, we often lack the basic
understandings needed to effectively manage
and protect marine living resources and their
associated ecosystems.
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Stewardship of Ocean Life
– In the United States, NOAA is the principal
government agency charged with stewardship
responsibilities for the nation’s marine environment
and living resources.
– Effective stewardship requires consideration of both
the biotic and abiotic components of marine
ecosystems to protect living organisms, their habitats,
and population sustaining interactions.
– One concept that is central to exercising wise
stewardship is sustainability.
• Requires effectively balancing environmental issues with
social and economic concerns, calls for intergenerational
equity in managing resources and the environment
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Fisheries and Sustainable
Exploitation
– Fisheries supply about 19% of all the animal protein
consumed by humans and the fishing industry
employs more than 200 million people, 95% of whom
live in developing nations.
– Coastal developing nations use traditional methods
(artisanal fisheries) and account for about half the
world’s marine fish production.
– In developed nations, fishers employ technologies
intended to increase the fish catch and a large
amount of commercial-fish production is processed
into fishmeal to feed pets and livestock, and for use in
fertilizers.
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Fisheries and Sustainable
Exploitation
• OVERFISHING
– Worldwide an estimated one-third of all exploited fish
stocks have collapsed; that is, their numbers have
declined to less than 10% of their historical maximum
population.
– Overfishing occurs when a fish species is taken at a
rate that exceeds the maximum catch that would
allow reproduction to replace the population.
• Recruitment overfishing: adult fish are taken in such great
numbers that too few survive to replenish the breeding stock
• Growth overfishing: fish that are taken too small, before the
animals have grown to a size that would produce the
maximum yield
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Fisheries and Sustainable
Exploitation
• OVERFISHING
– The first known human induced collapse of a marine
stock occurred about 3,000 years ago along the
Peruvian coast.
– In the years since the Industrial Revolution, a variety
of technological innovations enabled fishers from
developed nations to greatly increase the fish catch.
– Governments worldwide spend billions of dollars
annually subsidizing their commercial fishing industry.
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Fisheries and Sustainable
Exploitation
• OVERFISHING
– Government subsidies, greater fishing efficiency,
coupled with the growing demand for fish by the
soaring human population drove an increase in total
fish catch through the 1950s into the 1980s.
– The United Nations Food and Agriculture
Organization (FAO) reported that after many decades
of steady growth, the total annual wild fish catch
began to level off in the late 1980s.
– As fishers became more adept at taking fish in larger
numbers, stock collapses became more frequent
forcing fishery managers to impose quotas on
commercially desirable fish, limit fishing time at sea,
or close fisheries altogether.
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Fisheries and Sustainable
Exploitation
• OVERFISHING
– Overfishing has led to
the serial depletion of
fish populations as
each newly discovered
stock is fished out and
the fishing fleet moves
on to the next stock or
fishing area.
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Fisheries and Sustainable
Exploitation
• OVERFISHING
– As increasing fishing pressures cause
populations of top predators to decline,
organisms at progressively lower trophic
levels begin to dominate food webs in marine
ecosystems.
• Initially may be accompanied by an increase in
total catch
• Greater total catch is short-lived as populations of
the competitors of the top predators increase
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Fisheries and Sustainable
Exploitation
• MAXIMUM SUSTAINABLE YIELD
– To prevent overfishing of a fish stock, fishery
managers typically set catch quotas.
• Goal is to adhere to the maximum sustainable yield of the
fish stock; that is, limits are set on fish catches so that stocks
are maintained at a level that will ensure the long-term
viability of the target species
• A fishery is sustainable if it can be fished indefinitely at
reasonable levels while maintaining the ecosystem (function,
structure, and diversity) on which the fishery depends, and
the integrity of the habitat essential to the fish species.
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Fisheries and Sustainable
Exploitation
The maximum sustainable
yield of fish is based on a
model (A) that simulates the
growth of the population of
a fish species. The
maximum population, the
carrying capacity, is
determined by the
availability of resources in
the marine habitat. The
annual population growth
rate (B) peaks at some
intermediate population
size; this is the maximum
sustainable yield.
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Fisheries and Sustainable
Exploitation
• MAXIMUM SUSTAINABLE YIELD
– Maximum sustainable yield is based on a
model that simulates the population growth of
an exploited fish species.
– The carrying capacity is the maximum
population that can be sustained by the
resources of the marine habitat.
• In the case of fisheries, the maximum population
that would exist in the absence of commercial
fishing.
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Fisheries and Sustainable
Exploitation
• ECOLOGICALLY SUSTAINABLE YIELD
– Fish species are components of ecosystems
in which they interact with other organisms
and the physical/chemical environment.
• A decline in the population of a particular species
of fish may have a ripple effect on the entire
ecosystem, altering its biotic composition and
reducing its stability.
• Argues for a more holistic approach to fisheries
management
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Fisheries and Sustainable
Exploitation
• ECOLOGICALLY SUSTAINABLE YIELD
– Ecosystem approaches integrate ecological
principles, human systems, and goals of sustainability
for use in the management decision-making process.
– In 1993, the 24th Annual Report of the President’s
Council on Environmental Quality (CEQ)
recommended that the President issue a directive
establishing a national policy to encourage
sustainable development through ecosystem
management.
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Fisheries and Sustainable
Exploitation
• ECOLOGICALLY SUSTAINABLE YIELD
– Protection of fisheries requires a thorough
understanding of the entire ecosystem, not
just the targeted commercial or recreational
fish species.
• This understanding is the basis for achieving an
ecologically sustainable yield: the yield that a
marine ecosystem can sustain without undergoing
an undesirable change in state.
• New management concepts and associated
policies must take into account all the species that
interact with the targeted species and the habitats
they depend on.
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Fisheries and Sustainable
Exploitation
• BYCATCH
– Bycatch: fish and other marine animals that are
taken in addition to the target species
– Major threat to many endangered species, such as
sea turtles, dolphins, and other marine mammals
– Discarded, either dead or dying, because they cannot
be sold
• One-third of the annual commercial fish catch worldwide is
discarded for this reason
– Bycatch problem might be partially alleviated by
changing or rewriting governmental regulations to
relax quotas, permitting accidental catches to be
landed legally
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Fisheries and Sustainable
Exploitation
• RESTORING FISHERIES
– Few marine fisheries have been restored after
experiencing severe depletion.
– The goal of the ecosystem-based approach to
fisheries management is to maintain or re-establish
marine ecosystems that are home to fisheries.
• Require protection of seafloor habitats and expanding the
areas of the world ocean designated as protected areas,
called marine reserves, where fishing is prohibited
– Reducing the capacity of the global fishing fleet could
also help restore fisheries.
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Fisheries and Sustainable
Exploitation
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Map of the Channel Islands National
Marine Sanctuary
Fisheries and Sustainable
Exploitation
• HABITAT DESTRUCTION AND
RESTORATION
– Habitat destruction has also caused depletion
or destruction of major fish stocks.
• Benthic ecosystems and habitats have been
heavily damaged by steam-powered fishing boats
dragging heavy steel nets over the ocean bottom
to catch bottom-feeding fishes.
• Habitat destruction threatens oysters in coastal
and estuarine waters.
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Fisheries and Sustainable
Exploitation
A
(A) Volunteers help NOAA scientists prepare seagrass shoots for
planting. (B) Other volunteers help restore submerged seagrass near
Solomons Island in Chesapeake Bay
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B
Fisheries and Sustainable
Exploitation
• RECREATIONAL FISHERIES
– Involve large numbers of people who catch fish for
sport rather than for profit
– More than half the fishes caught by recreational
fishers are released alive; unfortunately many die due
to the stress of “catch and release”.
– Most recreational fishers prefer to fish near home;
hence, sport fish populations are most heavily fished
near major urban areas.
– Does not damage fish habitat as much as some
commercial fishing practices
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Protecting Endangered Marine
Species
– In 1973, the U.S. Endangered Species Act
became law providing for the protection of
endangered and threatened species.
• Species determined to be in imminent danger of
extinction throughout a significant portion of their
range are listed as endangered.
• Species are listed as threatened if they are likely to
become endangered in the foreseeable future.
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Protecting Endangered Marine
Species
• SEA TURTLES
– Seven species of sea turtles are
recognized worldwide.
• All are listed as either endangered
or threatened.
– Many human activities threaten sea turtle
population:
• commercial harvesting of adult turtles and the
poaching of eggs from nests
• development projects along beaches used by
turtles to nest
• bycatch in commercial fishing nets
• collisions with ships
• ingestion of plastic litter
• marine pollution
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Protecting Endangered Marine
Species
• SEA TURTLES
– The population of all sea turtles declined
nearly 90% between 1980 and 2000.
– There are several ways in which the threats to
sea turtles by commercial fishing can be
reduced:
• Special trap door in fishing nets that trawl the sea
floor
• Reducing the time a trawl net remains on the
bottom
• Declare areas with high seasonal populations of
turtles off limits to fishing at these times
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Protecting Endangered Marine
Species
• WHALES
– Hunting whales began early in human history.
– Whalers focused on a single species until its numbers
were so reduced that they had to hunt another
species.
– In 1982, to protect the world’s remaining whale
stocks, the International Whaling Commission (IWC)
declared a moratorium on commercial whaling to take
effect in 1986.
– Even after decades of protection, many whale stock
populations have still not rebounded to their original
numbers.
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Protecting Endangered Marine
Species
• WHALES
– Among endangered whales are the North Atlantic
right whale, blue, and bowhead whales.
Populations of
humpback whales
have recovered after
being listed
on the endangered
species list
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Protecting Endangered Marine
Species
• WATER BIRDS
– Restoration of some water-bird populations is among
the few successes resulting from environmental
policies and regulations in the late 20th century.
– Commercial fishers often killed pelicans by raiding
their nests because they were thought to be
voracious predators of commercially valuable fish
stocks.
• After 1940 their numbers were further reduced by the
widespread use of DDT and other persistent organic
pesticides.
• Began recovering after 1972 when the U.S. Environmental
Protection Agency banned the manufacture and use of DDT
• Removed from the endangered species list by 1985
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Protecting Endangered Marine
Species
• WATER BIRDS
– The history of North
American ospreys during
the 20th century was similar
to that of the brown
pelican.
– Osprey populations were
decimated by the egg
thinning caused by DDT
accumulation in their
tissues.
• 1972 ban on DDT greatly
aided their recovery
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Mariculture
– Mariculture (or marine aquaculture),
industrial farming of fish and shellfish in the
ocean is a growing industry worldwide.
• Dominate retail markets for many varieties of fish
and shellfish farmed fish
• Simplest mariculture operations involve filterfeeding mollusks (i.e., mussels, oysters and clams)
• Fish farms can add to water pollution problems.
• Salmon farms affect wild salmon and may be
responsible for reducing native salmon populations
in areas where the farms are located.
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Mariculture
Cobia at a Puerto Rican offshore mariculture
facility. Mariculture refers to the farming of fish
and shellfish in the ocean.
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Marine Exotic Species
– Animals and plants introduced into ecosystems,
usually by humans
• Some introductions are intentional (new organisms used for
mariculture) whereas others are unintentional (transported in
ships’ ballast waters).
• In most cases the introduced organisms do not survive
because they are not well adapted to the physical or
chemical conditions of their new environment or they are
unable to compete in the new ecosystem.
• Sometimes an exotic species finds its new environment to be
favorable; lacking competitors or diseases, their population
expands rapidly.
– Example: Asian carp, a large fast-growing fish imported from
China to the southern United States by fish farmers
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Marine Exotic Species
– New exotic organisms may also result from subtle
exchanges of genetic materials.
• Tall marsh grass (Phragmites) commonly found in the midAtlantic salt marshes has become a widespread and invasive
species that crowds out other types of marine grasses.
– Exotic marine organisms can also cause health
problems among humans.
• In 1993, a new strain of bacteria, native to Bangladesh and
India, appeared in Peru’s coastal waters and later spread
throughout Central and South America.
• Carried by coastal plankton
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Conclusions
– Overfishing forced imposition of quotas and the
closure of some fisheries but not before some species
came to the brink of extinction.
– Overfishing and its associated problems (e.g., habitat
destruction, bycatch) spurred fisheries managers to
reassess their management schemes.
– Move is to shift from the traditional method of
managing fisheries for maximum sustainable yield to
a more holistic, ecologically based approach that
emphasizes the sustainability of the marine
ecosystem that is home to the fishery.
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