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On the Cover
Images from left to right
Methane flame generated from waste captured by RAS.
Photo courtesy of Dr. Yonathan Zohar at UMBI Center Of Marine Biotechnology
Lettuce and other vegetables growing in RAS aquaponic tanks at UVI.
Photo courtesy of Dr. James Rakocy at the University of the Virgin Islands in St. Croix.
Shrimp produced in a RAS facility at Blue Ridge Aquaculture.
Photo courtesy of Mr. Martin Gardner from Blue Ridge Aquaculture in Martinsville, VA.
Nile tilapia, a species often produced in RAS.
RAS tanks for raising tilapia.
Photo courtesy of Dr. Martin Schreibman at Brooklyn College, CUNY, Aquatic Research
Environmental ssessment Center (AREAC)
This report is a joint project of the Alliance for Sustainable Aquaculture and Food & Water Watch.
About the Alliance for Sustainable Aquaculture
Alliance for Sustainable Aquaculture (ASA) is a collaborative group of researchers, business owners, non-profit
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 country’s need for a clean, green, sustainable,
healthy seafood source to supplement our wild fisheries.
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www.foodandwaterwatch.org/asa
About Food & Water Watch
Food & Water Watch is a nonprofit consumer organization that works to ensure clean water and safe food. We challenge 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 organizations 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.
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Copyright © September 2009 by Food & Water Watch. All rights reserved. This report can be viewed or downloaded at
www.foodandwaterwatch.org.
Land-Based Recirculating
Aquaculture Systems
a more sustainable approach to aquaculture
Table of Contents
iv
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
Specific Commercial Case Studies
13
Conclusion
14
Endnotes
Executive Summary
This report, Land-Based Recirculating Aquaculture Systems, provides an introduction to Recirculating Aquaculture
Systems (RAS). RAS are closed-loop fish 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 fish for the United States; highlights
research, development and technical innovations in RAS; and discusses concerns and recommendations for the
future 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 fish, like tuna, cod and certain
snapper are depleted in the wild from many years of poor management, overfishing and other ecological problems
like pollution and damage to key habitat areas. There is a need to supplement wild-caught fish to meet consumer
demand for seafood. One method to produce more fish is known broadly as aquaculture — the rearing of aquatic
animals in captivity. Aquaculture is also often called “fish 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 fish farming methods, such as coastal ponds and open-ocean aquaculture (OOA), can seriously damage marine ecosystems and are far from providing the safe and sustainable seafood many consumers want.
In particular, OOA — the mass production of fish in huge floating net pens or cages in open ocean waters — raises
concerns about consumer safety, pollution of the marine environment and conflicts 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 fish and parasite escapes — all serious concerns raised with open-water aquaculture.
RAS provide a diversity of production options. Tilapia, catfish, 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 such
as 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 fish 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, fish 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 sustainable fish production, such as RAS. This report challenges natural resource managers and consumers to be more
active in helping to promote a cleaner, greener, safer domestic seafood supply by learning more about RAS and requesting grocery stores and restaurants carry RAS products rather than those from open-water aquaculture systems.
Alliance for Sustainable Aquaculture and Food & Water Watch
Lettuce and other vegetables growing in RAS aquaponic tanks at UVI.
Photo courtesy of Dr. James Rakocy at the University of the Virgin Islands in St. Croix.
Introduction
C
onsumer demand for cleaner, greener, safer seafood is on the rise. Popular species
of wild fish are depleted,1 leaving many people looking to aquaculture to help meet
the demand for seafood. Aquaculture production — the rearing of aquatic plants and
animals in captivity — is increasing worldwide; between 2004 and 2006 the annual
growth rate was 6.1 percent in volume and 11 percent in value.2 There are many forms
of aquaculture; recirculating aquaculture systems (RAS), coastal ponds and openwater net pens are a few major types. Open-water aquaculture systems are, as they
sound, open to air and water, and can therefore have a risk of air- or water-borne
contaminants.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-borne
contaminants.
What Is RAS?
Recirculating aquaculture systems (RAS) are closedloop facilities that retain and treat the water within the
system. The water in RAS flows from a fish 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 fish and parasite escapes. RAS have been under
development for the over 30 years, refining techniques
and methods to increase production, profitability and
environmental sustainability.6
Various methods can be used to clean the water from the
fish tanks and make it reusable. Some RAS fish farms
incorporate aquaponics — the practice of growing herbs
and vegetables in water — into their system. Plants need
13 elements to grow; the wastewater from the fish tanks
naturally provides 10 of these elements.7 The plants
thrive in the nutrient-rich system water, and they actually help to purify it for reuse — the plants absorb the
nutrients and the “cleaned” water can go back to the fish
tanks!
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Land-Based Recirculating Aquaculture: A More Sustainable Approach to Aquaculture
Types of RAS: Freshwater and
Saltwater
Recirculating aquaculture systems can be divided into
two main categories: freshwater and saltwater operations. Each of these can be paired with specific technologies designed to maximize efficiency within the system,
minimize effluent discharge and occasionally to work in
a symbiotic relationship with other technologies, reviewed in brief below.
Freshwater RAS
Freshwater RAS can include the production of such
fish as tilapia, catfish, eel or striped bass, among others. One innovative method explored in conjunction
with freshwater RAS is aquaponics, as described above.
Aquaponics works by allowing for the growth of plants,
fish and nitrifying bacteria simultaneously — each of
which feed off of the waste of the others to create a system 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 fish waste, which can be
fatal to fish even at very small concentrations — as little
as .08 mg/L. Aquaponic systems work by introducing
nitrifying bacteria, which feed on the ammonia in fish
waste to convert it into nitrate, which is non-toxic to the
fish and beneficial for the plants.9 Another innovation in
freshwater RAS involves the use of microalgae to reduce
2
An example of a small-scale RAS.
Photo by Eileen Flynn
the prevalence of carbon dioxide within these systems
and provide a food source to developing fish.
Saltwater RAS
Saltwater RAS can take several forms as well, and are
sometimes referred to as marine RAS. One type of system that has been researched extensively in recent years
is 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 fish density; thus, the larger the production scale, the more effluents will appear in the system
and need treatment in order to ensure the continued
growth of the fish.10 Macroalgae can accomplish this because they absorb the nutrients that are in fish waste for
their own growth, the same way that aquaponics produce
plant growth from these nutrients. The difference in marine RAS is that the seaweed is generally not intended for
consumption, and the seaweed will thrive in high-salinity 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
Alliance for Sustainable Aquaculture and Food & Water Watch
macroalgae alike — with higher productivity rates in the
warmer, brighter summer months.
Why RAS Could Be an Important Fish
Production 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 flows from the fish tank to the mechanical filter where solid waste is removed. The water then
flows into a biological filter that converts ammonia to
nitrate. Some RAS incorporate plant tanks as a biological filter – plants absorb nutrients, thus “cleaning” the
water. Other systems use special tanks that are designed
to promote good bacteria growth – the bacteria act as
a filter. After being “treated” in the mechanical and
biofiltration components, the water flows back to the fish
tank.
Biosecurity
RAS fish farms are often fully closed and entirely controlled, 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 consumers. Water supply is a regular route of pathogen entry,
so RAS water is often first disinfected or the water is
obtained from a source that does not contain fish or invertebrates 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 cleaning, completely and frequently, to reduce pathogens.13
Being self-contained and cleaner also means RAS can be
located near markets or within land-locked communities that will use the fish, 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 fish 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 especially important in saltwater systems since salt water can
be more expensive and more difficult to make or obtain
than fresh water.
Space and Production Efficiency
RAS production levels are often higher than those in other 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 fish in just nine months, compared to the
15 to 18 months it often takes for the fish raised in other
Open-Water Aquaculture
Open-water aquaculture, (when in the ocean, also known
as offshore aquaculture, ocean fish farming, open-ocean
aquaculture and other, similar terms), is the mass production of
fish in coastal ponds, or large floating pens or cages in ocean
waters. Just one farm is a large-scale operation.
While open-water fish farming is a fairly common practice
worldwide (we don’t 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 from clearing
out space to site the farm or from anchors to hold down
cages.
•
Fish in cages can spread diseases to wild fish, or escape
and intermix with wild fish, interfering with or even
overtaking natural populations.
•
Open-water fish farms allow free flow of water between
the fish enclosures and the ocean. Concentrated amounts
of fish food, wastes, diseases and any chemicals or
antibiotics that may be used in farms can flow straight into
open waters, polluting habitat and wildlife and impeding
recreational water uses like swimming and diving.
•
Chemicals used in production may remain in the fish and be
transferred to people who consume them later.
Because there are so many potential problems with open-water
farms, the United States should explore other options, like RAS.
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Land-Based Recirculating Aquaculture: A More Sustainable Approach to Aquaculture
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, vegetables, fruits, flowering plants and seaweeds as well.
RAS Factors
Water Quality and Waste Management
The critical water quality parameters in RAS are dissolved 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 fish needs to stay
alive and grow depends on the species and size of fish,
as well as the effects of the other water quality parameters.21 A fish with a higher metabolic rate will consume
DO at a higher rate. 22 Oxygen is also critical to the metabolic 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 fish and bacteria, ultimately resulting in mortalities. DO levels are monitored as water is leaving the
fish tank or the biological filter (where a large amount of
bacteria lives) to accurately access the level of DO that is
available to fish 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 these
options 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 fish and bacteria. Three sources of pure oxygen often used for RAS
are high-pressure oxygen gas, liquid oxygen and on-site
Oxygen dissolving into a RAS.
Photo by Eileen Flynn
4
Alliance for Sustainable Aquaculture and Food & Water Watch
generators.27 U-tube aerators, packed columns, low
head oxygenators and down-flow bubble contactors are
component options for diffusing pure oxygen into the
system water. These components are all designed to use
a counter-flow of water and oxygen to enhance the gasliquid interface forcing more oxygen to dissolve into the
water.28 In general, warm-water fish grow best when DO
concentrations 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 fish such as respiration rate, efficiency of feeding and
assimilation, growth, behavior and reproduction.30 Fish
are often grouped into three categories based on preferred temperature ranges: cold-water species below 60
degrees Fahrenheit, cool-water species between 60 F to
68 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 efficiency.
At Skidaway Institute of Oceanography, Dr. Richard Lee,
an emeritus professor of oceanography, uses geothermal
chilling and solar heating to regulate the temperature of
his RAS. The geothermal chilling is conducted through
a closed-loop pipe running down into the groundwater and back up to the surface (no water is exchanged
between the facility and the groundwater). The groundwater 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 approximately 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 transfer the heat they absorb from the sun to the water in the
pipes. Using this method the RAS system had temperatures 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 important tasks in RAS. The pH is directly affected by
pH testers.
Photo by Eileen Flynn
concentrations of ammonia from fish wastes. When fish
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 fish 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 equilibrium 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 maintained at a slightly lower level (around 5.5 to 6.5), where
the slightly higher acidity level helps plants to obtain nutrients. Some studies have been done in aquaponics systems to reconcile the lower optimal pH of plants with the
higher optimal pH of fish, and it has been found that a
pH 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 saltwater 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 acceptable range for health and growth of the fish. Some of
the aforementioned technologies, such as high rate algal
ponds, can act as a counterbalance to the accumulation
5
Land-Based Recirculating Aquaculture: A More Sustainable Approach to Aquaculture
of certain chemicals within an RAS and can help to balance pH levels naturally.
Alkalinity is a measure of the pH-buffering capacity
of water.36 The principle ions that contribute to alkalinity are carbonate (CO3-) and bicarbonate (HCO3-).
Supplements may be added to water to adjust the alkalinity. 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 benefit of RAS over other forms of aquaculture is the ability to capture, treat and/or utilize waste
from the system. In general, solid wastes, including
feces and uneaten feed, are filtered 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 fish fecal matter, uneaten
food and other solids from the water will never produce
fish economically.38
Nitrogen is required in small amounts by fish for good
health and growth. Nitrogen that is not utilized by fish
becomes nitrogenous waste in the system and needs to
be removed. There are several sources of nitrogenous
waste including: feces, urine, excretions from gill diffusion, uneaten food and dead and dying fish.39 The
decomposition of these nitrogenous compounds is particularly important because of the toxicity of ammonia,
nitrite and to some extent nitrate to fish.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 proportion of the non-ionized form of ammonia.42 Nitrite is
the intermediate product in the process of nitrification
of ammonia to nitrate and is toxic because it affects the
blood’s ability to carry oxygen.43 In RAS, effluent water
is passed through a biofilter containing bacteria that
converts ammonia to nitrite and finally to nitrate.44 This
conversion from ammonia and nitrite to nitrate is called
nitrification; the bacteria in this process require ample
amounts of oxygen.45 Plants in an aquaponic system will
act as the biofilter converting ammonia and nitrates. In
RAS facilities without plants in the system (aquaponics),
the biofiltration component consists of media with living
beneficial bacteria that converts harmful ammonia and
nitrite to nitrate. Algae and bacteria floating in the water
column can also convert ammonia to nitrate.46 Nitrate
is the end product of nitrification and is the least toxic; it
can be removed from the system by daily water changes
or denitrification.47 Denitrification is the process of
converting nitrate to nitrogen gas; the bacteria in this
process do not require oxygen.48
Treatment processes for recycling water at the USDA ARS National Cold Water
Marine Aquaculture Center, Franklin, ME.
Photo courtesy of Dr. Steve Summerfelt of the Freshwater Institute, Shepherdstown, WV.
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Alliance for Sustainable Aquaculture and Food & Water Watch
Basil grown in a RAS aquaponics tank at UVI.
Photo by Eileen Flynn
Carbon dioxide
Dissolved carbon dioxide is another product that can
accumulate in high-density RAS. Large-scale RAS
systems must supplement their tanks with pure oxygen
for a greater quantity of fish to be bred, but this results
in insufficient natural removal of the carbon dioxide
(CO2) that is then produced.49 (In lower-density systems,
oxygenation is generally unnecessary, as sufficient 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 acidification, which can be detrimental to fish
if the pH level drops too low. Various technologies have
been tested to reduce the amount of carbon dioxide in
the water of these high-density systems. One method of
addressing excessive carbon dioxide is the use of chemicals, which can balance pH levels and thereby eliminate
the CO2 in RAS.50 Sodium hydroxide and sodium bicarbonate 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 called
aeration 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 dissolved 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 filtration process — improve the
efficiency of carbon dioxide stripping from a recirculating 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
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Land-Based Recirculating Aquaculture: A More Sustainable Approach to Aquaculture
The overall waste-capture efficiency of a full RAS facility
can be 100 percent.53
Researchers and industry experts are developing a variety of resourceful ways to deal with the waste produced
by RAS fish farms, such as creating fertilizer for crops
and plants. Some RAS farms turn the waste into pellets
to create a feed ingredient for other fish 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, greener and safer products.
Urban Aquaculture as a CommunityBased Option
Dr. Martin Schreibman, founder and director of the
Aquatic Research and Environmental Assessment Center
at the City University of New York’s Brooklyn College,
is conducting research on RAS he calls “urban aquaculture.” Dr. Schreibman is working with RAS of various
sizes that can be run virtually anywhere, in warehouses,
on brownfield sites or right in your own home, utilizing
the hydroponic component of aquaponics to clean the
water. One aspect of his research involves “aeroponics,” in which plants are suspended above the tanks
and 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 benefits — 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 the
Virgin Islands Agricultural Experimental Station, conducts RAS aquaponic research in a large-scale system
with plants growing on floating rafts. Foam rafts float on
the surface of large water-filled 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 fish and plants) in a small setting — in fact it is in a part of a classroom at Brooklyn College!
Photo courtesy of Dr. Martin Schreibman at Brooklyn College, CUNY, Aquatic Research Environmental Assessment Center (AREAC)
8
Alliance for Sustainable Aquaculture and Food & Water Watch
beneath. Raft tanks have no size limitations. A disadvantage of raft culture — exposing the roots to zooplankton and snails that may grow in the tanks — is addressed
through the addition of ornamental fish (tetras) and
red ear sunfish to consume these pests.57 Additional
research has been done refining waste management
components and water quality needs for optimal plant
and fish growth. Dr. Rakocy’s research shows the technology 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, flowers, squash, bok choy, collard greens and
sorrel (a locally grown plant used in a popular drink) and
other crops. The UVI commercial-scale aquaponic system 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
flatfish, 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, flowers, squash,
bok choy, collard greens, sorrel, arugula, peas and various pharmaceutical plants
Fish Feed
Existing RAS farms and researchers are working to feed
their fish 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 fish used as an ingredient
in fish feed. Traditionally, large amounts of wild fish are
used to produce the pellet feed for farmed fish. Taking
prey fish from the oceans to feed farmed fish 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 fish needed to be put
into feed; finding alternative feed ingredients (including worms and algae);59 and even using waste to create a
healthy feed source.
Fish feed pellets.
Photo by Eileen Flynn
Dr Richard Lee at Skidaway Institute of Oceanography
has found a unique solution to raising carnivorous fish
without taking wild fish. At the Skidaway RAS facility Dr.
Lee grows black seabass to a market size of two pounds
in one year by feeding them whole tank-raised tilapia.
The feed conversion rate is five 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 fishmeal pellet. Feeding a tank-raised
freshwater fish to a saltwater RAS raised fish also reduces the chance of pathogen introduction.
A majority of commercial feeds use soybean as a common protein replacement for fishmeal and fish oil. There
are some concerns with using soybean, a terrestrial
protein, in fish feed. In 2009, 91 percent of soybeans
grown in the United States were genetically modified.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 researchers are looking to replace soybeans in feed with
other proteins that occur naturally in the aquatic environment, like algae, that could increase the financial
sustainability of RAS.
9
Land-Based Recirculating Aquaculture: A More Sustainable Approach to Aquaculture
Future Improvements
RAS is not yet perfect, but the benefits of a controlled,
closed system with waste management should not be
overlooked. Additional research is being done to develop 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 fish 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 diagnostic laboratory should be involved in determining the
specific disease and treatment, using chemicals that are
approved for use in food fish 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 aquaponics and facilities raising shrimp may be able to use
fewer 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 Agriculture’s Agricultural Research Service to determine the specific energy requirements for different
aspects of the treatment processes and how to get the
most efficient water treatment with the least amount of
energy.66 Dr. Yonathan Zohar, Director at University
of Maryland Biotechnology Institute’s 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 and
researchers at COMB are also working to convert algae
biomass, produced in RAS, into bio-fuel.
Both freshwater and marine RAS have been the subject of experiments to enhance energy efficiency.
Implementing solar heating for the maintenance of
proper temperature within the fish basin has been found
to reduce conventional energy requirements by 66 percent to 87 percent, depending on the regional climate
10
Lettuce and other vegetables growing in RAS aquaponic tanks at UVI.
Photo courtesy of Dr. James Rakocy at the University of the Virgin Islands in St. Croix.
where the RAS are located.68 Wind energy has also been
tested as a means to power reverse-osmosis membrane
filtration, which separates purified water from a concentrated “brine” of fish effluent, with some success.69 Many
of these technologies have been proven viable at a smallscale, and implementation on large-scale (high-density)
RAS are ongoing.
Feed Efficiency
In the production of farm-raised fish, the feed plays a
large role in determining sustainability and quality of
farmed fish. Farmed fish are often fed wild forage fish,
such as anchovies, sardines and herring, after being
processed into fishmeal or oil. These prey fish are a
crucial part of the marine ecosystem, serving as food for
marine mammals, birds and large predatory fish. Since
Alliance for Sustainable Aquaculture and Food & Water Watch
taking these fish from the oceans can disrupt food chains
and ecosystem balance, feed conversion rate is always
a concern with farm-raised fish. The ideal feed conversion is one pound or less of wild fish to raise one pound
of farmed fish. Although existing feed sources do not
always have completely efficient 1:1 conversion rates,
RAS farms and scientists are conducting research and
developing techniques that can improve feed quality and
reduce the need for wild fish. Examples of innovations
in RAS feed efficiency include finding alternative feed
ingredients, such as worms and algae, improving feed
quality by using algae to increase protein content and
raising prey fish in RAS, instead of harvesting wild forage fish, to feed larger predatory fish.70
“Organic”?
Organic foods are produced under conditions in which
all inputs are controlled. RAS is the only method of
raising fish that can completely control the production
environment. Being a closed-loop system, RAS can
better ensure fish and plants are not being exposed to
synthetic fertilizers or pesticides, growth hormones,
sewage sludge, antibiotics or any other artificial feed or
treatments. Other forms of aquaculture that allow water
to flow 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 certified organic for the plants produced.
Not a Natural Environment, but Still a
Healthy One
To achieve economic viability, RAS farms run their systems with a higher density of fish per tank than would be
found in the wild. Density depends primarily on water
quality, fish species and size.71 Overcrowding of younger
fish is avoided to allow them optimal room to grow during their rapid growth stage.72 As fish grow they may
be moved to reduce densities to maintain good water
quality and to optimize fish health and growth until they
reach market size. RAS fish farmers avoid keeping fish
at densities that can be detrimental to fish health; for example, trout raised at high densities can develop eroded
fins.73 Researchers regularly experiment with densities to
ensure optimum health and productivity.
Algae growing in tubes in RAS at COMB facility.
Photo courtesy of Dr. Yonathan Zohar at UMBI Center Of Marine Biotechnology
11
Land-Based Recirculating Aquaculture: A More Sustainable Approach to Aquaculture
Specific Commercial Case Studies
Premier Organic Farms
Premier Organic Farms combines organic growing practices in controlled ecological environments as the basis
for their state-of-the-art, eco-friendly aquaponics farming operation, which can run anywhere in the world.74
The company has done extensive research and development 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 butter 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 protein.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 fish to males (to
avoid unintentional breeding in grow out tanks before
the sex of each fish can be identified).80 Premier plans
to build commercial Pod Growing Units near strategic
markets across the United States over the next five years,
with further expansion worldwide as demand dictates.
One “Pod” is predicted to produce $43 million in revenue annually from all segments (tilapia and mixed
organic produce).81
Premier’s growing system uses 80 percent less water
than conventional agriculture.82 The company’s goals
are to produce high quality, safe food while achieving a
carbon neutral footprint.
Blue Ridge Aquaculture
Blue Ridge Aquaculture, established in 1993, produces 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 world’s largest
indoor producer of tilapia.86 Blue Ridge Aquaculture asserts that its products are free of growth hormones, pesticides, antibiotics, and synthetic chemicals.87 According
to the company’s president, Bill Martin, Blue Ridge
Aquaculture is one of few tilapia farms that hand select
broodstock for desirable characteristics, rather than using hormones.88
Blue Ridge is partnering with feed production company Marical and Virginia Tech to research low-salinity
technology and feed options for cobia in RAS.89 The
company hopes to research other marine species once
they have brought the cobia production up to commercial 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 production 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
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 filtered down
to below 50 microns and run through an ultraviolet filter
(which removes unwanted bacteria, algae and viruses).83
Co-founder Scott Fritze says that the water is 100 percent recirculating and completely bio-secure, with no
effluent and little waste. The nitrification system that
they have in place now is entirely indoors and produces
some 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 disposed of.84 Marvesta does not use antibiotics, hormones,
pesticides or chemicals of any kind.
Computer rendering of the 4,800 L/min water recirculating system at the
Conservation Fund Freshwater Institute.
Summerfelt, S.T., Sharrer, M.J., Hollis, J., Gleason, L.E., Summerfelt,
S. R. 2004. Dissolved ozone destruction using ultraviolet irradiation in
a recirculating salmonid culture system. Aquacultural Engineering 32,
209-224. Drawing courtesy of Marine Biotech Inc. (Beverly, MA).
12
Alliance for Sustainable Aquaculture and Food & Water Watch
Fish waste being distributed by a manure spreader
Summerfelt, S.T. and B.J. Vinci. (2008). Better management practices for recirculating systems. Pages 389-426 in C.S. Tucker
and J.A. Hargreaves (editors), Environmental Best Management Practices for Aquaculture. Blackwell Publishing: Ames, Iowa
Conclusion
Consumers love seafood, and with wild fish stocks depleted, aquaculture is likely to be supplying increasing
amounts of fish for food. However, not all fish farming
methods are equal. In order to ensure safer and more
sustainable seafood, consumers are more regularly asking about how their fish was produced before making
seafood choices. Common forms of aquaculture, such
as open-water systems, can pollute the marine environment with chemicals and waste, and may produce seafood contaminated with pesticides and antibiotics. These
are not acceptable factors for most consumers seeking
greener, more healthful options.
in this report, are just a few examples of successful companies that are producing RAS seafood.
RAS, on the other hand, are closed, controlled, biosecure systems. Since RAS retain and treat water within
the system, they reduce waste discharges and the need
for chemicals and antibiotics. RAS can be efficient in
production and space usage and can range from smallscale to commercial operations — growing a variety of
different fish and plants.
Federal and State governments should increase funding
to RAS researchers to help provide consumers with a
cleaner, greener, safer seafood aquaculture option.
RAS are currently operating in the United States. In
fact, RAS have been under development for over 30
years, refining techniques and methods to increase production, profitability 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
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 fish.
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. government needs to play a vital role in promoting opportunities to develop cleaner, greener, safer aquaculture in the
United States, such as RAS. 95
Recommendations
If standards must be set for an organic label for fish, RAS
raised fish should viewed as the only true option, due to
the controlled, closed-loop nature of RAS.
13
Land-Based Recirculating Aquaculture: A More Sustainable Approach to Aquaculture
Endnotes
1
2
3
4
5
6
7
8
9
10
11
12
13
14
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
14
Fishwatch.gov
FAO Fisheries and Aquaculture Department, Food and
Agriculture Organization of the United Nations. “The State of
World Fisheries and Aquaculture 2008” Rome, Italy. 2009 at 16.
Timmons, M.B. and J.M. Ebeling. (2007) “Recirculating
Aquaculture.” Cayuga Aqua Ventures at 3.
Timmons at 30.
Timmons at 6.
Timmons at 1.
Rakocy, James. “The UVI Aquaponic System.” Clean, Green,
Sustainable Recirculating Aquaculture Summit. Washington
D.C.: hosted by Food and Water Watch. January 2009.
Tyson, R.V. et al, “Effect of Water pH on Yield and Nutritional
Status of Greenhouse Cucumber Grown in Recirculating
Hydroponics.” Journal of Plant Nutrition 31.11 (2008): 2019
Ibid.
Metaxa, E., et al, “High rate algal pond treatment for water reuse
in a marine fish recirculation system: Water purification and fish
health.” Aquaculture 252 (2005).
Pagand, P. et al, “The use of high rate algal ponds for the treatment of marine effluent from a recirculating fish rearing system.”
Aquaculture Research 31 (2000).
Timmons at 621
Timmons at 620.
Torsten, E.I. Wik, et al. “Integrated dynamic aquaculture and
wastewater treatment modeling for recirculating aquaculture
systems.” Aquaculture. 287. 2009 at 361-370.
Timmons at 7.
Zohar, Yonathan. “Environmentally compatible, recirculated
marine aquaculture: addressing the critical issues.” Clean, Green,
Sustainable Recirculating Aquaculture Summit. Washington
D.C.: hosted by Food and Water Watch. January 2009.
Conversion of information from hectares to acres by Food &
Water Watch from: Moss, Shawn. “An integrated approach
to sustainable shrimp aquaculture in the U.S.” Clean, Green,
Sustainable Recirculating Aquaculture Summit. Washington
D.C.: hosted by Food and Water Watch. January 2009. Samocha,
Tzachi. “Overview of some sustainable, super-intensive microbial biofloc-rich shrimp production systems used by Gulf Coast
Research Lab, Waddell Mariculture Center and AgriLife Research
Mariculture Lab.” Clean, Green, Sustainable Recirculating
Aquaculture Summit. Washington D.C.: hosted by Food and
Water Watch. January 2009.
Timmons at 39.
Timmons at 47.
Timmons at 88.
Timmons at 88.
Timmons at 90.
Timmons at 89.
Timmons at 412.
Timmons at 413.
Timmons at 413.
Timmons at 413-426.
Timmons at 50.
Timmons at 51.
Timmons at 51.
Lee, Richard. “Rapid growth of black sea bass Centropristis striata in recirculating systems with geothermal cooling, solar heating,
tilapia diet and microbial mat/seaweed filter.” Clean, Green,
Sustainable Recirculating Aquaculture Summit. Washington
D.C.: hosted by Food and Water Watch. January 2009.
33 Lee, Richard. “Rapid growth of black sea bass Centropristis striata in recirculating systems with geothermal cooling, solar heating,
tilapia diet and microbial mat/seaweed filter.” Clean, Green,
Sustainable Recirculating Aquaculture Summit. Washington
D.C.: hosted by Food and Water Watch. January 2009.
34 Neori, Amir, et al, “Biogeochemical processes in intensive
zero-effluent marine fishculture with recirculating aerobic and
anaerobic biofilters.” Journal of Experimental Marine Biology
and 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 carbon
dioxide stripping columns in a coldwater recirculating system.”
Aquacultural Engineering 28 (2003).
50 Summerfelt, Steven T., et al, “Oxygenation and carbon dioxide
control in water reuse systems.” Aquacultural Engineering 22
(2000).
51 Summerfelt, et al, “Evaluation of full-scale carbon dioxide stripping columns,” 2003.
52 Summerfelt, et al, “Oxygenation and carbon dioxide control,”
2000.
53 Timmons at 10.
54 Zohar, Yonathan. “Environmentally compatible, recirculated
marine aquaculture: addressing the critical issues.” Clean, Green,
Sustainable Recirculating Aquaculture Summit. Washington
D.C.: hosted by Food and Water Watch. January 2009.
55 Schreibman, Martin. “Urban Aquaculture: The promises and
constraints.” Clean, Green, Sustainable Recirculating Aquaculture
Summit. Washington D.C.: hosted by Food and Water Watch.
January 2009.
56 Schreibman, Martin. “Urban Aquaculture: The promises and
constraints.” Clean, Green, Sustainable Recirculating Aquaculture
Summit. Washington D.C.: hosted by Food and Water Watch.
January 2009.
57 Rakocy, James. “The UVI Aquaponic System.” Clean, Green,
Sustainable Recirculating Aquaculture Summit. Washington
D.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 Aquatic
Population: A Whole Ecosystem Study,” Freshwater Institute,
Fisheries and Oceans Canada.
61 “Adoption of Genetically Engineered Crops in the U.S.: Soybean
Varieties.” Data Set, Economic Research Service, United
States Department of Agriculture. www.ers.usda.gov/Data/
BiotechCrops/ExtentofAdoptionTable3.htm
62 Timmons at 621
Alliance for Sustainable Aquaculture and Food & Water Watch
63 Timmons at 620.
64 Timmons at 648-649.
65 “General Discussion.” Clean, Green, Sustainable Recirculating
Aquaculture Summit. Washington D.C.: hosted by Food and
Water Watch. January 2009.
66 Pfeiffer, Tim. “Utilization of Low-head Technology for Inland
Marine Recirculating Aquaculture Systems.” Clean, Green,
Sustainable Recirculating Aquaculture Summit. Washington
D.C.: hosted by Food and Water Watch. January 2009.
67 Zohar, Yonathan. “Environmentally compatible, recirculated
marine aquaculture: addressing the critical issues.” Clean, Green,
Sustainable Recirculating Aquaculture Summit. Washington
D.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 reuse
by wind-drive reverse osmosis membrane technology: A pilot
study on Coconut Island, Hawaii.” Aquacultural Engineering 32
(2005).
70 Lee, Richard. “Rapid growth of black sea bass Centropristis striata in recirculating systems with geothermal cooling, solar heating,
tilapia diet and microbial mat/seaweed filter.” Clean, Green,
Sustainable Recirculating Aquaculture Summit. Washington
D.C.: hosted by Food and Water Watch. January 2009.
Craig, Steve. “Sustainable Aquafeeds for Cobia” Clean, Green,
Sustainable Recirculating Aquaculture Summit. Washington
D.C.: hosted by Food and Water Watch. January 2009.
Clean, Green, Sustainable Recirculating Aquaculture Summit.
Washington D.C.: hosted by Food and Water Watch. January
2009.
71 Timmons at 85.
72 Timmons at 120.
73 Timmons at 120.
74 Susan Bedwell. “Premier Organic Farms.” Clean, Green,
Sustainable Recirculating Aquaculture Summit. Washington
D.C.: hosted by Food and Water Watch. January 2009.
75 Bedwell, Susan. Personal email. Chief Financial Officer of
Premier Organic Farms, May 15, 2009. Email on file 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 of
Marvesta Shrimp Farms, March 28, 2008.
85 Gardner, Martin. Personal email. Director of Marketing at Blue
Ridge Aquaculture, May 22, 2009. Email on file at Food & Water
Watch.Nicholls, Walter. “Two sides to every tilapia.” Washington
Post, August 8, 2007.
86 Ibid.
87 “Tilapia.” BlueRidge Aquaculture. Accessed on May 13,
2009. Available at: www.blueridgeaquaculture.com/tilapia.
cfm“Tilapia.” Op. cit.
88 Martin, Bill. Personal Interview. President of BlueRidge
Aquaculture, March 26, 2008. On file 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.” A
at 1.
95 FAO Fisheries and Aquaculture Department, Food and
Agriculture Organization of the United Nations. “The State of
World Fisheries and Aquaculture 2008” Rome, Italy. 2009 at 161.
15