Download Marine resources Marine Resources are Utilized For: Food From the

Marine Resources are Utilized
For:
Marine resources
•
•
•
•
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
Worldwide Commercial Catches
• 1950’
1950’s to presentpresent- there was a fivefive-fold
increase in fishing effort
• 1980’
1980’s to presentpresent- worldwide catches
relatively constant despite the increased
fishing effort
• Many of world’
world’s most important catches
are overexploited or exhausted (especially
in the Atlantic, Pacific and Mediterranean)
1
Major Fishing Areas
Worldwide
Marine Catch
and Mariculture
• 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
Optimal Yield and Overfishing
• SeaSea-life species are renewable resources
• However, for a fishery to last longlong-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
Exceeding Maximum
Sustainable Yield
• It is estimated that about 70% of marine fishes
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’
1950’s than they
are today
2
Exceeding Maximum
Sustainable Yield
• Swordfish
• Catches of these fish fell 70% between the
1960’
1960’s and the late 1990’
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 oneone-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
Ways to Manage a Fishery
• Limiting total catch and closing the fishery when the
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
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”
property”
United StatesStates- Sustainable
Fisheries Act
• Passed in 1996
• Requires federal fisheries managers to develop
plans to avoid overfishing, restore depleted
stocks and reduce byby-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
3
New Fisheries
Mariculture and Aquaculture
• New fisheries may be available by increasing
the use of byby-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
• Aquaculture is the application of farming techniques to
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 threethree-fold since 1990
• As an example, farmed fish account for 25% of shrimp
consumed each year
• Other “farmed”
farmed” species include milkfish, molluscs,
seaweed, salmon and Pacific threadfish
Commercial Mariculture Species
Geoduck farming
•
•
•
Mussel farming
plants geoduck “seed”
at a higher density than
what occurs in nature.
predator protection
devices (pvc tubes or
netting) around small
geoduck “seed” when
they are most
vulnerable to predation
by shrimp, crabs,
flatfish, and sea stars (in
the first 6 to 18 months
after planting).
A crop of geoducks may
take 6-8 years to reach
market size. After
harvest, an intertidal
area under an aquatic
farmers control may be
re-planted with geoduck
seed to begin a new
crop.
4
Oyster farming
Salmon net pen farming
•
Problems:
– Escapes
– Sedimentation
– Genetically
modified
Problems Associated with
Aquaculture/Mariculture
Aquaculture/Mariculture
• Disease and parasites can be high due to many organisms in close
proximity
• Different food requirements may be present at different life stages
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
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
NonNon-Living Resources
Harvested from the Marine
Environment
• NaCl
NonNon-Living Resources
Harvested from the Marine
Environment
• Oil and Gas
• Sand and gravel for the
construction industry
• Freshwater via
desalination process
NonNon-Living Resources
Harvested from the Marine
Environment
• Tidal energy
5