Transcript Aquatic Food Production Systems 4.3

Aquatic Food
Production Systems
4.3
Applications and Skills
• Discuss with reference to a case study
the controversial harvesting of a
named species
• Evaluate strategies that can be used to
avoid unsustainable fishing
• Explain the potential value of
aquaculture for providing food for
future generations
• Discuss a case study that demonstrates
the impact of aquaculture
Marine Ecosystems
• Marine
ecosystems
include:
o
o
o
o
o
o
Oceans
Mangroves
Estuaries
Lagoons
Coral reefs
Deep ocean floor
• Half of marine
productivity is in
coastal regions
above the
continental shelf
• Continental shelf
is an extension of
continents and
creates shallow
water
Marine Ecosystems
• Shallow water from continental shelves
are important:
o 50% of oceanic productivity but 15% of its total area
o Upwellings bring nutrient rich water up to the continental
shelf
o Light reaches shallow areas which helps photosynthesis
o Counties can use to exploit and harvest
• Deep ocean is not as productive (less light)
Marine Ecosystems
• The UN Convention on the Laws of the Sea
(UNCLOS) in 1982 designated continental
shelves as belonging to the country from
which they extend
• Also designated 370 km limit from the low
water mark of the shore as exclusive
economic zone belonging to the country
Marine
Ecosystems
• Outside these boundaries
are international waters
which no country controls
• Creates huge implications:
o
o
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Who fishes there?
Who controls them?
Who cleans up pollution problems?
Tragedy of the commons......
Marine Ecosystems
Marine Ecosystems
• Phytoplankton: single celled photosynthetic
organisms that are the most important
producer in the oceans
o Responsible for 99% of primary productivity
• Zooplankton: single celled animals that eat
phytoplankton and their waste (DOM)
• These organisms support
the complex food web of
the oceans
• Both float in the water
Marine
Food
Chain and
Webs
• Phytoplankton
and zooplankton
help to support
a complex
interconnected
set of marine
food webs
Marine Ecosystems
• Marine organisms can be classified as:
o Benthic –living on or in the sea bed (Benthos)
o Pelagic –living surrounded by water from above
the sea to the surface
Fisheries
• Fishery: exists when fish are harvested
in some way. Includes capture of wild
fish and aquaculture or fish farmin
• Aquaculture: the farming of aquatic
organisms in both coastal and inland
areas involving interventions in the
rearing process
Fisheries
• About 90% of fishery
activity is in oceans
and 10% in FW
• Include oysters,
mussels squid and
molluscs, eels, tuna,
etc
Methods of Fishing
• Some commercial fishing methods are not
sustainable and are very environmentally
damaging
o Dredging: drags a metal bag across the ocean floor.
Captures everything in path
o Gillnets: a curtain of netting is placed in the water with
holes large enough for fish to get head but not body
through. Large rates of bycatch
o Trawling: drags a net through the water behind a boat.
Captures any organism in path
o Blast Fishing: using explosives to kill fish in area. Kills all
life in area and damages coral
Fisheries
• Up to 0.5 billion people’s livelihoods
• 3 billion people gain 20% of their protein from fish,
the rest ~15%
• Fish is a good source of lean protein (important)
• Per Food and Agriculture Organization (FAO): 70%
of the world’s fisheries are fully exploited, in
decline, seriously depleted, or too low to allow
recovery
• Global fish catch is no longer increasing even
with better technology
Fisheries
World Aquaculture
Production
Fisheries
Aquaculture
• Many people in MEDC’s are opting for
healthier protein (fish) than terrestrial animals
• Worldwide, avg person eats 20kg of fish and
8 kg of meat per year
Aquaculture
• As demand for fish has increased, the extra
fish comes from fish farms
• Wild caught fish have reached its limit even
with better technology to find fish
• Either the fish just are not present because of
exploitation or we cannot take more than
the sustainable yield (not enough with
increasing population
• We will now be eating more farmed fish
than wild caught fish
Aquaculture - Benefits
• Ways in which fish farming is becoming more
sustainable:
o Fishmeal formula includes more scraps that were
once waste
o Livestock and poultry waste substitute for fishmeal
o USDA has shown 8 species of carnivorous fish can
get the same nutrients without eating other fish
o China uses carp and catfish which grow in rice
paddies. These fish add nutrients to the water
which act as a fertilizer for the rice
Aquaculture - Impacts
• There are some issues associated with fish
farming:
o Fish that are higher up the food chain (salmon, tuna)
still require nutrients from fish lower on food chain
leading to depletion of other species
o Loss of habitat (mangroves) to create fish farms
o Pollution of water due to fish feed and medications
added to fish pens
o Increase spread of disease due to confinement in small
spaces
o Often involve genetically modified species which may
breed with wild fish if they escape
o Escaped species may increase competition with native
species
Collapse of Fisheries
Case Study: Pacific Salmon
• Live along the west coast of the US (California to
Alaska)
• Many species endangered due to overfishing and
loss of freshwater habitat (deforestation and
hydroelectric dams)
• Atlantic salmon farms are being established in the
Pacific waters of British Columbia and Chile using
net-cage aquiculture
• Currently most of the salmon product being sold in
the U.S. are farm-raised salmon raised in these
Pacific waters.
• Concerns over: escape and threat to wild Pacific
salmon populations, viral and bacterial infections,
parasitic sea lice, and high levels of chemicals due
to fish pellets being used as food
Case Study: Hilsa Fish in
Bangladesh
• Hilsa is the national fish of Bangladesh
• Anadromous like salmon – born in freshwater rivers,
spend adult life in ocean (Bay of Bengal), return to
rivers to spawn
• National dish, part of celebrations and culture of
country
• Overfished due to growing population
• Fishing methods non-commercial, pole and nets
• Attempting to farm in ponds and among rice
paddies but difficulty with fertilizing eggs
• Government has banned export of fish
•
•
http://www.iied.org/bangladesh-protecting-hilsa-overfishing
http://en.prothom-alo.com/bangladesh/news/83225/Bangladesh-a-world-model-for-hilsaproduction
International Conflict Due to
Fishing Practices
• The ”cod wars” were a series of disputes between Britain
and Iceland running from the 1950s to the 1970s over the
rights to fish in Icelandic waters.
• Turbot (halibut) war between Canada and Spain in 1995
when Canada fired on a Spanish fishing boat and
chased it out of Canadian waters.
• Growing tension between India and Sri Lanka in 2012.
Over 100 Indian fisherman killed and 350 seriously injured
because of fishing along Sri Lankan coast
• This year China has increased their fishing fleet to over
2000 percent. In the past decade they have had
conflict for fishing in the waters of Indonesian, the
Philippines, Japanese, Korean and Russian.
•
•
http://www.nytimes.com/2012/09/05/world/asia/sri-lanka-and-india-battle-over-fishinggrounds.html?_r=0
http://www.worldpoliticsreview.com/articles/15112/fishing-wars-china-s-aggression-could-stokefuture-conflict
Tragedy of the Commons
• Conflict between individual need and the
common good of society
• If resource is seen as belonging to all, we
tend to overuse and exploit
• Oceans, lakes, and rivers tend to be good
examples of the tragedy of the commons
Maximum Sustainable Yield (MSY)
• Sustainable Yield: The amount of natural capital
that can be extracted each year without depleting
the stock to a point it is not replenishable.
• Maximum Sustainable Yield (MSY): The largest yield
or catch that can theoretically be taken from a
species’ stock without permanently depleting the
stock. (The maximum catch that will allow the
population to return to carrying capacity as quickly
as possible.)
Maximum Sustainable Yield (MSY)
• Generally MSY is
about ½ the
carrying capacity
of an organism
• Carrying Capacity
(K) is dependent
on:
o Reproductive Strategy
o Lifespan of organism
o Limiting factors in
ecosystem (resources
available)
Maximum Sustainable Yield (MSY)
• Calculating MSY is difficult as it is hard to determine the
actual carrying capacity of a population
• Must look at the annual growth in a population (births
and immigration) minus the annual decline in a
population (death and emigration)
• MSY is obtained if the population size will remain the
same from one year to the next