Download Chapter 10 Biological Productivity in the Ocean

Introduction to
Biological Oceanography
Biological Oceanography (3)
Classes of Marine Resources
How are marine resources classified?
 Physical resources
 Biological resources
 Marine energy resources
 Nonextractive resources
These resources can be further classified as renewable or nonrenewable.
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Salts and Minerals
What salts and minerals can be obtained from the ocean?
 Magnesium
 Sodium chloride
 Manganese nodules
 Phosphorite
 Metallic sulfides and muds
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Petroleum and Natural Gas
Oil and gas are often found together beneath impermeable caprock.
Drilling for oil offshore requires specialized equipment and is more
costly than drilling on land.
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Fresh Water
Fresh water is a valuable resource. Desalination of seawater can
provide a source of fresh water.
(above) An effective desalination method that requires little energy
input.
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Marine Energy
What methods of energy production could utilize the energy in
the ocean?
Energy generated by waves and currents
Ocean thermal energy conversion
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Marine Energy
A thermal energy conversion system first proposed in the 1880s.
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Biological Resources
Fish, crustaceans, and mollusks are the most valuable living
marine resources.
Fishing employs fifteen million people worldwide.
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Biological Resources
Some of the major types of commercially harvested fish, mollusks and
crustaceans.
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Living Resources
Marine finfish can be divided into the pelagic fish
which live in the water column and groundfish
which live on the sea floor.
• Most of the ocean is sparsely populated because of low nutrient
availability.
• Area of major fish production are the coastal waters and
regions of upwelling.
• Because they are economic to capture, major commercial fishes
are those which form large schools.
• The fishing industry uses sonar, scouting vessels, airplanes and
satellites to locate schools and then deploy the fishing fleets to
those areas.
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Living Resources
• Drift nets are controversial because they capture everything too
large to pass through the mesh of the net and needlessly kill
many organisms.
• The 1989 United Nations’ Convention for the Prohibition of Long Drift Nets
prohibited drift nets longer than 2.5 km, but compliance is largely voluntary and
impossible to enforce on the open sea.
• World ocean fish production appears to have leveled at between
80 and 90 million tons annually.
• Currently, the expense incurred in fishing exceeds the profit
from the sale of the fish and fishing industries only survive
through government subsidy.
A case study of overfishing: the Great Whales
Whaling
The whaling industry has pushed most of the dozen species of great whales to the
brink of extinction.
(above) These five species of whales are commercially extinct.
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Fishery Mismanagement
What are some key terms and ideas about fishery management?
Maximum sustainable yield - the maximum amount of any species that
can be harvested without affecting future yields
Overfished - a status assigned to fish stocks that have been harvested so
there is not enough breeding stock left for replenishment
Commercial extinction - the depletion of a species to the point where it
is no longer profitable to harvest
Bycatch - animals unintentionally killed when other species are being
harvested
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Fisheries management traditionally utilizes the
concept of MSY - Maximum Sustainable Yield
• Biological populations typically exhibit geometric growth to a
point where competition and density dependent factors slow
growth to a plateau
• The resultant growth curve of a population is a hysterisis, or ‘s’
shaped curve
• Point of maximum growth corresponds to rising slope.
• MSY models rely on the principle of only fishing the amount of
biomass that the population is capable of replacing on a yearly
basis
• Therefore, the Maximum Sustainable Yield of a population
corresponds to the point of maximal growth for the population
Where do MSY models fail?
• 70% of all commercial fish species are fully exploited
– Politics and scientific management do not mix!
– MSY does not allow for ‘natural’ catastrophes
– Inadequate data
• Many classic case-study ‘crashes’ exists
– Peruvian anchovy
– Pacific sardine
– North Atlantic Cod
• New management features include
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Precautionary principle
Reduced effort
Working lower down the food chain
Reducing by-catch
International cooperation
Other models (other than MSY) available to
Fisheries Managers
• Single species management examine the effects on the target
species alone - unrealistic?
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Yield per recruit
Age Cohort analysis
Statistical Catch-at-Age
Virtual population analysis (VPA)
• Multispecies methods examine biological and technical
interactions
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Multispecies surplus production
Multispecies yield per recruit
Multispecies VPA
Ecosystem modeling
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Living Resources
Mariculture is marine agriculture or fish farming of
finfish, shell fish and algae.
• Mariculture requires raising the organisms under favorable
conditions until they are large enough to be harvested for food.
• Currently, about one out of every four fish consumed spent part
of its life in mariculture and for some organisms the percentage
supplied by mariculture is even larger.
• For mariculture to be economically viable the species must be:
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Marketable.
Inexpensive to grow.
Trophically efficient.
At marketable size within 1 to 2 years.
Disease resistant.
Drugs
Researchers estimate that 10% of marine species may contain useful
medical compounds.
Acyclovir, the first antiviral compound approved for humans, is derived
from a Caribbean Sea sponge.
Pseudopterosins, a class of anti-inflammatory drugs, is derived from
marine species.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.
Nonextractive Resources
What are the main nonextractive resources of the ocean?
 transportation
 recreation
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The Law of the Sea
The Law of the Sea is an international agreement that governs the use
of the world ocean.
The United States Exclusive Economic Zone is a 10.3 million square
kilometer region of ocean on the coastal margin that the United States
unilaterally claims sovereign rights to and jurisdiction of.
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Law of the Sea
Several treaties regarding ownership and exploitation
of the marine resources have been ratified in the last
fifty years.
• President Truman extended U.S. control of the marine resources
from the shoreline to a depth of 100 fathoms (183 m).
• The 1958 and 1960 Geneva Conventions on the Law of the Sea
resulted in a treaty that placed the control of the sea bed, sea
bed resources and water of the continental shelf under the
country that owns the nearest land.
• The 1982 United Nations’ Draft Convention on the Law of the
Sea established Territorial waters and An Exclusive Economic
Zone (EEZ) that extends for 200 nautical miles offshore or to the
edge of the continental shelf, if that is farther.
• Exclusive economic zones contain about 40% of the ocean and
the high seas represent the remaining 60%.
The United States Exclusive Economic Zone
The United States Exclusive Economic Zone (EEZ) is shown in red.
Other EEZs are in blue.
© 2002 Brooks/Cole, a division of Thomson Learning, Inc.