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Chapter 17
Lecture
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Chapter 17
Resources from the Sea
Marine Resources are Utilized
For:
• Food
• Products
• Materials
• Recreation
Food From the Sea
• What types of organisms are harvested?
– Finfish (about 90% of worldwide harvest)
– Shellfish
– Other species such as jellyfish, sea
cucumbers, polychaetes and seaweed
– While seafood represents only about 1% of
the food consumed each year, it represents
about 30% of total animal protein consumed
The Fisheries Industry
• 1950’s to present- there was a five-fold
increase in fishing effort
• 1980’s to present- worldwide catches
relatively constant despite the increased
fishing effort
• Many of world’s most important catches
are overexploited or exhausted (especially
in the Atlantic, Pacific and Mediterranean)
Worldwide Commercial Catches
Worldwide Marine Catch and
Mariculture
Major Fishing Areas
• Most located near coast over continental
shelf
• Easier to catch demersal species
• High primary production in these areas
means more species are present
• Ex: Grand Banks of Newfoundland, North
Sea and Bering Sea
Examples of Commercially
Important Fishes Around the
World
Major Food Species
• Clupeoid fishes
– Sardines, menhaden, shad and herrings
• How they are used:
– Eaten directly
– Fish flour (powder used as a dietary supplement
– Fish meal (ground fish used as protein supplement for
poultry, livestock and aquaculture
– Fish oil (used in manufacture of margarine,
cosmetics, paints, omega-3 fatty acids
Major Food Species
• Cods, haddock, hakes, pollock, whiting
• Demersal, cold water species
• Has been harvested for centuries
• Sold fresh and frozen
• Vital source of inexpensive protein in
many parts of the world
Cod Fishery of the Grand Banks
• Fishery peaked in the 1960’s then began
to decline
• Moratorium declared in 1992 to attempt to
save the fishery
• Closure caused high unemployment in
American and Canadian fishermen
• The fishery may never recover
• The cod is listed as endangered in that
area even today
Major Food Species
• Jacks, Mullets, Rockfishes and Mackerels
– Important in worldwide tonnage
– Cheap protein in some parts of the world
• In the United States, flounders and other
flatfish are important
• Salmon also remain important catch
Major Food Species
• Tuna
– Caught in open water
– These fish command high prices
– They are caught on long lines or in gillnets
– Fishing boats are equipped with freezers so
they can stay at sea longer
Major Food Species
• Molluscs
– Second most valuable catch after finfish
– Squids, cuttlefish, and octopus are particularly
important in the Far East
– Clams, oysters, mussels, scallops and
abalones are important worldwide
Major Food Species
• Crustaceans
– Prized worldwide
– Command high prices
– Shrimp, lobster, crab
Other Harvested Marine Life
• These species contribute little to the worldwide
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catch
Sea weeds, jellyfish and sea urchins harvested in
Far East, especially Japan
Gooseneck barnacles are harvested in Spain
Polychaete worms are harvested in South Pacific
Sea turtles and their eggs are harvested and
eaten even where they are protected by law
Seals and whales are still eaten in some cultures
despite laws to protect them
Optimal Yield and Overfishing
• Sea-life species are renewable resources
• However, for a fishery to last long-term, it
must be fished in a sustainable way
• The sustainable yield is the amount that
can be caught and just maintain a
constant population size
• Maximum sustainable yield is the highest
catch that can be maintained year after
year without affecting the stock
Exceeding Maximum Sustainable
Yield
• If catches fall despite increased fishing
effort, overfishing has occurred
• Market forces often cause this to happen
• If other fishermen are making money,
other fishermen will be attracted to the
fishery and cause overfishing to occur
Exceeding Maximum Sustainable
Yield
• It is estimated that about 70% of marine fishes
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are overfished
This is especially true for large species like tuna,
swordfish and sharks
In many of these species, the fish that are
harvested today are about half the size of those
harvested 20 years ago
Ex: Bigeye tuna were two times as heavy and
eight times more abundant in 1950’s than they
are today
Exceeding Maximum Sustainable
Yield
• Swordfish
• Catches of these fish fell 70% between
the 1960’s and the late 1990’s
• A campaign to reduce consumption of
these fish was successful
• Numbers of the fish are recovering
Other Dangers to Fisheries
• Habitat destruction
– Critical breeding grounds like seagrass beds,
estuaries and mangroves are destroyed each
year
– This is especially detrimental since 75% of
commercially important species use estuarine
areas as nursery areas
• Trawls used in fisheries also damage the
ocean floor which is detrimental to
demersal species
Collapse of a Fishery
• A fishery is regarded as collapsed if
numbers fall to 10% of historic highs
• It is estimated that one-third of fisheries
are already collapsed
• A 2006 study indicates that all major
fisheries will collapse by 2050 if protective
measure are not taken to better manage
and protect these resources
Managing the Resources
• Management can be difficult for many
reasons:
– Maximum sustainable yield is difficult to
calculate
– Harvested species may compete with other
species and fishing pressure may affect
competitive balance
– Real fisheries are more complex than models
– High seas are “common property”
Ways to Manage a Fishery
• Limiting total catch and closing the fishery when the
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catch is reached
Limiting length of fishing season
Limiting areas open for fishing (to include marine
reserves)
Limiting number of boats permitted to fish
Limiting gear size or gear type
Limiting size of fish caught
Limiting catches per boat
Limiting fishing methods
United States- Sustainable
Fisheries Act
• Passed in 1996
• Requires federal fisheries managers to develop
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plans to avoid overfishing, restore depleted
stocks and reduce by-catch (species caught
incidentally while fishing for a target species)
US fishermen must abide by rules as well as
foreign fishermen with valid permits
In 2003, the Pews Ocean Commission calls for
management of ecosystems as well
New Fisheries
• New fisheries may be available by increasing the
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use of by-catch
However, consumer tastes are fickle and these
species may not be appealing to consumers
Some species may be able to be used in the
manufacture of imitation crab (as pollocks are
currently)
Other untapped potential fisheries – squid, flying
fish and lanternfish
Mariculture and Aquaculture
• Aquaculture is the application of farming techniques to
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the growth and harvesting of aquatic organisms
The term mariculture applies specifically to marine
organisms
The column of marine organisms produced through
mariculture has risen three-fold since 1990
As an example, farmed fish account for 25% of shrimp
consumed each year
Other “farmed” species include milkfish, molluscs,
seaweed, salmon and Pacific threadfish
Commercial Mariculture Species
Problems Associated with
Aquaculture/Mariculture
• Disease and parasites can be high due to many organisms in close
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proximity
Different food requirements may be present at different life stages
Species that require open water cannot be raised this way
Maintaining water quality may be difficult
If farmed species escape, they may breed with wild stocks and
dilute genome of wild population
Pollution from farm ponds can leak into nearby waters
In some areas of the world, mangroves and other estuarine
communities are destroyed to create farm ponds
Marine Life as Items of
Commerce and Recreation
• Other items harvested for reasons other
than direct consumption:
– Mangroves – for timber and charcoal
– Pearls, shells, coral and sea turtle shells for
jewelry
– Some species harvested for their chemical
compounds that are used as “marine natural
products”
Marine Life as Items of
Commerce and Recreation
• Amateur anglers – in general, marine
resources caught by recreational anglers is
only about 30% of the amount caught by
commercial fishermen
• However, for some species, the number of
individuals caught each year may be solely
from recreational anglers
• Other species are harvested each year for
the aquarium trade
Non-Living Resources Harvested
from the Marine Environment
• Oil and Gas
• Sand and gravel for the construction
industry
• Freshwater via desalination process
Non-Living Resources Harvested
from the Marine Environment
• NaCl
Non-Living Resources Harvested
from the Marine Environment
• Tidal energy
Non-Living Resources Harvested
from the Marine Environment
• Polymetallic nodules – contain
manganese, nickel, copper and cobalt