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Methods, Pro’s and Con’s
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History• Fish are a vital component of the human diet -
nearly half the world’s population gets the majority of its protein from seafood
• As population increases, so does demand for seafood…
• But Many species - perhaps 70% or more - have been fished to their sustainable limits or beyond.
• Fish stocks are declining
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Why are our fish stocks declining?• Overfishing:
– Bigger fishing vessels
– Better technology to find fish
– Better nets– Higher
demand– Lag time in
population drop FAO State of World Fisheries and Aquaculture (SOFIA) – 2006
http://www.fao.org/DOCREP/007/y5600e/y5600e00.htm
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Question
What do we do?
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The answer: Aquaculture?• Proponents of fish farming say that the
industry not only supplies an important food resource, it also benefits wild stocks by reducing fishing pressures.
• However, Many fishermen and environmentalists disagree– claim that aquaculture can degrade the
habitat, health, and genetic vigor of wild species
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Salmon DebateFarm-raised Salmon Wild Salmon
Survival rate from egg to adult of 80-90%
Concentrated waste cause algal blooms and low oxygen ‘dead zones’
Higher levels of pollutants in tissues
Less expensive and more widely available to consumers
Color from dyes, feed antibiotics, fewer essential fatty acids and oils
Survival rate from egg to adult of 1-2%
Declining wild populations due to overfishing and habitat degradation
Live and dead fish important part of stream and ocean food chains
Seabirds and marine mammals caught and killed during fishing activities
No dyes, no antibitoics, healthier
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Open net pens or cages• Anchored in offshore
coastal areas– Salmon, tuna
• Pro’s: – Cheap– no by-catch– does not deplete wild stocks
• Con’s:– Waste passes to
environment– Escapees– Disease & parasites
http://www.ambhanoi.um.dk/NR/rdonlyres/92ADABED-4F6A-4F6A-A04D-2A83242C1687/0/aquaculture3.jpg
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Ponds • Manmade ponds, recirculating seawater
– Shrimp, catfish, tilapia• Pro’s:
– Cheap– no by-catch– does not deplete wild stocks– Provides jobs
• Con’s:– Location of ponds can destroy
important habitat (mangroves)
– Untreated water contaminates local environment • But, it CAN be treated
http://www.biology.duke.edu/bio217/2005/ncm3/pond_liner.gif
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Raceways• Divert water from a
waterway– Must be treated before
being released back to waterway
– Rainbow trout• Pro’s:
– no by-catch– does not deplete wild
stocks– Provides jobs
• Con’s:– Can be costly to build– Untreated water– Escapees (invasive species)
http://www.lib.noaa.gov/korea/korean_aquaculture/raceway.files/baqbk001.jpeg
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Recirculating Systems• Enclosed tanks
– Water is cleaned & reused– Striped bass, salmon,
sturgeon– Environmentally sound
• Pro’s– Can help rebuild wild
populations– Provides jobs– Conserves wild stocks
• Con’s– Requires a lot of energy
and thus $$
http://www.ag.auburn.edu/fish/image_gallery/data/media/77/Recirc_Kent_Seatech_jpg.jpg
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Shellfish Culture• Ropes, plastic trays,
mesh bags– Shellfish require only
clean water to survive
• Pro’s– Easy to do– Can clean up nutrient
rich water– Protects wild
populations
• Problems:– Waste accumulation– disease
http://www.whoi.edu/cms/images/oceanus/2005/6/v43n1-kitepowell3en_10837.jpg
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Why should we bother?FoodLong term
economicsOverfishing
correlates with:Low biodiversity in
the environmentHarmful algal
bloomsBeach closures
Darker color = more protein obtained from seafood
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Why should we bother?While some recover
after collapse, many do not (or at least, have not)CodAtlantic Bluefin tunaPacific Northwest
Salmon
There used to be wars over Atlantic cod, now they are almost gone….
http://www.codgen.olsvik.info/cDNA%20libraries.html
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Seafood Choices
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http://www.edf.org/page.cfm?tagID=16150
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Issue: Imported FishThe seafood Americans eat largely comes
from abroad
Problem: many nations that supply us with farmed fish do not adequately regulate these operations
Solution: policymakers and fish farmers worldwide need to implement strong standards for aquaculture operations
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Issue: Economic and ecological damageSome fish farming does economic and
ecological damage in the long runexample, in Thailand, Ecuador and many other
tropical nations, coastal forests of mangroves were cut down in the past and replaced with shrimp farms. Water degrades and farm closes: no farm OR mangrove
Problem: unregulated aquaculture can destroy ecological and human communities
Solution: responsible aquaculture
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Issue: Water PollutionProblem: Some production systems allow
uneaten food, fish waste and drugs and chemicals to pass into surrounding waters, where they can harm ecosystems and impair water quality
Solution: Use closed recirculating systems Grow more than one species (mussels raised on
ropes suspended in the ocean can help cleanse waters polluted by salmon raised in net pens.
Minimize use of antibiotics and anti-parasite drugs
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Issue: Depleting wild fish stocksProblem: Deplete food resources for wild cousins of
farmed fish Farming predatory fish like salmon can use huge
amounts of small, oily wild fish like anchovies, menhaden, mackerel and herring, leaving no food for wild fish
~1/3 of the current annual catch has been used for animal feed
Solution:Farm vegetarian or semi-vegetarian fish such as tilapia
and catfish or filter-feeders like mussels or clamsFeed predatory fish a semi-vegetarian diet supplemented
with fish byproducts
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Issue: Invasive SpeciesProblem: Escaped farmed fish can pose serious
threats to wild fish populations by competing with them for food and habitat and transmitting disease and parasites
Solution:Farm species native to the region to reduce the
potential harm from introducing a new fish species.Use closed systems like tanks, rather than "leaky"
net pens or cages, to prevent escapes.Mark fish and require public reporting of escapes, to
identify culpable suppliers.
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Issue: Endangering Sea AnimalsProblem: To keep them from feeding on
captive fish, wildlife such as seals, sea lions and birds are often harassed with firecrackers or loud underwater speakers that can cause disorientation, pain or hearing loss.
Solution:Site farms far from places where marine
mammals live or hunt, or birds congregate. Use tight nets to prevent access by predators
to ponds, tanks, and net cages.