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About Food & Water WatchFood & Water Watch is a nonprot consumer organization that works to ensure clean water and safe food. We chal-
lenge the corporate control and abuse of our food and water resources by empowering people to take action and by
transforming the public consciousness about what we eat and drink. Food & Water Watch works with grassroots or-
ganizations around the world to create an economically and environmentally viable future. Through research, public
and policymaker education, media and lobbying, we advocate policies that guarantee safe, wholesome food produced
in a humane and sustainable manner, and public, rather than private, control of water resources including oceans,
rivers and groundwater.
Main Ofce1616 P St. NW, Suite 300
Washington, DC 20036tel: (202) 683-2500fax: (202) [email protected]
www.foodandwaterwatch.org
Copyright September 2009 by Food & Water Watch. All rights reserved. This report can be viewed or downloaded atwww.foodandwaterwatch.org.
About the Alliance for Sustainable AquacultureAlliance for Sustainable Aquaculture (ASA) is a collaborative group of researchers, business owners, non-prot
organizations and interested members of the public working to further Recirculating Aquaculture Systems (RAS) in
the United States through research, education, legislative work and advocacy. We believe that RAS, closed-looped
and biosecure aquaculture operations, are the best option to meet our countrys need for a clean, green, sustainable,
healthy seafood source to supplement our wild sheries.
1616 P St. NW, Suite 300Washington, DC 20036tel: (202) 683-2500fax: (202) [email protected]
www.foodandwaterwatch.org/asa
On the Cover
California Ofce25 Stillman Street, Suite 200San Francisco, CA 94107tel: (415) 293-9900fax: (415) [email protected]
Images rom let to right
Methane fame generated rom waste captured by RAS.Photo courtesy o Dr. Yonathan Zohar at UMBI Center O Marine Biotechnology
Lettuce and other vegetables growing in RAS aquaponic tanks at UVI.Photo courtesy o Dr. James Rakocy at the University o the Virgin Islands in St. Croix.
Shrimp produced in a RAS acility at Blue Ridge Aquaculture.Photo courtesy o Mr. Martin Gardner rom Blue Ridge Aquaculture in Martinsville, VA.
Nile tilapia, a species oten produced in RAS.
RAS tanks or raising tilapia.
Photo courtesy o Dr. Martin Schreibman at Brooklyn College, CUNY, Aquatic ResearchEnvironmental ssessment Center (AREAC)
This report is a joint project of the Alliance for Sustainable Aquaculture and Food & Water Watch.
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Land-Based ReciRcuLating
aquacuLtuRe systems
a more sustainable approach to aquaculture
Table of Contentsiv Executive Summary
1 Introduction
1 What Is RAS?
2 Types of RAS: Freshwater and Saltwater
3 Why RAS Can Be an Important Fish Production Method for the United States
4 RAS Factors
8 Research and Development
10 Future Improvements
12 Specifc Commercial Case Studies
13 Conclusion
14 Endnotes
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Executive Summary
This report,Land-Based Recirculating Aquaculture Systems, provides an introduction to Recirculating Aquaculture
Systems (RAS). RAS are closed-loop sh farming facilities that retain and treat water within the systems. This form
of land-based aquaculture is quickly gaining popularity in the United States.Land-Based Recirculating Aquaculture
Systems addresses why RAS could be an important method of producing more sh for the United States; highlights
research, development and technical innovations in RAS; and discusses concerns and recommendations for thefuture of these systems.Land-Based Recirculating Aquaculture Systems also provides commercial case studies of
existing successful RAS operations in the United States.
Consumer demand for cleaner, greener, safer seafood is on the rise. Many popular sh, like tuna, cod and certain
snapper are depleted in the wild from many years of poor management, overshing and other ecological problems
like pollution and damage to key habitat areas. There is a need to supplement wild-caught sh to meet consumer
demand for seafood. One method to produce more sh is known broadly as aquaculturethe rearing of aquatic
animals in captivity. Aquaculture is also often called sh farming, as it can be likened to the farming of other food
animals, like chickens, pigs and cattle. Aquaculture is increasing worldwide; between 2004 and 2006 the annual
growth rate of this industry was 6.1 percent in volume and 11 percent in value.
Widespread open-water sh farming methods, such as coastal ponds and open-ocean aquaculture (OOA), can seri-ously damage marine ecosystems and are far from providing the safe and sustainable seafood many consumers want
In particular, OOAthe mass production of sh in huge oating net pens or cages in open ocean watersraises
concerns about consumer safety, pollution of the marine environment and conicts with other ocean uses.
Fortunately, RAS can likely provide a cleaner, greener, safer alternative to open-water farms that does not compete
with other ocean uses. These systems are usually land-based and reuse virtually all of the water initially put into the
system. As a result, RAS can reduce the discharge of waste and the need for antibiotics or chemicals used to combat
disease and sh and parasite escapesall serious concerns raised with open-water aquaculture.
RAS provide a diversity of production options. Tilapia, catsh, black seabass, salmon, shrimp, clams and oysters are
just a few examples of what can be raised in these systems. RAS can also be operated in tandem with aquaponics
the practice of growing plants using water rather than soil to produce a variety of herbs, fruits and vegetables suchas basil, okra, lettuce, tomatoes and melons. RAS range from small-scale urban aquaculture systems in individual
homes to larger, commercial-scale farms that can produce sh and produce equaling millions of dollars in sales each
year.
Currently, research and development is being conducted at academic, government and business facilities across the
country to continuously improve the techniques and methods used in RAS. With innovations in waste management
systems, sh feeds and energy usage, RAS has the potential to be a truly safe and sustainable aquaculture industry.
In recent years, the U.S. government has been shockingly insistent that development of open-water aquaculture,
in particular ocean aquaculture, is the best way to have an increased seafood supply in the United States. Given the
many ecological concerns associated with OOA, rather, the United States should be looking to explore more sus-
tainable sh production, such as RAS. This report challenges natural resource managers and consumers to be moreactive in helping to promote a cleaner, greener, safer domestic seafood supply by learning more about RAS and re-
questing grocery stores and restaurants carry RAS products rather than those from open-water aquaculture systems.
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What Is RAS?
Recirculating aquaculture systems (RAS) are closed-
loop facilities that retain and treat the water within the
system. The water in RAS ows from a sh tank through
a treatment process and is then returned to the tank,hence the term recirculating aquaculture systems.4 RAS
can be designed to be very environmentally sustainable,
using 90-99 percent less water than other aquaculture
systems.5 RAS can reduce the discharge of waste, the
need for antibiotics or chemicals used to combat disease,
and sh and parasite escapes. RAS have been under
development for the over 30 years, rening techniques
and methods to increase production, protability and
environmental sustainability.6
Various methods can be used to clean the water from the
sh tanks and make it reusable. Some RAS sh farms
incorporate aquaponics the practice of growing herbs
and vegetables in water into their system. Plants need13 elements to grow; the wastewater from the sh tanks
naturally provides 10 of these elements.7 The plants
thrive in the nutrient-rich system water, and they actu-
ally help to purify it for reuse the plants absorb the
nutrients and the cleaned water can go back to the sh
tanks!
Consumer demand for cleaner, greener, safer seafood is on the rise. Popular speciesof wild sh are depleted,1 leaving many people looking to aquaculture to help meetthe demand for seafood. Aquaculture production the rearing of aquatic plants andanimals in captivity is increasing worldwide; between 2004 and 2006 the annualgrowth rate was 6.1 percent in volume and 11 percent in value.2 There are many formsof aquaculture; recirculating aquaculture systems (RAS), coastal ponds and open-
water net pens are a few major types. Open-water aquaculture systems are, as theysound, open to air and water, and can therefore have a risk of air- or water-bornecontaminants.3 RAS are closed, controlled, bio-secure systems that retain and treat
water within the system, reducing the risk of contamination from air- and water-bornecontaminants.
Introduction
Lettuce and other vegetables growing in RAS aquaponic tanks at UVPhoto courtesy o Dr. James Rakocy at the University o the Virgin Islands in St. Croi
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Types of RAS: Freshwater andSaltwater
Recirculating aquaculture systems can be divided into
two main categories: freshwater and saltwater opera-
tions. Each of these can be paired with specic technolo-
gies designed to maximize efciency within the system,
minimize efuent discharge and occasionally to work in
a symbiotic relationship with other technologies, re-
viewed in brief below.
Freshwater RAS
Freshwater RAS can include the production of such
sh as tilapia, catsh, eel or striped bass, among oth-
ers. One innovative method explored in conjunction
with freshwater RAS is aquaponics, as described above.
Aquaponics works by allowing for the growth of plants,
sh and nitrifying bacteria simultaneously each of
which feed off of the waste of the others to create a sys-
tem that requires very little maintenance, aside from pH
monitoring, to ensure optimal growth.8 A major concern
of most aquaculture systems is the buildup of ammonia
(NH3) and its derivatives from sh waste, which can be
fatal to sh even at very small concentrations as little
as .08 mg/L. Aquaponic systems work by introducing
nitrifying bacteria, which feed on the ammonia in sh
waste to convert it into nitrate, which is non-toxic to the
sh and benecial for the plants.9 Another innovation in
freshwater RAS involves the use of microalgae to reduce
the prevalence of carbon dioxide within these systems
and provide a food source to developing sh.
Saltwater RAS
Saltwater RAS can take several forms as well, and are
sometimes referred to as marine RAS. One type of sys-
tem that has been researched extensively in recent yearsis the high-rate algal pond, or HRAP. HRAPs make
use of macroalgae seaweed in order to reduce the
amount of waste in RAS. In fully recirculating systems,
nitrate and phosphate levels accumulate at a rate that is
proportional to sh density; thus, the larger the produc-
tion scale, the more efuents will appear in the system
and need treatment in order to ensure the continued
growth of the sh.10 Macroalgae can accomplish this be-
cause they absorb the nutrients that are in sh waste for
their own growth, the same way that aquaponics produce
plant growth from these nutrients. The difference in ma-
rine RAS is that the seaweed is generally not intended for
consumption, and the seaweed will thrive in high-salin-
ity environments, whereas land-based plants would not.
Macroalgae HRAPs have been found to be even more
productive in the removal of wastes than the microalgae
that are used in freshwater systems, so this is considered
a very viable route for marine RAS.11 One factor that is
holding back more extensive use of the HRAP system is
that seasonality can affect the productivity of micro- and
An example o a small-scale RASPhoto by Eileen Flyn
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macroalgae alike with higher productivity rates in the
warmer, brighter summer months.
Why RAS Could Be an Important FishProduction Method for the United
States
How RAS Function
A key feature of RAS is that it re-uses water; the water is
recirculated continuously throughout the system. All of
the tanks and various components in RAS are connected
by pipes. Water ows from the sh tank to the mechani-
cal lter where solid waste is removed. The water then
ows into a biological lter that converts ammonia to
nitrate. Some RAS incorporate plant tanks as a biologi-
cal lter plants absorb nutrients, thus cleaning the
water. Other systems use special tanks that are designedto promote good bacteria growth the bacteria act as
a lter. After being treated in the mechanical and
bioltration components, the water ows back to the sh
tank.
Biosecurity
RAS sh farms are often fully closed and entirely con-
trolled, making them mostly biosecure diseases and
parasites cannot often get in. Biosecurity means RAS
can frequently operate without any chemicals, drugs or
antibiotics, making a more natural product for consum-ers. Water supply is a regular route of pathogen entry,
so RAS water is often rst disinfected or the water is
obtained from a source that does not contain sh or in-
vertebrates that could be pathogen carriers (rain, spring
or well water are common sources).12 Biosecurity in RAS
requires that the systems be designed for easy clean-
ing, completely and frequently, to reduce pathogens.13
Being self-contained and cleaner also means RAS can be
located near markets or within land-locked communi-
ties that will use the sh, rather than by natural water
sources like oceans or rivers RAS does not need to be
located on water to supply the system or for drainage.Locating RAS by the markets or communities they serve
means they can have a smaller carbon footprint due to
reduced shipping distance and provide a fresher product
to the consumer.
Water Reuse
RAS are completely contained systems that reuse most
of the water from the sh holding tanks. Wastes are
removed; water is treated and then recycled back to the
tanks. Ideally, RAS only replace very small percentages
of the total water volume, due to some loss during waste
removal and/or evaporation (less than 1 percent daily
water exchange).14 This low replacement volume is espe-
cially important in saltwater systems since salt water can
be more expensive and more difcult to make or obtain
than fresh water.
Space and Production Efciency
RAS production levels are often higher than those in oth-
er forms of aquaculture. RAS control the environmental
conditions in which products are raised, thus allowing
for optimal year-round growth.16 Some RAS can produce
market-sized sh in just nine months, compared to the
15 to 18 months it often takes for the sh raised in other
Open-Water Aquaculture
Open-water aquaculture, (when in the ocean, also known
as oshore aquaculture, ocean sh arming, open-ocean
aquaculture and other, similar terms), is the mass production o
sh in coastal ponds, or large foating pens or cages in ocean
waters. Just one arm is a large-scale operation.
While open-water sh arming is a airly common practiceworldwide (we dont do it large-scale in U.S. waters currently) it
can pose real threats to human health and the environment:
Fragile habitat can be permanently damaged rom clearing
out space to site the arm or rom anchors to hold down
cages.
Fish in cages can spread diseases to wild sh, or escape
and intermix with wild sh, interering with or even
overtaking natural populations.
Open-water sh arms allow ree fow o water between
the sh enclosures and the ocean. Concentrated amounts
o sh ood, wastes, diseases and any chemicals orantibiotics that may be used in arms can fow straight into
open waters, polluting habitat and wildlie and impeding
recreational water uses like swimming and diving.
Chemicals used in production may remain in the sh and be
transerred to people who consume them later.
Because there are so many potential problems with open-water
arms, the United States should explore other options, like RAS.
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systems to grow to market size.17 It takes 197.6 acres of
open ponds to produce the same amount of shrimp that
a RAS farm can raise on just 6.1 acres.18 Tilapia, cobia,
black sea bass, branzini, salmon, trout and shrimp are
among the many seafood products being raised in RAS.
Aquaponic RAS produce a large array of herbs, vegeta-
bles, fruits, owering plants and seaweeds as well.
RAS Factors
Water Quality and Waste Management
The critical water quality parameters in RAS are dis-
solved oxygen, temperature, pH, alkalinity, suspended
solids, ammonia, nitrite and carbon dioxide (CO2).19
These parameters are interrelated in a complex series of
physical, biological and chemical reactions.20 Monitoring
and making adjustments in the system to keep the levels
of these parameters within acceptable ranges is very
important to maintain the viability of the total system.
The components that address these parameters can vary
from system to system.
Dissolved Oxygen
Oxygen that is dissolved in the water is called dissolved
oxygen or DO. Fish take in DO from the water through
their gills. The amount of DO that a sh needs to stay
alive and grow depends on the species and size of sh,
as well as the effects of the other water quality param-
eters.21 A sh with a higher metabolic rate will consume
DO at a higher rate. 22 Oxygen is also critical to the meta-
bolic processes of the bacteria living in the system that
break down ammonia and solid waste.23
Low levels of DO in the system can reduce productivity
of the sh and bacteria, ultimately resulting in mortali-
ties. DO levels are monitored as water is leaving the
sh tank or the biological lter (where a large amount of
bacteria lives) to accurately access the level of DO that is
available to sh and bacteria respectively.24
DO can be maintained in RAS through aeration, either
with atmospheric oxygen (air) or pure oxygen. Standard
sources of air in aquaculture are blowers, air pumps or
compressors. The primary differences between theseoptions are the water and DO pressure requirements
and volume discharged.25 Airstones, pieces of limewood
or porous rock, are often used to release the air into the
water.26 Pure oxygen sources are used when diffusing
atmospheric oxygen (air) into the system cannot keep
up with the consumption of DO by the sh and bacte-
ria. Three sources of pure oxygen often used for RAS
are high-pressure oxygen gas, liquid oxygen and on-site
Oxygen dissolving into a RASPhoto by Eileen Flyn
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generators.27 U-tube aerators, packed columns, low
head oxygenators and down-ow bubble contactors are
component options for diffusing pure oxygen into the
system water. These components are all designed to use
a counter-ow of water and oxygen to enhance the gas-
liquid interface forcing more oxygen to dissolve into the
water.28 In general, warm-water sh grow best when DOconcentrations are above 5 mg/L.29
Temperature
Fish are cold-blooded; the temperature of the water in
which they live controls their body temperature. Water
temperature directly affects the physiological processes
of sh such as respiration rate, efciency of feeding and
assimilation, growth, behavior and reproduction.30 Fish
are often grouped into three categories based on pre-
ferred temperature ranges: cold-water species below 60
degrees Fahrenheit, cool-water species between 60 F to68 F and warm-water species above 68 F.31 To ensure
maximum growth and minimize stress, temperatures
need to be maintained in the species optimal range.
Indoor RAS allows the farm to have greater control over
the temperature of the ambient air that can impact the
water temperature. Heaters and chillers can be added to
RAS to maintain temperature, though this is not ideal in
terms of energy efciency.
At Skidaway Institute of Oceanography, Dr. Richard Lee,
an emeritus professor of oceanography, uses geothermal
chilling and solar heating to regulate the temperature ofhis RAS. The geothermal chilling is conducted through
a closed-loop pipe running down into the groundwa-
ter and back up to the surface (no water is exchanged
between the facility and the groundwater). The ground-
water is approximately 64.5 F and the contact of the cool
water on the outside of the pipe transfers the heat so that
the tank can maintain its temperature between approxi-
mately 79 F and 82.5 F during a Georgia summer.32 The
solar heating is conducted by running pipes carrying
system water through sheets of black plastic that trans-
fer the heat they absorb from the sun to the water in the
pipes. Using this method the RAS system had tempera-
tures between approximately 70 F and 77 F in the winter
when air temperature was not above 60 F in the same
time period.33
pH and Alkalinity
Monitoring of the pH level is among the most im-
portant tasks in RAS. The pH is directly affected by
concentrations of ammonia from sh wastes. When sh
waste is produced, most of it eventually breaks down
into nitrate, and nitrate accumulation tends to produce a
drop in pH and alkalinity, which can be harmful to sh if
it is not monitored properly.
34
The scale of pH ranges from 0 to 14, with lower numbers
demonstrating increased acidity and higher numbers
showing greater basicity. Seven is considered the equi-
librium point of freshwater, where it is neither acidic nor
basic. In freshwater RAS, pH is generally maintained
around 6 to 7.5. In aquaponic systems, pH may be main-
tained at a slightly lower level (around 5.5 to 6.5), where
the slightly higher acidity level helps plants to obtain nu-
trients. Some studies have been done in aquaponics sys-
tems to reconcile the lower optimal pH of plants with the
higher optimal pH of sh, and it has been found that apH as high as 7 can be maintained without reducing the
productivity of plants.35 Marine RAS needs to maintain
a slightly higher pH, as the average pH of ocean saltwa-
ter is around 8, which makes it somewhat basic. People
who work with recirculating systems need to monitor
pH carefully in order to keep levels within an accept-
able range for health and growth of the sh. Some of
the aforementioned technologies, such as high rate algal
ponds, can act as a counterbalance to the accumulation
pH testersPhoto by Eileen Flyn
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of certain chemicals within an RAS and can help to bal-
ance pH levels naturally.
Alkalinity is a measure of the pH-buffering capacity
of water.36 The principle ions that contribute to alka-
linity are carbonate (CO3-) and bicarbonate (HCO
3-).
Supplements may be added to water to adjust the alka-linity. Alkalinity of fresh water ranges from less than
5mg/L to more than 500mg/L and salt water is about
120mg/L CaCO3.37
Waste Removal: Ammonia, Nitrite,Nitrate, Solid and Suspended Waste(Without Aquaponics)
One major benet of RAS over other forms of aquacul-
ture is the ability to capture, treat and/or utilize waste
from the system. In general, solid wastes, including
feces and uneaten feed, are ltered and removed from
the system. Once removed, these solids can be treated
or utilized in a secondary function (converted to energy,
fertilizer and possibly even feed). Systems that do not
effectively and quickly remove sh fecal matter, uneaten
food and other solids from the water will never produce
sh economically.38
Nitrogen is required in small amounts by sh for good
health and growth. Nitrogen that is not utilized by sh
becomes nitrogenous waste in the system and needs to
be removed. There are several sources of nitrogenouswaste including: feces, urine, excretions from gill dif-
fusion, uneaten food and dead and dying sh.39 The
decomposition of these nitrogenous compounds is par-
ticularly important because of the toxicity of ammonia,
nitrite and to some extent nitrate to sh.40 Ammonia
exists in two forms: non-ionized NH3
and ionized NH4+.
Non-ionized ammonia is the most toxic form, due to its
ability to move across cell membranes.41 An increase
in pH, temperature or salinity increases the propor-
tion of the non-ionized form of ammonia.42 Nitrite is
the intermediate product in the process of nitrication
of ammonia to nitrate and is toxic because it affects thebloods ability to carry oxygen.43 In RAS, efuent water
is passed through a biolter containing bacteria that
converts ammonia to nitrite and nally to nitrate.44 This
conversion from ammonia and nitrite to nitrate is called
nitrication; the bacteria in this process require ample
amounts of oxygen.45 Plants in an aquaponic system will
act as the biolter converting ammonia and nitrates. In
RAS facilities without plants in the system (aquaponics),
the bioltration component consists of media with living
benecial bacteria that converts harmful ammonia and
nitrite to nitrate. Algae and bacteria oating in the water
column can also convert ammonia to nitrate.46 Nitrateis the end product of nitrication and is the least toxic; it
can be removed from the system by daily water changes
or denitrication.47 Denitrication is the process of
converting nitrate to nitrogen gas; the bacteria in this
process do not require oxygen.48Treatment processes or recycling water at the USDA ARS National Cold Water
Marine Aquaculture Center, Franklin, ME.Photo courtesy o Dr. Steve Summerelt o the Freshwater Institute, Shepherdstown, WV.
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Carbon dioxide
Dissolved carbon dioxide is another product that can
accumulate in high-density RAS. Large-scale RASsystems must supplement their tanks with pure oxygen
for a greater quantity of sh to be bred, but this results
in insufcient natural removal of the carbon dioxide
(CO2) that is then produced.49 (In lower-density systems,
oxygenation is generally unnecessary, as sufcient water
exchange and aeration occurs to naturally balance levels
of both oxygen and CO2.)
Excessive levels of CO2
can result in changes in pH
towards acidication, which can be detrimental to sh
if the pH level drops too low. Various technologies have
been tested to reduce the amount of carbon dioxide inthe water of these high-density systems. One method of
addressing excessive carbon dioxide is the use of chemi-
cals, which can balance pH levels and thereby eliminate
the CO2
in RAS.50 Sodium hydroxide and sodium bicar-
bonate are two chemicals commonly used in aquaculture
for this purpose. Both function by increasing alkalinity
in the water, resulting in a series of chemical reactions
which break down carbon dioxide and reformulate it into
lesser molecules.
Another process for carbon dioxide elimination is calledaeration stripping, a process in which water is forced
through a series of cascading stripping columns that
expose the water to air and result in the release of dis-
solved CO2
into the atmosphere. Experiments have been
done to determine the optimal ratio of air to water as it
cascades through the stripping columns, and for now,
experiments suggest that higher ratios of air to water
implying a slower ltration process improve the
efciency of carbon dioxide stripping from a recirculat-
ing system.51
Similar to aeration stripping, a third type of carbon
dioxide removal is performed by vacuum degassing, a
process that vents excessive gasses through a vacuum or
pump system. The process of carbon dioxide elimination
is similar to the manner in which it is eliminated in the
aeration stripping process.52
Basil grown in a RAS aquaponics tank at UVI.Photo by Eileen Flynn
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The overall waste-capture efciency of a full RAS facility
can be 100 percent.53
Researchers and industry experts are developing a vari-
ety of resourceful ways to deal with the waste produced
by RAS sh farms, such as creating fertilizer for crops
and plants. Some RAS farms turn the waste into pelletsto create a feed ingredient for other sh or shrimp. Still
other RAS turn the waste into methane gas, which can be
used to help power generators. 54
Research and Development
Currently, research and development is being conducted
at academic, government and business facilities across
the country to continuously improve the techniques and
methods used in RAS to offer consumers cleaner, green-
er and safer products.
Urban Aquaculture as a Community-Based Option
Dr. Martin Schreibman, founder and director of the
Aquatic Research and Environmental Assessment Center
at the City University of New Yorks Brooklyn College,
is conducting research on RAS he calls urban aquacul-
ture. Dr. Schreibman is working with RAS of various
sizes that can be run virtually anywhere, in warehouses,
on browneld sites or right in your own home, utilizing
the hydroponic component of aquaponics to clean the
water. One aspect of his research involves aeropon-
ics, in which plants are suspended above the tanksand sprayed with system water every 10 to 15 minutes
instead of being submerged in the water.55 This process
reduces the horizontal space needed to run the system
when compared to other aquaponic systems. Urban
aquaculture can be located in or near populated areas,
so it can provide positive socio-economic benets like
jobs as well as fresh, safe seafood and produce to local
markets.56
Larger-Scale Aquaponics
Dr. James Rakocy, director of the University of theVirgin Islands Agricultural Experimental Station, con-
ducts RAS aquaponic research in a large-scale system
with plants growing on oating rafts. Foam rafts oat on
the surface of large water-lled hydroponic tanks. Plants
develop and expand atop the rafts, basked in sunlight,
while roots get maximum exposure to water by growing
This is an urban aquaculture/aquaponics system (it grows both fsh and plants) in a small setting in act it is in a part o a classroom at Brooklyn CollegePhoto courtesy o Dr. Martin Schreibman at Brooklyn College, CUNY, Aquatic Research Environmental Assessment Center (AREA
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beneath. Raft tanks have no size limitations. A disad-
vantage of raft culture exposing the roots to zooplank-
ton and snails that may grow in the tanks is addressed
through the addition of ornamental sh (tetras) and
red ear sunsh to consume these pests.57 Additional
research has been done rening waste management
components and water quality needs for optimal plantand sh growth. Dr. Rakocys research shows the tech-
nology UVI uses can be applied for an individual family
subsistence or commercial scale, while conserving water
and recycling nutrients. Researchers at the UVI facility
grow tilapia and continue to experiment with basil, okra,
lettuce, watermelon, mint, chives, tomatoes, cantaloupe,
cucumber, owers, squash, bok choy, collard greens and
sorrel (a locally grown plant used in a popular drink) and
other crops. The UVI commercial-scale aquaponic sys-
tem can annually produce up to 35,570 pounds of tilapia
and vegetables on 1/8 an acre of land.58
Various Species Grown in RAS
The list of aquatic species being researched and grown
in RAS is constantly broadening to include: oysters,
blue crabs, sea bream, branzini, cobia, red drum, black
seabass, bivalves, soft corals, horseshoe crabs, assorted
atsh, lobster, nautilus, tilapia, rainbow trout, striped
bass, salmon and assorted shrimp.
The list of plants that are grown in conjunction with
these aquatic species is also growing rapidly, including:
algae, seaweeds, basil, okra, lettuce, watermelon, mint,chives, tomatoes, cantaloupe, cucumber, owers, squash,
bok choy, collard greens, sorrel, arugula, peas and vari-
ous pharmaceutical plants
Fish Feed
Existing RAS farms and researchers are working to feed
their sh a more environmentally sustainable diet while
remaining nutritionally appropriate. One of the biggest
and most crucial hurdles faced by aquaculture has been
to decrease the amount of wild sh used as an ingredient
in sh feed. Traditionally, large amounts of wild sh areused to produce the pellet feed for farmed sh. Taking
prey sh from the oceans to feed farmed sh can deplete
ocean food chains and disrupt ecological balance. Work
is being done at various RAS farms to improve feed,
including reducing the amount of sh needed to be put
into feed; nding alternative feed ingredients (includ-
ing worms and algae);59 and even using waste to create a
healthy feed source.
Dr Richard Lee at Skidaway Institute of Oceanography
has found a unique solution to raising carnivorous sh
without taking wild sh. At the Skidaway RAS facility Dr
Lee grows black seabass to a market size of two poundsin one year by feeding them whole tank-raised tilapia.
The feed conversion rate is ve pounds of tilapia to one
pound of black seabass. The seabass grow twice as fast
when they are fed tilapia, when compared to being fed
the traditional shmeal pellet. Feeding a tank-raised
freshwater sh to a saltwater RAS raised sh also reduc-
es the chance of pathogen introduction.
A majority of commercial feeds use soybean as a com-
mon protein replacement for shmeal and sh oil. There
are some concerns with using soybean, a terrestrial
protein, in sh feed. In 2009, 91 percent of soybeansgrown in the United States were genetically modied.60
Another concern is that soybeans are high in estrogen
and do not occur naturally in the aquatic environment.61
In addition, soy protein is quite expensive. Many re-
searchers are looking to replace soybeans in feed with
other proteins that occur naturally in the aquatic en-
vironment, like algae, that could increase the nancial
sustainability of RAS.
Fish eed pelletsPhoto by Eileen Flyn
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Future Improvements
RAS is not yet perfect, but the benets of a controlled,
closed system with waste management should not be
overlooked. Additional research is being done to devel-
op new techniques and methods to continually improve
RAS.
Chemical Usage
Water supply is a common means of pathogen entry.
Water for RAS is often disinfected, or obtained from a
source that does not contain sh or invertebrates that
could be pathogen carriers (rain, spring or well water are
common sources).62 Biosecurity in RAS requires that the
systems be designed to be cleaned easily, completely and
frequently to reduce pathogens.63
When diseases do appear, a veterinarian and diagnos-
tic laboratory should be involved in determining the
specic disease and treatment, using chemicals that are
approved for use in food sh production.64 Many RAS
can operate without any chemicals, drugs or antibiotics,
making a more natural product for consumers.65
Energy Usage
RAS facilities require varying amounts of energy to run
the machinery that moves the water through the system
and treatment processes. Some producers using aqua-
ponics and facilities raising shrimp may be able to usefewer pieces of machinery to run the systems therefore
having reduced energy demands. Research is being
done by Dr. Timothy Pfeiffer at the U.S. Department
of Agricultures Agricultural Research Service to de-
termine the specic energy requirements for different
aspects of the treatment processes and how to get the
most efcient water treatment with the least amount of
energy.66 Dr. Yonathan Zohar, Director at University
of Maryland Biotechnology Institutes Center of Marine
Biotechnology (COMB), is using waste captured from
RAS to produce energy in the form of methane that
can be fed straight into a generator.67 Dr. Zohar andresearchers at COMB are also working to convert algae
biomass, produced in RAS, into bio-fuel.
Both freshwater and marine RAS have been the sub-
ject of experiments to enhance energy efciency.
Implementing solar heating for the maintenance of
proper temperature within the sh basin has been found
to reduce conventional energy requirements by 66 per-
cent to 87 percent, depending on the regional climate
where the RAS are located.68 Wind energy has also been
tested as a means to power reverse-osmosis membrane
ltration, which separates puried water from a concen-
trated brine of sh efuent, with some success.69 Many
of these technologies have been proven viable at a small-
scale, and implementation on large-scale (high-density)
RAS are ongoing.
Feed Efciency
In the production of farm-raised sh, the feed plays a
large role in determining sustainability and quality of
farmed sh. Farmed sh are often fed wild forage sh,
such as anchovies, sardines and herring, after being
processed into shmeal or oil. These prey sh are a
crucial part of the marine ecosystem, serving as food for
marine mammals, birds and large predatory sh. Since
Lettuce and other vegetables growing in RAS aquaponic tanks at UVPhoto courtesy o Dr. James Rakocy at the University o the Virgin Islands in St. Croi
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taking these sh from the oceans can disrupt food chains
and ecosystem balance, feed conversion rate is always
a concern with farm-raised sh. The ideal feed conver-
sion is one pound or less of wild sh to raise one pound
of farmed sh. Although existing feed sources do not
always have completely efcient 1:1 conversion rates,
RAS farms and scientists are conducting research anddeveloping techniques that can improve feed quality and
reduce the need for wild sh. Examples of innovations
in RAS feed efciency include nding alternative feed
ingredients, such as worms and algae, improving feed
quality by using algae to increase protein content and
raising prey sh in RAS, instead of harvesting wild for-
age sh, to feed larger predatory sh.70
Organic?
Organic foods are produced under conditions in which
all inputs are controlled. RAS is the only method ofraising sh that can completely control the production
environment. Being a closed-loop system, RAS can
better ensure sh and plants are not being exposed to
synthetic fertilizers or pesticides, growth hormones,
sewage sludge, antibiotics or any other articial feed or
treatments. Other forms of aquaculture that allow water
to ow freely in and out of the holding ponds or cages
can not control what chemicals and pollutants are being
carried with the water. Some RAS/aquaponic facilities
have been certied organic for the plants produced.
Not a Natural Environment, but Still aHealthy One
To achieve economic viability, RAS farms run their sys-
tems with a higher density of sh per tank than would be
found in the wild. Density depends primarily on water
quality, sh species and size.71 Overcrowding of younger
sh is avoided to allow them optimal room to grow dur-
ing their rapid growth stage.72 As sh grow they may
be moved to reduce densities to maintain good water
quality and to optimize sh health and growth until they
reach market size. RAS sh farmers avoid keeping sh
at densities that can be detrimental to sh health; for ex-ample, trout raised at high densities can develop eroded
ns.73 Researchers regularly experiment with densities to
ensure optimum health and productivity.
Algae growing in tubes in RAS at COMB acilityPhoto courtesy o Dr. Yonathan Zohar at UMBI Center O Marine Biotechnolog
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Specifc Commercial Case Studies
Premier Organic Farms
Premier Organic Farms combines organic growing prac-
tices in controlled ecological environments as the basis
for their state-of-the-art, eco-friendly aquaponics farm-
ing operation, which can run anywhere in the world.74
The company has done extensive research and develop-
ment over the past three years on its design known as
the Pod Growing Unit.75 Premier raises tilapia in RAS
facilities that are linked to plant tanks producing but-
ter and Boston lettuce, herbs, peppers and tomatoes as
its core products.76 Premier Tilapia is fed an all-natural,
nutritionally balanced diet of organic grain and pro-
tein.77 Premier Organic Farms does not use antibiotics
or chemicals.78 Nor does it use hormones.79 Other farms
use certain hormones to convert female sh to males (to
avoid unintentional breeding in grow out tanks beforethe sex of each sh can be identied).80 Premier plans
to build commercial Pod Growing Units near strategic
markets across the United States over the next ve years,
with further expansion worldwide as demand dictates.
One Pod is predicted to produce $43 million in rev-
enue annually from all segments (tilapia and mixed
organic produce).81
Premiers growing system uses 80 percent less water
than conventional agriculture.82 The companys goals
are to produce high quality, safe food while achieving a
carbon neutral footprint.
Marvesta Shrimp Farms
Marvesta Shrimp Farms, located in Hurlock, Maryland,
is growing saltwater shrimp miles away from the coast.
Water from the Atlantic is brought in and ltered down
to below 50 microns and run through an ultraviolet lter
(which removes unwanted bacteria, algae and viruses).83
Co-founder Scott Fritze says that the water is 100 per-
cent recirculating and completely bio-secure, with no
efuent and little waste. The nitrication system that
they have in place now is entirely indoors and producessome feed for the shrimp within the tanks. The small
amount of waste produced by the system is composed of
undigested protein, and can be easily dried out and dis-
posed of.84 Marvesta does not use antibiotics, hormones,
pesticides or chemicals of any kind.
Blue Ridge Aquaculture
Blue Ridge Aquaculture, established in 1993, pro-
duces RAS tilapia at their headquarters in Martinsville,
Virginia. The 80,000 square foot facility produces four
million pounds of tilapia a year. 85 An estimated 75,000
pounds of live tilapia are shipped to market each week
from the facility, making Blue Ridge the worlds largest
indoor producer of tilapia.86 Blue Ridge Aquaculture as-
serts that its products are free of growth hormones, pes-
ticides, antibiotics, and synthetic chemicals.87 According
to the companys president, Bill Martin, Blue Ridge
Aquaculture is one of few tilapia farms that hand select
broodstock for desirable characteristics, rather than us-
ing hormones.88
Blue Ridge is partnering with feed production com-
pany Marical and Virginia Tech to research low-salinity
technology and feed options for cobia in RAS.89
Thecompany hopes to research other marine species once
they have brought the cobia production up to commer-
cial levels.90 Blue Ridge is also partnering with Virginia
Tech on a 30,000-square-foot RAS facility dedicated to
shrimp production.91 The aim is to bring shrimp produc-
tion up to 325 million pounds per year.92 In 2007, Blue
Ridge began a joint venture with aquaculture company
West Virginia Aqua, to produce over 300,000 pounds of
Atlantic salmon and rainbow trout in RAS.93
Computer rendering o the 4,800 L/min water recirculating system at th
Conservation Fund Freshwater InstituteSummerelt, S.T., Sharrer, M.J., Hollis, J., Gleason, L.E., Summere
S. R. 2004. Dissolved ozone destruction using ultraviolet irradiation
a recirculating salmonid culture system. Aquacultural Engineering 3
209-224. Drawing courtesy o Marine Biotech Inc. (Beverly, MA
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Conclusion
Consumers love seafood, and with wild sh stocks de-
pleted, aquaculture is likely to be supplying increasing
amounts of sh for food. However, not all sh farming
methods are equal. In order to ensure safer and more
sustainable seafood, consumers are more regularly ask-
ing about how their sh was produced before making
seafood choices. Common forms of aquaculture, such
as open-water systems, can pollute the marine environ-ment with chemicals and waste, and may produce sea-
food contaminated with pesticides and antibiotics. These
are not acceptable factors for most consumers seeking
greener, more healthful options.
RAS, on the other hand, are closed, controlled, bio-
secure systems. Since RAS retain and treat water within
the system, they reduce waste discharges and the need
for chemicals and antibiotics. RAS can be efcient in
production and space usage and can range from small-
scale to commercial operations growing a variety of
different sh and plants.
RAS are currently operating in the United States. In
fact, RAS have been under development for over 30
years, rening techniques and methods to increase pro-
duction, protability and environmental sustainability. 94
Academic, government and business facilities across the
country are conducting research and further improving
and expanding RAS. Premier Organic Farms, Marvesta
Shrimp Farms and Blue Ridge Aquaculture, highlighted
in this report, are just a few examples of successful com-
panies that are producing RAS seafood.
Technical innovations are essential for the continued
growth of the aquaculture sector. Instead of pushing
OOA, which can damage the marine environment and
may pose a threat to consumer health, the U.S. govern-
ment needs to play a vital role in promoting opportuni-
ties to develop cleaner, greener, safer aquaculture in the
United States,such as RAS. 95
Recommendations
Federal and State governments should increase funding
to RAS researchers to help provide consumers with a
cleaner, greener, safer seafood aquaculture option.
If standards must be set for an organic label for sh, RAS
raised sh should viewed as the only true option, due to
the controlled, closed-loop nature of RAS.
Consumers should ask grocery stores and restaurant
managers whether the seafood they sell comes from
domestic RAS farms. If not, they should request U.S.
RAS-produced seafood as an alternative to imported,
open-water farmed sh.
Fish waste being distributed by a manure spreadeSummerelt, S.T. and B.J. Vinci. (2008). Better management practices or recirculating systems. Pages 389-426 in C.S. Tucke
and J.A. Hargreaves (editors), Environmental Best Management Practices or Aquaculture. Blackwell Publishing: Ames, Iow
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Endnotes
1 Fishwatch.gov
2 FAO Fisheries and Aquaculture Department, Food andAgriculture Organization of the United Nations. The State ofWorld Fisheries and Aquaculture 2008 Rome, Italy. 2009 at 16.
3 Timmons, M.B. and J.M. Ebeling. (2007) Recirculating
Aquaculture. Cayuga Aqua Ventures at 3.4 Timmons at 30.
5 Timmons at 6.
6 Timmons at 1.
7 Rakocy, James. The UVI Aquaponic System. Clean, Green,Sustainable Recirculating Aquaculture Summit. WashingtonD.C.: hosted by Food and Water Watch. January 2009.
8 Tyson, R.V. et al, Effect of Water pH on Yield and NutritionalStatus of Greenhouse Cucumber Grown in RecirculatingHydroponics. Journal of Plant Nutrition 31.11 (2008): 2019
9 Ibid.
10 Metaxa, E., et al, High rate algal pond treatment for water reusein a marine sh recirculation system: Water purication and shhealth. Aquaculture 252 (2005).
11 Pagand, P. et al, The use of high rate algal ponds for the treat-
ment of marine efuent from a recirculating sh rearing system.Aquaculture Research 31 (2000).
12 Timmons at 621
13 Timmons at 620.
14 Torsten, E.I. Wik, et al. Integrated dynamic aquaculture andwastewater treatment modeling for recirculating aquaculturesystems. Aquaculture. 287. 2009 at 361-370.
16 Timmons at 7.
17 Zohar, Yonathan. Environmentally compatible, recirculatedmarine aquaculture: addressing the critical issues. Clean, Green,Sustainable Recirculating Aquaculture Summit. WashingtonD.C.: hosted by Food and Water Watch. January 2009.
18 Conversion of information from hectares to acres by Food &Water Watch from: Moss, Shawn. An integrated approachto sustainable shrimp aquaculture in the U.S. Clean, Green,
Sustainable Recirculating Aquaculture Summit. WashingtonD.C.: hosted by Food and Water Watch. January 2009. Samocha,Tzachi. Overview of some sustainable, super-intensive micro-bial biooc-rich shrimp production systems used by Gulf CoastResearch Lab, Waddell Mariculture Center and AgriLife ResearchMariculture Lab. Clean, Green, Sustainable RecirculatingAquaculture Summit. Washington D.C.: hosted by Food andWater Watch. January 2009.
19 Timmons at 39.
20 Timmons at 47.
21 Timmons at 88.
22 Timmons at 88.
23 Timmons at 90.
24 Timmons at 89.
25 Timmons at 412.
26 Timmons at 413.27 Timmons at 413.
28 Timmons at 413-426.
29 Timmons at 50.
30 Timmons at 51.
31 Timmons at 51.
32 Lee, Richard. Rapid growth of black sea bass Centropristis stria-ta in recirculating systems with geothermal cooling, solar heating,tilapia diet and microbial mat/seaweed lter. Clean, Green,Sustainable Recirculating Aquaculture Summit. WashingtonD.C.: hosted by Food and Water Watch. January 2009.
33 Lee, Richard. Rapid growth of black sea bass Centropristis stria-ta in recirculating systems with geothermal cooling, solar heatingtilapia diet and microbial mat/seaweed lter. Clean, Green,Sustainable Recirculating Aquaculture Summit. WashingtonD.C.: hosted by Food and Water Watch. January 2009.
34 Neori, Amir, et al, Biogeochemical processes in intensivezero-efuent marine shculture with recirculating aerobic andanaerobic biolters. Journal of Experimental Marine Biologyand Ecology 349 (2007): 241.
35 Tyson, et al, Effect of Water pH on Yield, 2019.
36 Timmons at 56.
37 Timmons at 57.
38 Timmons at 115.
39 Timmons at 53.
40 Timmons at 275.
41 Timmons at 54.
42 Timmons at 54.
43 Timmons at 55.
44 Timmons at 275.
45 Timmons at 277.
46 Timmons at 281-283.47 Timmons at 56.
48 Timmons at 275.
49 Summerfelt, Steven T., et al., Evaluation of full-scale carbondioxide stripping columns in a coldwater recirculating system.Aquacultural Engineering 28 (2003).
50 Summerfelt, Steven T., et al, Oxygenation and carbon dioxidecontrol in water reuse systems. Aquacultural Engineering 22(2000).
51 Summerfelt, et al, Evaluation of full-scale carbon dioxide strip-ping columns, 2003.
52 Summerfelt, et al, Oxygenation and carbon dioxide control,2000.
53 Timmons at 10.
54 Zohar, Yonathan. Environmentally compatible, recirculatedmarine aquaculture: addressing the critical issues. Clean, Green,Sustainable Recirculating Aquaculture Summit. WashingtonD.C.: hosted by Food and Water Watch. January 2009.
55 Schreibman, Martin. Urban Aquaculture: The promises andconstraints. Clean, Green, Sustainable Recirculating AquacultureSummit. Washington D.C.: hosted by Food and Water Watch.January 2009.
56 Schreibman, Martin. Urban Aquaculture: The promises andconstraints. Clean, Green, Sustainable Recirculating AquacultureSummit. Washington D.C.: hosted by Food and Water Watch.January 2009.
57 Rakocy, James. The UVI Aquaponic System. Clean, Green,Sustainable Recirculating Aquaculture Summit. WashingtonD.C.: hosted by Food and Water Watch. January 2009.
58 Food & Water Watch staff email exchange with Dr. James
Rakocy, University of the Virgin Islands. June 22 September 7,2009.
59 Steve Craig and other from the Summit
60 Kidd, Karen. Effects of Synthetic Estrogen on AquaticPopulation: A Whole Ecosystem Study, Freshwater Institute,Fisheries and Oceans Canada.
61 Adoption of Genetically Engineered Crops in the U.S.: SoybeanVarieties. Data Set, Economic Research Service, UnitedStates Department of Agriculture. www.ers.usda.gov/Data/BiotechCrops/ExtentofAdoptionTable3.htm
62 Timmons at 621
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63 Timmons at 620.
64 Timmons at 648-649.
65 General Discussion. Clean, Green, Sustainable RecirculatingAquaculture Summit. Washington D.C.: hosted by Food andWater Watch. January 2009.
66 Pfeiffer, Tim. Utilization of Low-head Technology for InlandMarine Recirculating Aquaculture Systems. Clean, Green,Sustainable Recirculating Aquaculture Summit. WashingtonD.C.: hosted by Food and Water Watch. January 2009.
67 Zohar, Yonathan. Environmentally compatible, recirculatedmarine aquaculture: addressing the critical issues. Clean, Green,Sustainable Recirculating Aquaculture Summit. WashingtonD.C.: hosted by Food and Water Watch. January 2009.
68 Fuller, R.J., Solar heating systems for recirculation aquaculture.Aquacultural Engineering 36 (2007).
69 Qin, Gang., et al, Aquaculture wastewater treatment and reuseby wind-drive reverse osmosis membrane technology: A pilotstudy on Coconut Island, Hawaii. Aquacultural Engineering 32(2005).
70 Lee, Richard. Rapid growth of black sea bass Centropristis stria-ta in recirculating systems with geothermal cooling, solar heating,tilapia diet and microbial mat/seaweed lter. Clean, Green,Sustainable Recirculating Aquaculture Summit. WashingtonD.C.: hosted by Food and Water Watch. January 2009.
Craig, Steve. Sustainable Aquafeeds for Cobia Clean, Green,Sustainable Recirculating Aquaculture Summit. WashingtonD.C.: hosted by Food and Water Watch. January 2009.
Clean, Green, Sustainable Recirculating Aquaculture Summit.Washington D.C.: hosted by Food and Water Watch. January2009.
71 Timmons at 85.
72 Timmons at 120.
73 Timmons at 120.
74 Susan Bedwell. Premier Organic Farms. Clean, Green,Sustainable Recirculating Aquaculture Summit. WashingtonD.C.: hosted by Food and Water Watch. January 2009.
75 Bedwell, Susan. Personal email. Chief Financial Ofcer ofPremier Organic Farms, May 15, 2009. Email on le at Food &Water Watch.
76 Ibid.
77 Ibid.
78 Ibid.79 Ibid.
80 Ibid.
81 Ibid.
82 Ibid.
83 Process. Marvesta Shrimp Farms. Accessed on May 2, 2009.Available at: http://www.marvesta.com/process.php
84 Fritze, Scott. Personal Interview. Cofounder and owner ofMarvesta Shrimp Farms, March 28, 2008.
85 Gardner, Martin. Personal email. Director of Marketing at BlueRidge Aquaculture, May 22, 2009. Email on le at Food & WaterWatch.Nicholls, Walter. Two sides to every tilapia. WashingtonPost, August 8, 2007.
86 Ibid.
87 Tilapia. BlueRidge Aquaculture. Accessed on May 13,
2009. Available at: www.blueridgeaquaculture.com/tilapia.cfmTilapia. Op. cit.
88 Martin, Bill. Personal Interview. President of BlueRidgeAquaculture, March 26, 2008. On le at Food & Water Watch
89 Gardner, Martin. Op cit.
90 Gardner, Martin. Op cit.
91 Gardner, Martin. Op cit.
92 Gardner, Martin. Op cit.
93 Gardner, Martin. Op cit.
94 Timmons, M.B. and J.M. Ebeling. Recirculating Aquaculture. Aat 1.
95 FAO Fisheries and Aquaculture Department, Food andAgriculture Organization of the United Nations. The State ofWorld Fisheries and Aquaculture 2008 Rome, Italy. 2009 at 161
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